LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 LM3554 Synchronous Boost Converter with 1.2A Dual High Side LED Drivers and I2CCompatible Interface Check for Samples: LM3554 FEATURES 1 * * 2 * * * * * * * * * * * * Dual High Side Current Sources Grounded Cathode Allowing for Better Heat Sinking and LED Routing >90% Efficiency Ultra-Small Solution Size: < 23mm2 Four Operating Modes: Torch, Flash, LED Indicator and Voltage Output Accurate and Programmable LED Current from 37.5mA to 1.2A Programmable 4.5V or 5.0V Constant Output Voltage Hardware Flash and Torch Enable LED Thermal Sensing and Current Scaleback Software Selectable Input Voltage Monitor Programmable Flash Timeout Dual Synchronization Inputs for RF Power Amplifier Pulse Events Open and Short LED Detection Active High Hardware Enable for Protection Against System Faults * * 400kHz I2C-Compatible Interface 16-Bump (1.7mm x 1.7mm x 0.6mm) DSBGA APPLICATIONS * * * Camera Phone LED Flash Controller Class D Audio Amplifier Power LED Current Source Biasing DESCRIPTION The LM3554 is a 2MHz fixed frequency, current mode synchronous boost converter. The device is designed to operate as a dual 600mA (1.2A total) constant-current driver for high-current white LEDs, or as a regulated 4.5V or 5V voltage source. The dual high-side current sources allow for grounded cathode LED operation. An adaptive regulation method ensures the current source for each LED remains in regulation and maximizes efficiency. Typical Application Circuits 2.2 PH 5.1 mm 4.5V or 5V DC Power Rail SW .5V 5.5V IN OUT 4.7 PF HWEN SCL SDA LM3554 4.7 PF 4.5 mm VBIAS LED1 LED2 STROBE TX1/TORCH/ LEDI/NTC GPIO1 ENVM/TX2 /GPIO GND D2 Indicator LED Flash LEDs D1 RBIAS 0.1 PF 2 k: Thermistor HWEN ENVM/TX2/GPIO2 /TORCH/GPIO1 Figure 1. Typical Application Circuit Figure 2. Example Layout 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2009-2013, Texas Instruments Incorporated LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com DESCRIPTION (CONTINUED) The main features include: an I2C-compatible interface for controlling the LED current or the desired output voltage, a hardware Flash enable input for direct triggering of the Flash pulse, and dual TX inputs which force the Flash pulse into a low-current Torch mode allowing for synchronization to RF power amplifier events or other high-current conditions. Additionally, an active high hardware enable (HWEN) input provides a hardware shutdown during system software failures. Five protection features are available within the LM3554 including a software selectable input voltage monitor, an internal comparator for interfacing with an external temperature sensor, four selectable current limits to ensure the battery current is kept below a predetermined peak level, an over-voltage protection feature to limit the output voltage during LED open circuits, and an output short circuit protection which limits the output current during shorts to GND. Additionally, the device provides various fault indicators including: a thermal fault flag indicating the LED temperature has tripped the thermal threshold, a flag indicating a TX event has occurred, a flag indicating the flash timeout counter has expired, a flag indicating the devices die temperature has reached the thermal shutdown threshold, and a flag indicating an open or short LED. Table 1. Application Circuit Component List Component Manufacturer Value Part Number Size (mm) Rating L TOKO 2.2H FDSE0312-2R2M 3x3x1.2 2.3A(0.2) COUT Murata 4.7F/10F GRM188R60J475M, or GRM188R60J106M 1.6x0.8x0.8 (0603) 6.3V CIN Murata 4.7F GRM185R60J475M 1.6x0.8x0.8 (0603) 6.3V LEDs Lumiled LXCL-PWF4 1.5A Top View A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3 C4 D1 D2 D3 D4 Connection Diagram PIN DESCRIPTIONS Pin Name A1 LED1 High-Side Current Source Output for Flash LED. A2, B2 OUT Step-Up DC/DC Converter Output. A3, B3 SW Drain Connection for Internal NMOS and Synchronous PMOS Switches. A4, B4 GND Ground LED2 High-Side Current Source Output for Flash LED. B1 C1 C2 LEDI/NTC Configurable as a High-Side Current Source Output for Indicator LED or Threshold Detector for LED Temperature Sensing. TX1/TORCH/GPIO Configurable as a RF Power Amplifier Synchronization Control Input (TX1), a Hardware Torch 1 Enable (TORCH), or a programmable general-purpose logic Input/Output (GPIO1). C3 STROBE C4 IN D1 2 Function Active High Hardware Flash Enable. Drive STROBE high to turn on Flash pulse. Input Voltage Connection. Connect IN to the input supply, and bypass to GND with a minimum 4.7F ceramic capacitor. ENVM/TX2/GPIO2 Configurable as an Active High Voltage Mode Enable (ENVM), Dual Polarity Power Amplifier /INT Synchronization Input (TX2), or Programmable General Purpose Logic Input/Output (GPIO2). Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 PIN DESCRIPTIONS (continued) Pin Name D2 SDA Serial Data Input/Output. Function D3 SCL Serial Clock Input. D4 HWEN Active Low Hardware Reset. These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) (3) VIN, VSW, VOUT -0.3V to 6V VSCL, VSDA, VHWEN, VSTROBE, VTX1/TORCH, VENVM/TX2, VLED1, VLED2, VLEDI/NTC -0.3V to to (VIN+0.3V) w/ 6.0V max Continuous Power Dissipation (4) Internally Limited Junction Temperature (TJ-MAX) +150C Storage Temperature Range -65C to +150C (5) Maximum Lead Temperature (Soldering) (1) (2) (3) (4) (5) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits and associated test conditions, see Electrical Characteristics. All voltages are with respect to the potential at the GND pin. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=150C (typ.) and disengages at TJ=135C (typ.). For detailed soldering specifications and information, please refer to Application Note AN-1112: DSBGA Wafer Level chip Scale Package SNVA009 Operating Ratings (1) (2) VIN 2.5V to 5.5V Junction Temperature (TJ) Ambient Temperature (TA) (1) (2) (3) -30C to +125C (3) -30C to +85C Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits and associated test conditions, see Electrical Characteristics. All voltages are with respect to the potential at the GND pin. In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = +125C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to-ambient thermal resistance of the part/package in the application (JA), as given by the following equation: TA-MAX = TJ-MAX-OP - (JA x PD-MAX). Thermal Properties Junction-to-Ambient Thermal Resistance (JA), YFQ0016 Package (1) (1) 60C/W Junction-to-ambient thermal resistance (JA) is taken from a thermal modeling result, performed under the conditions and guidelines set forth in the JEDEC standard JESD51-7. The test board is a 4-layer FR-4 board measuring 102mm x 76mm x 1.6mm with a 2x1 array of thermal via's. The ground plane on the board is 50mm x 50mm. Thickness of copper layers are 36m/18m/18m/36m (1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22C, still air. Power dissipation is 1W. Electrical Characteristics Limits in standard typeface are for TA = +25C. Limits in boldface type apply over the full operating ambient temperature range (-30C TA +85C). Unless otherwise specified, VIN = 3.6V, VHWEN = VIN. (1) (2) Symbol Parameter Conditions Min Typ Max Units Current Source Specifications (1) (2) All voltages are with respect to the potential at the GND pin. Min and Max limits are ensured by design, test, or statistical analysis. Typical (Typ) numbers are not ensured, but do represent the most likely norm. Unless otherwise specified, conditions for typical specifications are: VIN = 3.6V and TA = +25C. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 3 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Electrical Characteristics (continued) Limits in standard typeface are for TA = +25C. Limits in boldface type apply over the full operating ambient temperature range (-30C TA +85C). Unless otherwise specified, VIN = 3.6V, VHWEN = VIN. (1)(2) Symbol ILED VHR IMATCH Parameter Current Source Accuracy Conditions 600mA Flash LED Setting, VOUT = VIN Min Typ Max ILED1+ILED2 1128 1200 1284 ILED1 or ILED2 541 600 657 17mA Torch Current Setting, ILED1+ILED2 VHR = 500mV Units mA 30.4 33.8 37.2 Current Source Regulation 600mA setting, VOUT = 3.75V Voltage (VOUT VLED) 300 mV LED Current Matching 0.35 % 600mA setting, VLED = 3.2V Step-Up DC/DC Converter Specifications VREG Output Voltage Accuracy 2.7V VIN 4.2V, IOUT = 0mA, VENVM = VIN, OV bit = 0 4.8 5 5.2 On Threshold, 2.7V VIN 5.5V 5.4 5.6 5.7 VOVP Output OverVoltage Protection Trip Point (3) RPMOS RNMOS ICL IOUT_SC ILED/NTC VTRIP fSW IQ (3) (4) 4 V V Off Threshold 5.3 PMOS Switch On-Resistance IPMOS = 1A 150 m NMOS Switch On-Resistance INMOS = 1A 150 m Switch Current Limit (4) Output Short Circuit Current Limit Indicator Current CL bits = 00 0.711 1.05 CL bits = 01 1.295 1.51 1.8 CL bits = 10 1.783 1.99 2.263 CL bits = 11 2.243 2.45 2.828 VOUT < 2.3V LEDI/NTC bit = 0 1.373 550 IND1, IND0 bits = 00 2.3 IND1, IND0 bits = 01 4.6 IND1, IND0 bits = 10 6.9 IND1, IND0 bits = 11 8.2 A mA mA Comparator Trip Threshold LEDI/NTC bit = 1, 2.7V VIN 5.5V 0.947 1.052 1.157 V Switching Frequency 2.7V VIN 5.5V 1.75 2 2.23 MHz Quiescent Supply Current Device Not Switching 630 A The typical curve for Over-Voltage Protection (OVP) is measured in closed loop using the typical application circuit . The OVP value is found by forcing an open circuit in the LED1 and LED2 path and recording the peak value of VOUT. The value given in the Electrical Table is found in an open loop configuration by ramping the voltage at OUT until the OVP comparator trips. The closed loop data can appear higher due to the stored energy in the inductor being dumped into the output capacitor after the OVP comparator trips. At worst case is an open circuit condition where the output voltage can continue to rise after the OVP comparator trips by approximately IINxsqrt(L/COUT). The typical curve for Current Limit is measured in closed loop using the typical application circuit by increasing IOUT until the peak inductor current stops increasing. The value given in the Electrical Table is measured open loop and is found by forcing current into SW until the current limit comparator threshold is reached. Closed loop data appears higher due to the delay between the comparator trip point and the NFET turning off. This delay allows the closed loop inductor current to ramp higher after the trip point by approximately 20ns x VIN/L Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Electrical Characteristics (continued) Limits in standard typeface are for TA = +25C. Limits in boldface type apply over the full operating ambient temperature range (-30C TA +85C). Unless otherwise specified, VIN = 3.6V, VHWEN = VIN. (1)(2) Symbol Parameter ISHDN Shutdown Supply Current tTX VIN_TH Conditions Min Typ Max Units 2.7V VIN 5.5V 3.5 6.6 A Flash-to-Torch LED Current Settling Time TX_ Low to High, ILED1 + ILED2 = 1.2A to 180mA 20 VIN Monitor Trip Threshold VIN Falling, VIN Monitor Register = 0x01 (Enabled with VIN_TH = 3.1V) 2.95 3.09 s 3.23 V 0 0.4 V 1.2 VIN V 400 mV TX1/TORCH/GPIO1, STROBE, HWEN, ENVM/TX2/GPIO2 Voltage Specifications VIL Input Logic Low 2.7V VIN 5.5V VIH Input Logic High 2.7V VIN 5.5V VOL Output Logic Low ILOAD = 3mA, 2.7V VIN 5.5V RTX1/TORCH Internal Pulldown Resistance at TX1/TORCH 300 k RSTROBE Internal PullDown Resistance at STROBE 300 k I2C-Compatible Voltage Specifications (SCL, SDA) VIL Input Logic Low 2.7V VIN 5.5V VIH Input Logic High 2.7V VIN 5.5V VOL Output Logic Low (SCL) ILOAD = 3mA, 2.7V VIN 5.5V 0 0.4 V 1.22 VIN V 400 mV I2C-Compatible Timing Specifications (SCL, SDA) -- See Figure 3 1/t1 SCL Clock Frequency t2 Data In Setup Time to SCL High t3 Data Out Stable After SCL Low t4 t5 400 kHz 100 ns 0 ns SDA Low Setup Time to SCL Low (Start) 160 ns SDA High Hold Time After SCL High (Stop) 160 ns Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 5 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com t1 SCL t5 t4 SDA_IN t2 SDA_OUT t3 Figure 3. I2C Timing 6 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Typical Performance Characteristics VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10F, CIN = 4.7F, L = FDSE0312-2R2 (2.2H, RL = 0.15), TA = +25C unless otherwise specified. LED Efficiency vs VIN (Single LED, L = TOKO FDSE0312-2R2) LED Efficiency vs VIN (Dual LEDs, L = TOKO FDSE0312-2R2) Figure 4. Figure 5. Input Current vs VIN (Single LED, L = TOKO FDSE0312-2R2) LED Efficiency vs VIN (Single LED, L = Coilcraft LPS4018-222) Figure 6. Figure 7. LED Efficiency vs VIN (Dual LED's, L = Coilcraft LPS4018-222) Input Current vs VIN (Single LED, L = Coilcraft LPS4018-222) Figure 8. Figure 9. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 7 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10F, CIN = 4.7F, L = FDSE0312-2R2 (2.2H, RL = 0.15), TA = +25C unless otherwise specified. (1) 8 Efficiency vs IOUT (Voltage Output Mode, VOUT = 5V) Efficiency vs VIN (Voltage Output Mode, VOUT = 5V) Figure 10. Figure 11. VOUT vs IOUT (Voltage Output Mode, VOUT = 5V) VOUT vs VIN (Voltage Output Mode, VOUT = 5V) Figure 12. Figure 13. Torch Current Matching vs Code (VIN= 3.6V, VLED1, VLED2 = 3.2V, TA = -40C to +85C, (1) ) Torch Current vs VIN (VLED1, VLED2 = 3.2V, TA = +25C, 75mA setting) Figure 14. Figure 15. Current Matching = Absolute Value((ILED1 - ILED2)/(ILED1 + ILED2)) x 100 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Typical Performance Characteristics (continued) VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10F, CIN = 4.7F, L = FDSE0312-2R2 (2.2H, RL = 0.15), TA = +25C unless otherwise specified. (2) Torch Current vs VIN (VLED1, VLED2 = 3.2V, TA = +85C, 75mA setting) Torch Current vs VIN (VLED1, VLED2 = 3.2V, TA = -40C, 75mA setting) Figure 16. Figure 17. Flash Current Matching vs Code (VIN= 3.6V, VLED1, VLED2 = 3.2V, TA = -40C to +85C, (2) Flash Current vs VIN (VLED1, VLED2 = 3.2V, TA = +25C, 600mA setting) Figure 18. Figure 19. Flash Current vs VIN (VLED1, VLED2 = 3.2V, TA = +85C, 600mA setting) Flash Current vs VIN (VLED1, VLED2 = 3.2V, TA = -40C, 600mA setting) Figure 20. Figure 21. Current Matching = Absolute Value((ILED1 - ILED2)/(ILED1 + ILED2)) x 100 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 9 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10F, CIN = 4.7F, L = FDSE0312-2R2 (2.2H, RL = 0.15), TA = +25C unless otherwise specified. Switching Frequency vs VIN Shutdown Current vs VIN (VHWEN = 0V) Figure 22. Figure 23. Active (Non-Switching) Supply Current vs VIN (VLED = 1.5V) Active (Switching) Supply Current vs VIN (VOUT = 5V, IOUT = 400mA) Figure 24. Figure 25. Closed Loop Current Limit vs VIN (Flash Duration Register bits [6:5] = 00, (3) ) Figure 26. (3) 10 Closed Loop Current Limit vs VIN (Flash Duration Register bits [6:5] = 01, (3) ) Figure 27. The typical curve for Current Limit is measured in closed loop using the typical application circuit by increasing IOUT until the peak inductor current stops increasing. The value given in the Electrical Table is measured open loop and is found by forcing current into SW until the current limit comparator threshold is reached. Closed loop data appears higher due to the delay between the comparator trip point and the NFET turning off. This delay allows the closed loop inductor current to ramp higher after the trip point by approximately 20ns x VIN/L Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Typical Performance Characteristics (continued) VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10F, CIN = 4.7F, L = FDSE0312-2R2 (2.2H, RL = 0.15), TA = +25C unless otherwise specified. Closed Loop Current Limit vs VIN (Flash Duration Register bits [6:5] = 10, (3) ) Figure 28. (3) ) Figure 29. VIN Monitor Thresholds vs Temperature (4) Closed Loop Current Limit vs VIN (Flash Duration Register bits [6:5] = 11, OVP Thresholds vs VIN (4) Figure 30. Figure 31. Short Circuit Current Limit vs VIN Indicator Current vs VIN, VLEDI = 2V (Torch Brightness Register bits[7:6] = 00) Figure 32. Figure 33. The typical curve for Over-Voltage Protection (OVP) is measured in closed loop using the typical application circuit . The OVP value is found by forcing an open circuit in the LED1 and LED2 path and recording the peak value of VOUT. The value given in the Electrical Table is found in an open loop configuration by ramping the voltage at OUT until the OVP comparator trips. The closed loop data can appear higher due to the stored energy in the inductor being dumped into the output capacitor after the OVP comparator trips. At worst case is an open circuit condition where the output voltage can continue to rise after the OVP comparator trips by approximately IINxsqrt(L/COUT). Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 11 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10F, CIN = 4.7F, L = FDSE0312-2R2 (2.2H, RL = 0.15), TA = +25C unless otherwise specified. Indicator Current vs VIN, VLEDI = 2V (Torch Brightness Register bits[7:6] = 01) Indicator Current vs VIN, VLEDI = 2V (Torch Brightness Register bits[7:6] = 10) Figure 34. Figure 35. Indicator Current vs VIN, VLEDI = 2V (Torch Brightness Register bits[7:6] = 11) NTC Comparator Trip Threshold vs VIN Figure 36. Figure 37. Startup into Flash Mode Single LED IFLASH = 1.2A Startup into Torch Mode Single LED, Hardware Torch Mode, 90mA Torch Setting ITORCH = 180mA Channel 1: VOUT (2V/div) Channel 4: ILED (500mA/div) Channel 2: IL (500mA/div) Channel 3: STROBE (5V/div) Time Base: (100s/div) Channel 1: VOUT (2V/div) Channel 4: ILED (100mA/div) Channel 2: IL (500mA/div) Channel 3: TX1 (5V/div) Time Base: (100s/div) Figure 38. 12 Figure 39. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Typical Performance Characteristics (continued) VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10F, CIN = 4.7F, L = FDSE0312-2R2 (2.2H, RL = 0.15), TA = +25C unless otherwise specified. Torch Mode to Flash Mode Transition Single LED ITORCH = 295mA, IFLASH = 1.2A Channel 1: VOUT (5V/div) Channel 4: ILED (500mA/div) Channel 2: IL (1A/div) Channel 3: STROBE (5V/div) Time Base: (100s/div) TX1 Interrupt Operation, TX1 Rising Single LED IFLASH = 1.2A, ITORCH = 180mA Channel 1: VOUT (2V/div) Channel 4: ILED (500mA/div) Channel 2: IL (1A/div) Channel 3: TX1 (5V/div) Time Base: (20s/div) Figure 40. Figure 41. TX1 Interrupt Operation, TX1 Falling Single LED IFLASH = 1.2A, ITORCH = 180mA Line Transient (LED Mode, Single LED, IFLASH = 1.2A) Channel 1: VOUT (2V/div) Channel 4: ILED (500mA/div) Channel 2: IL (1A/div) Channel 3: TX1 (5V/div) Time Base: (20s/div) Channel 3: VIN (1V/div) Channel 4: ILED (500mA/div) Channel 2: IL (1A/div) Time Base: (400s/div) Figure 42. Figure 43. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 13 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Typical Performance Characteristics (continued) VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10F, CIN = 4.7F, L = FDSE0312-2R2 (2.2H, RL = 0.15), TA = +25C unless otherwise specified. Load Transient VIN = 3.6V (Voltage Output Mode, VOUT = 5V) Channel 1: VOUT (500mV/div, AC Coupled) Channel 4: IOUT (200mA/div) Channel 2: IL (500mA/div) Time Base: (40s/div) Figure 44. Line Transient IOUT = 500mA (Voltage Output Mode, VOUT = 5V) Channel 3 (Top Trace): VIN (1V/div) Channel 1: VOUT (100mV/div, AC Coupled) Channel 2: IL + IIN (500mA/div) Time Base: (200s/div) Figure 45. Flash Pulse to HWEN Low Single LED, ILED = 1.2A Channel 1: VOUT (2V/div) Channel 4: ILED (500mA/div) Channel 2: IL (1A/div) Channel 3: HWEN (5V/div) Time Base: (20s/div) Flash Pulse to Flash Pulse + VOUT Mode Single LED, ILED = 1.2A, VOUT = 5V Channel 1: VOUT (2V/div) Channel 4: ILED (500mA/div) Channel 2: IL (1A/div) Channel 3: ENVM (5V/div) Time Base: (100s/div) Figure 46. 14 Figure 47. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Typical Performance Characteristics (continued) VIN = 3.6V, LEDs are Lumiled PWF-4, COUT = 10F, CIN = 4.7F, L = FDSE0312-2R2 (2.2H, RL = 0.15), TA = +25C unless otherwise specified. Flash Pulse + VOUT to Flash Pulse Single LED, ILED = 1.2A, VOUT = 5V NTC Mode Response Single LED, ILED = 1.2A Circuit of Figure 74 (R(T) = 100k (@+25C), R3 = 9k) Channel 3: NTC Pin Voltage (500mV/div) Channel 4: ILED (500mA/div) Time Base: (200ms/div) Channel 1: VOUT (2V/div) Channel 4: ILED (500mA/div) Channel 2: IL (1A/div) Channel 3: ENVM (5V/div) Time Base: (100s/div) Figure 48. Figure 49. VIN Monitor Response Single LED, ILED = 1.2A 3.1V UVLO Setting Channel 3: VIN (1V/div) Channel 4: ILED (500mA/div) Time Base: (100ms/div) Figure 50. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 15 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com BLOCK DIAGRAM SW Over Voltage Comparator + - IN 2 MHz Oscillator VREF 150 m: VREF OUT ILED1 ILED2 PWM Control ILEDI 150 m LEDI/ NTC Thermal Shutdown +150oC Error Amplifier + - ISET LED1 Reference Mode Select LED2 VREF + + - Current Sense/Current Limit VTRIP Feedback Mode Select Max VLED Slope Compensation SDA Control Logic/ Soft-Start I2C Interface SCL HWEN TX1/TORCH/ GPIO1 STROBE ENVM/TX2/ GPIO2 GND Overview The LM3554 is a high-power white LED flash driver capable of delivering up to 1.2A of LED current into a single LED, or up to 600mA into two parallel LEDs. The device incorporates a 2MHz constant frequency, synchronous, current mode PWM boost converter, and two high-side current sources to regulate the LED current over the 2.5V to 5.5V input voltage range. The LM3554 operates in two modes: LED mode or constant Voltage Output mode. In LED mode when the output voltage is greater than VIN - 150mV, the PWM converter switches and maintains at least 300mV (VHR) across both current sources (LED1 and LED2). This minimum headroom voltage ensures that the current sinks remain in regulation. When the input voltage is above VLED + VHR, the device operates in Pass mode with the device not switching and the PFET on continuously. In Pass mode the difference between (VIN - ILEDxRON_P) and VLED is dropped across the current sources. If the device is operating in Pass mode, and VIN drops to a point that forces the device into switching, the LM3554 will make a one-time decision to jump into switching mode. The LM3554 remains in switching mode until the device is shutdown and re-enabled. This is true even if VIN were to rise back above VLED + 300mV during the current Flash or Torch cycle. This prevents the LED current from oscillating when VIN is operating close to VOUT. In Voltage Output mode the LM3554 operates as a voltage output boost converter with selectable output voltages of 4.5V and 5V. In this mode the LM3554 is able to deliver up to typically 5W of output power. At light loads and in Voltage Output mode the PWM switching converter changes over to a pulsed frequency regulation mode and only switches as necessary to ensure proper LED current or output voltage regulation. This allows for improved light load efficiency compared to converters that operate in fixed-frequency PWM mode at all load currents. 16 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Additional features of the LM3554 include 4 logic inputs, an internal comparator for LED thermal sensing, and a low-power indicator LED current source. The STROBE input provides a hardware Flash mode enable. The ENVM/TX2/GPIO2 input is configurable as a hardware Voltage Output mode enable (ENVM), an active high Flash interrupt that forces the device from FLASH mode to a low-power TORCH mode (TX2), or as a programmable logic input/output (GPIO2). The TX1 input is configurable as an active high Flash interrupt that forces the device from FLASH mode to a low-power TORCH mode (TX1), as a hardware Torch mode enable (TORCH), or as a programmable logic input/output (GPIO1) . The HWEN input provides for an active low hardware shutdown of the device. Finally, the LEDI/NTC pin is configurable as a low-power indicator LED driver (LEDI), or as a threshold detector for thermal sensing (NTC). In NTC mode when the threshold (VTRIP) at the LEDI/NTC pin is crossed (VLEDI/NTC falling), the Flash pulse is forced to the Torch current setting, or into shutdown depending on the NTC Shutdown bit setting . Control of the LM3554 is done via an I2C-compatible interface. This includes switch-over from LED to Voltage Output mode, adjustment of the LED current in TORCH mode, adjustment of the LED current in FLASH mode, adjustment of the indicator LED currents, changing the flash LED current duration, changing the switch current limit. Additionally, there are 5 flag bits that can be read back indicating flash current timeout, over-temperature condition, LED failure (open or short), LED thermal failure, and an input voltage fault. STARTUP Turn on of the LM3554 is done through bits [2:0] of the Torch Brightness Register (0xA0), bits [2:0] of the Flash Brightness Register (0xB0), the ENVM input, or the STROBE input. Bits [1:0] of the Torch Brightness Register or Flash Brightness Register enables/disables the current sources (LED1, LED2, and LEDI). Bit [2] enables/disables the voltage output mode. A logic high at STROBE enables Flash mode. A logic high on the ENVM input forces the LM3554 into Voltage Output mode. On startup, when VOUT is less than VIN the internal synchronous PFET turns on as a current source and delivers typically 350mA to the output capacitor. During this time all current sources (LED1, LED2, and LEDI) are off. When the voltage across the output capacitor reaches 2.2V, the current sources can turn on. At turn-on the current sources step through each FLASH or TORCH level until the target LED current is reached (16 s/step). This gives the device a controlled turn-on and limits inrush current from the VIN supply. PASS MODE Once the Output voltage charges up to VIN - 150mV the LM3554 will decide if the part operates in Pass Mode or Boost mode. If the voltage difference between VOUT and VLED is less than 300mV, the device will transition in Boost Mode. If the difference between VOUT and VLED is greater than 300mV, the device will operate in Pass Mode. In Pass Mode the boost converter stops switching, and the synchronous PFET turns fully on bringing VOUT up to VIN - IINxRPMOS (RPMOS = 150m). In Pass Mode the inductor current is not limited by the peak current limit. In this situation the output current must be limited to 2.5A. LIGHT LOAD DISABLE Configuration Register 1 bit [0] = 1 disables the light load comparator. With this bit set to 0 (default) the light load comparator is enabled. Light Load mode only applies when the LM3554 is active in Voltage Output mode. In LED mode the Light Load Comparator is always disabled. When the light load comparator is disabled the LM3554 will operate at a constant frequency down to ILOAD = 0. Disabling light load can be useful when a more predictable switching frequency across the entire load current range is desired. VOLTAGE OUTPUT MODE Bit 2 (VM) of the Torch Brightness Register, bit 2 (VM) of the Flash Brightness Register, or the ENVM input enables or disables the Voltage Output mode. In Voltage Output mode the device operates as a simple boost converter with two selectable voltage levels (4.5V and 5V). Write a (1) to bit 1 (OV) of Configuration Register 1 to set VOUT to 5V. Write a (0) to this bit to set VOUT to 4.5V. In Voltage Output mode the LED current sources can continue to operate; however, the difference between VOUT and VLED will be dropped across the current sources. (See Maximum Output Power section.) In Voltage Output mode when VIN is greater than VOUT the LM3554 operates in Pass Mode (see PASS MODE section). At light loads the LM3554 switches over to a pulsed frequency mode operation (light load comparator enabled). In this mode the device will only switch as necessary to maintain VOUT within regulation. This mode provides a better efficiency due to the reduction in switching losses which become a larger portion of the total power loss at light loads. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 17 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com OVER-VOLTAGE PROTECTION The output voltage is limited to typically 5.6V (5.7V max). In situations such as the current source open, the LM3554 will raise the output voltage in order to try and keep the LED current at its target value. When VOUT reaches 5.6V the over-voltage comparator will trip and turn off both the internal NFET and PFET. When VOUT falls below 5.4V (typical), the LM3554 will begin switching again. CURRENT LIMIT The LM3554 features 4 selectable current limits: 1A, 1.5A, 2A, and 2.5A. These are selectable through the I2Ccompatible interface via bits 5 (CL0) and 6 (CL1) of the Flash Duration Register. When the current limit is reached, the LM3554 stops switching for the remainder of the switching cycle. Since the current limit is sensed in the NMOS switch there is no mechanism to limit the current when the device operates in Pass Mode. In situations where there could potentially be large load currents at OUT, and the LM3554 is operating in Pass mode, the load current must be limited to 2.5A. In Boost mode or Pass mode if VOUT falls below approximately 2.3V, the part stops switching, and the PFET operates as a current source limiting the current to typically 350mA. This prevents damage to the LM3554 and excessive current draw from the battery during output short circuit conditions. MAXIMUM LOAD CURRENT (VOLTAGE MODE) Assuming the power dissipation in the LM3554 and the ambient temperature are such that the device will not hit thermal shutdown, the maximum load current as a function of IPEAK is: I LOAD = (I PEAK - 'IL) x K x VIN VOUT (1) Where is efficiency and is found in the efficiency curves in the Typical Performance Characteristics and 'IL = VIN x (VOUT - VIN ) 2 x fSW x L x VOUT (2) Maximum Output Current (A) Figure 51 shows the theoretical maximum Output current vs theoretical Efficiency at different input and output voltages using the previous two equations for IL and ILOAD with a peak current of 2.5A. This plot represents the theoretical maximum output current (for the LM3554 in Voltage Output mode) that the device can deliver just before hitting current limit. 2.3 2.2 2.1 2 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0.6 0.6 Maximum Output Current vs Efficiency (I PEAK = 2.5A) VIN = 3.6V, VOUT = 4V VIN = 3V, VOUT = 4V VIN = 3.6V, VOUT = 5V VIN = 2.5V, VOUT = 4V VIN = 3V, VOUT = 5V VIN = 2.5V, VOUT = 5V 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 Efficiency (POUT / PIN ) Figure 51. LM3554 Maximum Output Current 18 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Maximum Output Power Output power is limited by three things: the peak current limit, the ambient temperature, and the maximum power dissipation in the package. If the LM3554's die temperature is below the absolute maximum rating of +125C, the maximum output power can be over 6W. However, any appreciable output current will cause the internal power dissipation to increase and therefore increase the die temperature. This can be additionally compounded if the LED current sources are operating while the device is in Voltage Output mode since the difference between VOUT and VLED is dropped across the current sources. Any circuit configuration must ensure that the die temperature remains below +125C taking into account the ambient temperature derating. Maximum Output Power (Voltage Output Mode) In Voltage Output mode the total power dissipated in the LM3554 can be approximated as: PDISS = PN + PP + PLED1 + PLED2 + PIND (3) PN is the power lost in the NFET, PP is the PFET power loss, PLED1, PLED2, and PIND are the losses across the current sinks. An approximate calculation of these losses gives: PDISS = (VOUT - VIN ) x VOUT* (c) VIN2 x ILOAD2 x R NFET + VOUT* (c) VIN x ILOAD2 x R PFET + (VOUT - VLED ) x ILED + (VOUT - VIND) x I IND ILOAD = IOUT + ILED + I IND I LED = ILED1 + I LED2 (4) The above formulas consider the average current through the NFET and PFET. The actual power losses will be higher due to the RMS currents and the quiescent power into IN. These, however, can give a decent approximation. Maximum Output Power (Led Boost Mode) In LED mode with VOUT > VIN the LM3554's boost converter will switch and make VOUT = VLED + 0.3V. In this situation the total power dissipated in the LM3554 is approximated as: PDISS = (VLED + 0.3V - VIN ) x VLED + 0.3V)* (c) VIN 2 x ILOAD2 x R NFET + VLED + 0.3V* (c) VIN x ILOAD2 x R PFET + 0.3V x I LED + (VLED + 0.3V - VIND ) x I IND ILOAD = ILED + I IND I LED = ILED1 + I LED2 (5) Maximum Output Power (Led Pass Mode) In LED mode with VIN - ILOAD x RPFET > VLED + 0.3V, the LM3554 operates in Pass Mode. In this case. the NFET is off, and the PFET is fully on. The difference between VIN - ILOADxRPMOS and VLED will be dropped across the current sources. In this situation the total power dissipated in the LM3554 is approximated as: PDISS = [ I LOAD2 x R PFET + (VIN - R PFET x I LOAD - VLED ) x I LED + (VIN - R PFET x I LOAD - VIND) x IIND ] I LOAD = I LED + IIND I LED = I LED1 + I LED2 (6) Once the total power dissipated in the LM3554 is calculated the ambient temperature and the thermal resistance of the 16-bump micro SMD (TMD16) are used to calculate the total die temperature (or junction temperature TJ). Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 19 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com As an example, assume the LM3554 is operating at VIN = 3.6V and configured for Voltage Output mode with VOUT = 5V and IOUT = 0.7A. The LED currents are then programmed in Torch mode with 150mA each at VLED = 3.6V. Additionally, the indicator LED has 10mA at VIND = 3.6V. Using Equation 5 and Equation 6 above, the approximate total power dissipated in the device is: PDISS = 139 mW + 357 mW + 420 mW + 14 mW = 930 mW (7) The die temperature approximation will be: TJ = 0. 93 W x 60 C + 25 C = 80.8 C. W (8) In this case the device can operate at these conditions. If then the ambient temperature is increased to +85C, the die temperature would be +140.8C; thus, the die temperature would be above the absolute maximum ratings, and the load current would need to be scaled back. This example demonstrates the steps required to estimate the amount of current derating based upon operating mode, circuit parameters, and the device's junction-to-ambient thermal resistance. In this example a thermal resistance of 60C/W was used (JESD51-7 standard). Since thermal resistance from junction-to-ambient is largely PCB layout dependent, the actual number used will likely be different and must be taken into account when performing these calculations. Flash Mode In Flash mode the LED current sources (LED1 and LED2) each provide 16 different current levels from typically 34mA to approximately 600mA. The Flash currents are set by writing to bits [6:3] of the Flash Brightness Resister. Flash mode is activated by either writing a (1, 1) to bits [1:0] of the Torch Brightness Register, writing a (1,1) to bit [1:0] of the Flash Brightness Register, or by pulling the STROBE pin high. Once the Flash sequence is activated, both current sinks (LED1 and LED2) will ramp up to the programmed Flash current by stepping through all Flash levels (16s/step) until the programmed current is reached. Flash Termination (Strobe-Initiated Flash) Bit [7] of the Flash Brightness Register (STR bit) determines how the Flash pulse terminates with STROBEinitated flash pulses. With the STR bit = 1 the Flash current pulse will only terminate by reaching the end of the Flash Timeout period. With STR = 0, Flash mode can be terminated by pulling STROBE low, or by allowing the Flash Timeout period to elapse. If STR = 0 and STROBE is toggled before the end of the Flash Timeout period, the Timeout period resets on the rising edge of STROBE. See LM3554 TIMING DIAGRAMS regarding the Flash pulse termination for the different STR bit settings. After the Flash pulse terminates, either by a flash timeout, or pulling STROBE low, LED1 and LED2 turn completely off. This happens even when Torch is enabled via the I2C-compatible interface, and the Flash pulse is turned on by toggling STROBE. After a Flash event ends the EN1, EN0 bits (bits [1:0] of the Torch Brightness Register, or Flash Brightness Register) are automatically re-written with (0, 0). Flash Termination (I2C-Initiated FLASH) For I2C initated flash pulses, the flash LED current can be terminated by either waiting for the timeout duration to expire or by writing a (0, 0) to bits [1:0] of the Torch Brightness Register, or Flash Brightness Register. If the timeout duration is allowed to elapse, the flash enable bits of the Torch Brightness and Flash Brightness Registers are automatically reset to 0. Flash Timeout The Flash Timeout period sets the duration of the flash current pulse. Bits [4:0] of the Flash Duration Register programs the 32 different Flash Timeout levels in steps of 32ms giving a Flash Timeout range of 32ms to 1024ms (see Table 5). Torch Mode In Torch mode the current sources LED1 and LED2 each provide 8 different current levels (see Table 3). The Torch currents are adjusted by writing to bits [5:3] of the Torch Brightness Register. Torch mode is activated by setting Torch Brightness Register bits [1:0] to (1, 0) or Flash Brightness bits [1:0] to (1, 0). Once the Torch mode is enabled the current sources will ramp up to the programmed Torch current level by stepping through all of the Torch currents at 16s/step until the programmed Torch current level is reached. 20 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 TX1/Torch The TX1/TORCH/GPIO1 input has a triple function. With Configuration Register 1 Bit [7] = 0 (default), TX1/TORCH/GPIO1 is a Power Amplifier Synchronization input (TX1 mode). This is designed to reduce the current pulled from the battery during an RF power amplifier transmit event. When the LM3554 is engaged in a Flash event, and the TX1 pin is pulled high, both LED1 and LED2 are forced into Torch mode at the programmed Torch current setting. If the TX1 pin is then pulled low before the Flash pulse terminates the LED current will ramp back to the previous Flash current level. At the end of the Flash timeout whether the TX1 pin is high or low, the LED current will turn off. With the Configuration Register Bit [7] = 1, TX1/TORCH/GPIO1 is configured as a hardware Torch mode enable (TORCH). In this mode a high at TORCH turns on the LED current sources in Torch mode. STROBE (or I2initiated flash) will take precedence over the TORCH mode input. Figure 61 details the functionality of the hardware TORCH mode. Additionally, when a flash pulse is initiated during hardware TORCH mode, the hardware torch mode bit is reset at the end of the flash pulse. In order to re-enter hardware Torch mode, bit [7] of Configuration Register 1 would have to be re-written with a 1. The TX1/TORCH/GPIO1 input can also be configured as a GPIO input/output. for details on this, refer to the GPIO Register section of the datasheet. ENVM/TX2/GPIO2 The ENVM/TX2/GPIO2/INT pin has four functions. In ENVM mode (Configuration Register 1 bit [5] = 0), the ENVM/TX2/GPIO2/INT pin is an active high logic input that forces the LM3554 into Voltage Output Mode. In TX2 mode (Configuration Register 1 bit [5] = 1), the ENVM/TX2/GPIO2/INT pin is a Power Amplifier Synchronization input that forces the LM3554 from Flash mode into Torch mode. In GPIO2 mode (GPIO Register Bit [3] = 1) the ENVM/TX2/GPIO2/INT pin is configured as a general purpose logic input/output and controlled via bits[3:5] of the GPIO Register. In INT mode the ENVM/TX2/GPIO2/INT pin is a hardware interrupt output which pulls low when the LM3554 is in NTC mode, and the voltage at LEDI/NTC falls below VTRIP. In TX2 mode, when Configuration Register 1 bit [6] = 0 the ENVM/TX2/GPIO2 pin is an active low transmit interrupt input. Under this condition, when the LM3554 is engaged in a Flash event, and ENVM/TX2/GPIO2 is pulled low, both LED1 and LED2 are forced into either Torch mode or LED shutdown depending on the logic state of Configuration Register 2 bit [0]. In TX2 mode with Configuration Register 1 bit [6] = 1, the ENVM/TX2/GPIO2 pin is an active high transmit interrupt. Under this condition when the LM3554 is engaged in a Flash event, and the TX2 pin is driven high, both LED1 and LED2 are forced into Torch mode or LED shutdown, depending on the logic state of Configuration Register 2 bit [0]. After a TX2 event, if the ENVM/TX2/GPIO2 pin is disengaged, and the TX2 Shutdown bit is set to force Torch mode, the LED current will ramp back to the previous Flash current level. If the TX2 shutdown bit is programmed to force LED shutdown upon a TX2 event the Flags Register must be read to resume normal LED operation. Table 6, Figure 57, and Figure 58 detail the Functionality of the ENVM/TX2 input. ENVM/TX2/GPIO2/INT as an Interrupt Output In GPIO2 mode the ENVM/TX2/GPIO2 pin can be made to reflect the inverse of the LED Thermal Fault flag (bit[5] in the Flags Register). Configure the LM3554 for this feature by: set GPIO Register Bit [6] = 1 (NTC External Flag) set GPIO Register Bit [3] = 1 (GPIO2 mode) set GPIO Register Bit [4] = 1 (GPIO2 is an output) set Configuration Register 1 Bit [3] = 1 (NTC mode) When the voltage at the LEDI/NTC pin falls below VTRIP (1.05V typical), the LED Thermal Fault Flag (bit [5] in the Flags Register) is set, and the ENVM/TX2/GPIO2/INT pin is forced low. In this mode the interrupt can only be reset to the open-drain state by reading back the Flags register. INDICATOR LED/THERMISTOR (LEDI/NTC) The LEDI/NTC pin serves a dual function, either as an LED indicator driver or as a threshold detector for a negative temperature coefficient (NTC) thermistor. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 21 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Led Indicator Mode (LEDI) LEDI/NTC is configured as an LED indicator driver by setting Configuration Register 1 bit [3] = (0) and Torch Brightness Register bits [1:0] = (0, 1), or Flash Brightness Register bits [1:0] = (0, 1). In Indicator mode there are 4 different current levels available (2.3mA, 4.6mA, 6.9mA, 8.2mA). Bits [7:6] of the Torch Brightness Register set the 4 different indicator current levels. The LEDI current source has a 1V typical headroom voltage. Thermal Comparator Mode (NTC) Writing a (1) to Configuration Register 1 bit [3] disables the indicator current source and configures the LEDI/NTC pin as a detector for an NTC thermistor. In this mode LEDI/NTC becomes the negative input of an internal comparator with the positive input internally connected to a reference (VTRIP = 1.05V typical). Additionally, Configuration Register 2 bit [1] determines the action the device takes if the voltage at LEDI/NTC falls below VTRIP (while the device is in NTC mode). With Configuration register 2 bit [1] = 0, the LM3554 will be forced into Torch mode when the voltage at LEDI/NTC falls below VTRIP. With Configuration Register 2 bit [1] = 1 the device will shut down the current sources when VLEDI/NTC falls below VTRIP. When the LM3554 is forced from Flash into Torch (by VLEDI/NTC falling below VTRIP), normal LED operation (during the same Flash pulse) can only be restarted by reading from the Flags Register (0xD0) and ensuring the voltage at VLEDI/NTC is above VTRIP. When VLEDI/NTC falls below VTRIP, and the Flags register is cleared, the LM3554 will go through a 250s deglitch time before the flash current falls to either torch mode or goes into shutdown. Alternative External Torch (AET Mode) Configuration Register 2 bit [2] programs the LM3554 for Alternative External Torch mode. With this bit set to (0) (default) TX1/TORCH is a transmit interrupt that forces Torch mode only during a Flash event. For example, if TX1/TORCH goes high during a Flash event then the LEDs will be forced into Torch mode only for the duration of the timeout counter. At the end of the timeout counter the LEDs will turn off. With Configuration Register 2 bit [2] set to (1) the operation of TX1/TORCH becomes dependent on its occurrence relative to STROBE. In this mode if TX1/TORCH goes high first, then STROBE goes high, the LEDs are forced into Torch mode with no timeout. In this mode if TX1/TORCH goes high after STROBE has gone high then the TX1/TORCH pin operates as a normal TX interrupt, and the LEDs will turn off at the end of the timeout duration. (See LM3554 TIMING DIAGRAMS, Figure 59, and Figure 60.) INPUT VOLTAGE MONITOR The LM3554 has an internal comparator that monitors the voltage at IN and can force the LED current into Torch mode or into shutdown if VIN falls below the programmable VIN Monitor Threshold. Bit 0 in the VIN Monitor register (0x80) enables or disables this feature. When enabled, Bits 1 and 2 program the 4 adjustable thresholds of 3.1V, 3.2V, 3.3V, and 3.4V. Bit 3 in Configuration Register 2 (0xF0) selects whether an under-voltage event forces Torch mode or forces the LEDs off. See Figure 70/Table 8 and Figure 72/Table 10 for additional information. There is a set 100mV hysteresis for the input voltage monitor. When the input voltage monitor is active, and VIN falls below the programmed VIN Monitor Threshold, the LEDs will either turn off or their current will get reduced to the programmed Torch current setting. To reset the LED current to its previous level, two things must occur. First, VIN must go at least 100mV above the UVLO threshold and secondly, the Flags register must be read back. 22 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 LM3554 TIMING DIAGRAMS I2C Torch Command Default State Flash Brightness Register bit 7 (STR) = 0 Configuration Register 1 bit 7 (TX1/TORCH) = 0 Configuration Register 1 bit 6 (TX2 Polarity) = 1 Configuration Register bit 5 (ENVM/TX2) = 0 Configuration Register 2 bit 2 (AET) = 0 STROBE I FLASH I TORCH I LED Timeout Duration Figure 52. Normal Torch to Flash Operation (Default, Power On or RESET state of LM3554) TX1/TORCH STROBE Default State (TX event during a STROBE event) I FLASH I TORCH I LED Timeout Duration Figure 53. TX1 Event During a Flash Event (Default State,TX1/TORCH is an Active High TX Input) TX1/TORCH STROBE I LED Default State (TX1 event before and after STROBE event) I TORCH Timeout Duration Figure 54. TX1 Event Before and After Flash Event (Default State, TX1/TORCH is an Active High TX Input) Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 23 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com I2C Torch Command Default State STROBE goes high and the LEDs turn on into Flash mode. LEDs will turn off at the end of timeout duration or when STROBE goes low. Everytime STROBE goes high the timeout resets. STROBE I FLASH I TORCH ILED Timeout Duration Start of Timeout Counter Timeout Counter Reset Figure 55. STROBE Input is Level Sensitive (Default State, STR bit = 0) I2C Torch Command STROBE Flash Brightness Register bit 7 (STR) = 1 STROBE goes high and the LEDs turn on into Flash mode. LEDs will stay on for the timeout duration even if STROBE goes low before. IFLASH I TORCH I LED Timeout Duration Figure 56. STROBE Input is Edge Sensitive (STR bit = 1) I2C Torch Command ENVM/TX2 ENVM/TX2 as a transmit interrupt Configuration Register 1 bit 5 (ENVM/TX2) = 1 (ENVM/TX2 operates as a transmit interrupt) STROBE IFLASH ITORCH ILED Timeout Duration Figure 57. ENVM/TX2 Pin is Configured as an Active High TX Input 24 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 I2C Torch Command Configuration Register 1 bit 5 (ENVM/TX2) = 1 Configuration Register 1 bit 6 (ENVM/TX2) = 0 (ENVM/TX2 is configured as an active low transmit interrupt) ENVM/TX2 STROBE IFLASH ITORCH ILED Timeout Duration Figure 58. ENVM/TX2 Pin is Configured as an Active Low TX Input TX1/TORCH Configuration Register 2 bit [2] = 1 (AET) (TX1/TORCH pin goes high first. When STROBE pin goes high, LEDs will turn on into Torch. Timeout counter and flash pulse will not start until TX1/TORCH goes low) STROBE I FLASH ITORCH ILED Timeout Duration Figure 59. Alternative External Torch Mode (TX1/TORCH Turns on Before STROBE) Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 25 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com TX1/TORCH Configuration Register 2 bit [2] = 1 (AET) (STROBE goes high before TX1) STROBE IFLASH ITORCH I LED Timeout Duration Figure 60. Alternative External Torch Mode (STROBE Goes High Before TX1/TORCH, Same as Default with SEM = 0) TX1/TORCH STROBE Configuration Register 1 bit 7 (TX1/TORCH) = 1 (TX1/TORCH pin is a hardware torch input) IFLASH ITORCH ILED Timeout Duration Figure 61. TX1/TORCH Configured as a Hardware Torch input Flags Register And Fault Indicators The Flags Register (0xD0) contains the Interrupt and Fault indicators. Five fault flags are available in the LM3554. These include a Thermal Shutdown, an LED Failure Flag (LEDF) , a Timeout indicator Flag (TO), a LED Thermal Flag (NTC), and a VIN Monitor Flag. Additionally, two interrupt flag bits TX1 interrupt and TX2 interrupt indicate a change of state of the TX1/TORCH pin (TX1 mode) and ENVM/TX2 pin (TX2 mode). Reading back a "1" indicates the TX lines have changed state since the last read of the Flags Register. A read of the Flags Register resets these bits. Thermal Shutdown When the LM3554's die temperature reaches +150C the boost converter shuts down, and the NFET and PFET turn off. Additionally, all three current sources (LED1, LED2, and LEDI) turn off. When the thermal shutdown threshold is tripped a (1) gets written to bit [1] of the Flag Register (Thermal Shutdown bit). The LM3554 will start up again when the die temperature falls to below +135C. During heavy load conditions when the internal power dissipation in the device causes thermal shutdown, the part will turn off and start up again after the die temperature cools. This will result in a pulsed on/off operation. The OVT bit however will only get written once. To reset the OVT bit pull HWEN low, power down the LM3554, or read the Flags Register. 26 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 LED Fault The LED Fault flag (bit 2 of the Flags Register) reads back a (1) if the part is active in Flash or Torch mode and either LED1 or LED2 experience an open or short condition. An LED open condition is signaled if the OVP threshold is crossed at OUT while the device is in Flash or Torch mode. An LED short condition is signaled if the voltage at LED1 or LED2 goes below 500mV while the device is in Torch or Flash mode. There is a delay of 250s before the LEDF flag is valid on a LED short. This is the time from when VLED falls below the LED short threshold of 500mV (typical) to when the fault flag is valid. There is a delay of 2s from when the LEDF flag is valid on an LED open. This delay is the time between when the OVP threshold is triggered and when the fault flag is valid. The LEDF flag can only be reset to (0) by pulling HWEN low, removing power to the LM3554, or reading the Flags Register. Flash Timeout The TO flag (bit [0] of the Flags Register) reads back a (1) if the LM3554 is active in Flash mode and the Timeout period expires before the Flash pulse is terminated. The flash pulse can be terminated before the Timeout period expires by pulling the STROBE pin low (with STR bit '0'), or by writing a `0' to bit 0 or 1 of the Torch Brightness Register or the Flash Brightness Register. The TO flag is reset to (0) by pulling HWEN low, removing power to the LM3554, reading the Flags Register, or when the next Flash pulse is triggered. LED Thermal Fault The NTC flag (bit [5] of the Flags Register) reads back a (1) if the LM3554 is active in Flash or Torch mode, the device is in NTC mode, and the voltage at LEDI/NTC has fallen below VTRIP (1.05V typical). When this has happened and the LM3554 has been forced into Torch or LED shutdown (depending on the state of Configuration Register 2 bit [1], the Flags Register must be read in order to place the device back in normal operation. (See Thermal Comparator Mode (NTC) section for more details.) Input Voltage Monitor Fault The VIN Monitor Flag (bit [6] of the Flag Register) reads back a '1' when the Input Voltage Monitor is enabled and VIN falls below the programmed VIN Monitor threshold. This flag must be read back in order to resume normal operation after the LED current has been forced to Torch mode or turned off due to a VIN Monitor event. TX1 and TX2 Interrupt Flags The TX1 and TX2 interrupt flags (bits [3] and [4]) indicate a TX event on the TX1/TORCH and ENVM/TX2 pins. Bit 3 will read back a (1) if TX1/TORCH is in TX1 mode and the pin has changed from low to high since the last read of the Flags Register. Bit 4 will read back a (1) if ENVM/TX2 is in TX2 mode and the pin has had a TX event since the last read of the Flags Register. A read of the Flags Register automatically resets these bits. The ENVM/TX2/GPIO2 pin, when configured in TX2 mode, has a TX event that can be either a high-to-low transition or a low-to-high transition depending on the setting of the TX2 polarity bit (see Table 7). I2C-Compatible Interface Start And Stop Conditions The LM3554 is controlled via an I2C-compatible interface. START and STOP conditions classify the beginning and end of the I2C session. A START condition is defined as SDA transitioning from HIGH to LOW while SCL is HIGH. A STOP condition is defined as SDA transitioning from LOW to HIGH while SCL is HIGH. The I2C master always generates the START and STOP conditions. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 27 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com SDA SCL S P Start Condition Stop Condition Figure 62. Start and Stop Sequences The I2C bus is considered busy after a START condition and free after a STOP condition. During data transmission the I2C master can generate repeated START conditions. A START and a repeated START condition are equivalent function-wise. The data on SDA must be stable during the HIGH period of the clock signal (SCL). In other words, the state of SDA can only be changed when SCL is LOW. Figure 3 and Figure 63 show the SDA and SCL signal timing for the I2C-Compatible Bus. See Electrical Characteristics for timing values. t1 SCL t5 t4 SDA_IN t2 SDA_OUT t3 Figure 63. I2C-Compatible Timing I2C-Compatible Chip Address The device address for the LM3554 is 1010011 (53). After the START condition, the I2C master sends the 7-bit address followed by an eighth bit, read or write (R/W). R/W = 0 indicates a WRITE and R/W = 1 indicates a READ. The second byte following the device address selects the register address to which the data will be written. The third byte contains the data for the selected register. MSB 1 Bit 7 LSB 0 Bit 6 1 Bit 5 0 Bit 4 0 Bit 3 1 Bit 2 1 Bit 1 R/W Bit 0 2 I C Slave Address (chip address) Figure 64. Device Address Transferring Data Every byte on the SDA line must be eight bits long, with the most significant bit (MSB) transferred first. Each byte of data must be followed by an acknowledge bit (ACK). The acknowledge related clock pulse (9th clock pulse) is generated by the master. The master releases SDA (HIGH) during the 9th clock pulse (write mode). The LM3554 pulls down SDA during the 9th clock pulse, signifying an acknowledge. An acknowledge is generated after each byte has been received. 28 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Register Descriptions Table 2. LM3554 Internal Registers Register Name Internal Hex Address Power On or Reset Value Torch Brightness 0xA0 0x50 Flash Brightness 0xB0 0x68 Flash Duration 0xC0 0x4F Flag Register 0xD0 0x40 Configuration Register 1 0xE0 0x42 Configuration Register 2 0xF0 0xF0 GPIO Register 0x20 0x80 VIN Monitor Register 0x80 0xF0 TORCH Brightness Register Bits [2:0] of the Torch Brightness Register, or bits [2:0] of the Flash Brightness Register place the device in shutdown or control the on/off state of Torch, Flash, the Indicator LED and the Voltage output mode (see Table 3). Writing to Torch Brightness Register bits [2:0] automatically updates the Flash Brightness Register bits [2:0]; writing to bits [2:0] of the Flash Brightness Register automatically updates bits [2:0] of the Torch Brightness Register. Bits [5:3] set the current level in Torch mode (see Table 3). Bits [7:6] set the LED Indicator current level (see Table 3). Torch Brightness Register Register Address 0xA0 MSB IND1 Bit 7 IND0 Bit 6 TC2 Bit 5 TC1 Bit 4 TC0 Bit 3 LSB VM Bit 2 EN1 Bit 1 EN0 Bit 0 Figure 65. Torch Brightness Register Description Table 3. Torch Brightness Register Bit Settings Bit 7 (IND1) Bit 6 (IND0) Indicator Current Select Bits 00 = 2.3mA 01 = 4.6mA (default state) 10 = 6.9mA 11 = 8.2mA Bit 5 (TC2) Bit 4 (TC1) Bit 3 (TC0) Torch Current Select Bits 000 = 17mA (34mA total) 001 = 35.5mA (71mA total) 010 = 54mA (108mA total) default state 011 = 73mA (146mA total) 100 = 90mA (180mA total) 101 = 109mA (218mA total) 110 = 128mA (256mA total) 111 = 147.5mA (295mA total) Bit 2 (VM) Bit 1 (EN1) Bit 0 (EN0) Enable Bits 000 = Shutdown (default) 001 = Indicator Mode 010 = Torch Mode 011 = Flash Mode (bits reset at timeout) 100 = Voltage Output Mode 101 = Voltage Output + Indicator Mode 110 = Voltage Output + Torch Mode 111 = Voltage Output + Flash Mode (bits [1:0] are reset at end of timeout) Flash Brightness Register Bits [2:0] of the Torch Brightness Register, or bits [2:0] of the Flash Brightness Register place the device in shutdown or control the on/off state of Torch, Flash, the Indicator LED and the Voltage output mode. Writing to the Flash Brightness Register bits [2:0] automatically updates the Torch Brightness Register bits [2:0]. Bits [6:3] set the current level in Flash mode (see Table 4). Bit [7] sets the STROBE Termination select bit (STR) (see Table 4). Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 29 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Flash Brightness Register Register Address 0xB0 MSB STR Bit 7 FC3 Bit 6 FC1 Bit 4 FC2 Bit 5 FC0 Bit 3 LSB VM Bit 2 EN1 Bit 1 EN0 Bit 0 Figure 66. Flash Brightness Register Description Table 4. Flash Brightness Register Bit Settings Bit 7 (STR) Bit 6 (FC3) STROBE Edge or Level Select 0 = (Level Sensitive) When STROBE goes high, Flash current will turn on and remain on for the duration the STROBE pin is held high or when Flash Timeout occurs, whichever comes first.(default) 1 = (Edge Triggered) When STROBE goes high , Flash current will turn on and remain on for the duration of the Flash Timeout. Bit 5 (FC2) Bit 4 (FC1) Bit 3 (FC0) Bit 2 (VM) Flash Current Select Bits 0000 = 35.5mA (71mA total) 0001 = 73mA (146mA total) 0010 = 109mA (218mA total) 0011 = 147.5mA (295mA total) 0100 = 182.5mA (365mA total) 0101 = 220.5mA (441mA total) 0110 = 259mA (518mA total) 111 = 298mA (596mA total) 1000 =326mA (652mA total) 1001 = 364.5mA (729mA total) 1010 = 402.5mA (805mA total) 1011 = 440.5mA (881mA total) 1100 = 480mA (960mA total) 1101 = 518.5mA (1037mA total) Default 1110 = 556.5mA (1113mA total) 1111 = 595.5mA (1191mA total) Bit 1 (EN1) Bit 0 (EN0) Enable Bits 000 = Shutdown (default) 001 = Indicator Mode 010 = Torch Mode 011 = Flash Mode (bits reset at timeout) 100 = Voltage Output Mode 101 = Voltage Output + Indicator Mode 110 = Voltage Output + Torch Mode 111 = Voltage Output + Flash Mode (bits [1:0] are reset at end of timeout) FLASH DURATION REGISTER Bits [4:0] of the Flash Duration Register set the Flash Timeout duration. Bits [6:5] set the switch current limit. Bit [7] defaults as a '1' and is not used (see Table 5). Flash Duration Register Register Address 0xC0 MSB N/A Bit 7 CL1 Bit 6 CL0 Bit 5 T4 Bit 4 T3 Bit 3 LSB T2 Bit 2 T1 Bit 1 T0 Bit 0 Figure 67. Flash Duration Register Description 30 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Table 5. Flash Duration Register Bit Settings Bit 7 (Not used) Reads Back '0' Bit 6 (CL1) Bit 5 (CL0) Current Limit Select Bits 00 = 1A Peak Current Limit 01 = 1.5A Peak Current Limit 10 = 2A Peak Current Limi(default) 11 = 2.5A Peak Current Limit Bit 4 (T4) Bit 3 (T3) Bit 2 (T2) Bit 1 (T1) Bit 0 (T0) Flash Timeout Select Bits 00000 = 32ms timeout 00001 = 64ms timeout 00010 = 96ms timeout 00011 = 128ms timeout 00100 = 160ms timeout 00101 = 192ms timeout 00110 = 224ms timeout 00111 = 256ms timeout 01000 = 288ms timeout 01001 = 320ms timeout 01010 = 352ms timeout 01011 = 384ms timeout 01100 = 416ms timeout 01101 = 448ms timeout 01110 = 480ms timeout 01111 = 512ms timeout (default) 10000 = 544ms timeout 10001 = 576ms timeout 10010 = 608ms timeout 10011 = 640ms timeout 10100 = 672ms timeout 10101 = 704ms timeout 10110 = 736ms timeout 10111 = 768ms time-out 11000 = 800ms timeout 11001 = 832ms timeout 11010 = 864ms timeout 11011 = 896ms timeout 11100 = 928ms timeout 11101 = 960ms timeout 11110 = 992ms timeout 11111 = 1024ms timeout Flags Register The Flags Register holds the status of the flag bits indicating LED Failure, Over-Temperature, the Flash Timeout expiring, VIN Monitor Fault, LED over temperature (NTC), and a TX interrupt. (See Figure 67 and Table 6.) Flags Register Register Address 0xD0 MSB VIN Monitor Fault Bit 7 N/A Bit 6 LED Thermal Fault Bit 5 TX2 Interrupt Bit 4 TX1 Interrupt Bit 3 LSB LED Fault Bit 2 Thermal Shutdown Bit 1 Flash Timeout Bit 0 Figure 68. Flags Register Description Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 31 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Table 6. Flags Register Bit Settings Bit 7 (VIN Monitor Fault Fault) Bit 6 (Unused) Bit 5 (LED Thermal Fault) Bit 4 (TX2 Interrupt) Bit 3 (TX1 Interrupt ) Bit 2 (Led Fault) 0=No Fault at VIN (default) Not Used (Reads Back '1') 0=LEDI/NTC pin is above VTRIP (default) 0=ENVM/TX2 has not changed state (default) 0=TX1/TORCH has not changed state (default) 0 = Proper LED Operation (default) 1=LEDI/NTC has fallen below VTRIP(NTC mode only) 1=ENVM/TX2 has changed state (TX2 mode only) 1=TX1/TORCH pin has changed state (TX1 mode only) 1 = LED Failed (Open or Short 1=Input Voltage Monitor is enabled and VIN has fallen below the programmed threshold Bit 1 (Thermal Shutdown) Bit 0 (Flash Timeout) 0 = Die 0 = Flash Temperature TimeOut did not below Thermal expire (default) Shutdown Limit (default) 1 = Die Temperature has crossed the Thermal Shutdown Threshold 1 = Flash TimeOut Expired Configuration Register 1 Configuration Register 1 holds the light load disable bit, the voltage mode select bit (OV), the external flash inhibit bit, the control bit for the LEDI/NTC pin, the control bit for ENVM to TX2 mode, the polarity selection bit for the TX2 input, and the control bit for the TX1/TORCH bit (see Figure 69 and Table 7). Configuration Register 1 Register Address 0xE0 MSB LSB TX1/ TORCH TX2 Polarity ENVM/TX2 HYST LEDI/NTC Ext Flash Inhibit OV Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LL Disable Bit 0 Figure 69. Configuration Register 1 Description Table 7. Configuration Register 1 Bit Settings Bit 7 (Hardware Torch Mode Enable) Bit 6 (TX2 Polarity) Bit 5 (ENVM/TX2) Bit 4 (N/A) Bit 3 (LEDI/NTC) Bit 2 (External Flash Inhibit) Bit 1 (OV, Output Voltage Select) Bit 0 (Disable Light Load ) 0= TX1/TORCH is a TX1 flash interrupt input (default) 0 = ENVM/TX2 pin is an active low Flash inhibit 0 = ENVM Mode The ENVM/TX2 pin is a logic input to enable Voltage Mode. A high on ENVM/TX2 will force Voltage Output Mode (default) Reads Back '0' 0 = LEDI/NTC pin in Indicator mode (default) 0 = STROBE Input Enabled (default) 0 = Voltage Mode output voltage is 4.5V 0 = Light load comparator is enabled. The LM3554 will go into PFM mode at light load (default). 1= TX1/TORCH pin is a hardware TORCH enable 1 = ENVM/TX2 1 = TX2 Mode pin is an active The ENVM/TX2 high Flash is a Power inhibit (default) Amplifier Synchronization input. A high on ENVM/TX2 will force the LM3554 from Flash to Torch mode. 1 = LEDI/NTC pin in Thermal Comparator Mode. Indicator current is disabled. 1 = STROBE Input Disabled 1 = Voltage Mode output voltage is 5V (default) 1 = Light load comparator is disabled. The LM3554 will not go into PFM mode at light load. 32 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 Configuration Register 2 Configuration Register 2 contains the bits to select if TX2, NTC, and the VIN monitor force Torch mode or force the Flash LEDs into shutdown. Additionally, bit [2] (AET bit) selects the Alternate External Torch mode (see Figure 70 and Table 8). Configuration Register 2 Register Address 0xF0 MSB N/A N/A N/A N/A Bit 7 Bit 6 Bit 5 Bit 4 VIN Monitor Mode Bit 3 LSB AET Mode Bit 2 NTC Shutdown Bit 1 TX2 Shutdown Bit 0 Figure 70. Configuration Register 2 Description Table 8. Configuration Register 2 Bit Settings Bit 7 (Not used) Bit 6 (Not used) Bit 5 (Not used) Bit 4 (Not used) Bit 3 (VIN Monitor Shutdown) Bit 2 (AET mode) Bit 1 (NTC Shutdown) Bit 0 (TX2 Shutdown) Reads Back '1' Reads Back '1' Reads Back '1' Reads Back '1' 0 = If IN drops below the programmed threshold and the VIN Monitor feature is enabled, the LED's are forced into Torch mode (default) 0 = Normal operation for TX1/TORCH high before STROBE (TX1 mode only) default 0 = LEDI/NTC pin going below VTRIP forces the LEDs into Torch mode (NTC mode only) default 0 = TX2 event forces the LEDs into Torch mode (TX2 mode only) default 1 = If IN drops below the programmed threshold and the VIN Monitor feature is enabled, the LED's turn off 1 = Alternative External Torch operation. TX1/TORCH high before STROBE forces Torch mode with no timeout (TX1 mode only) 1 = LEDI/NTC 1 = TX2 event pin going below forces the VTRIP forces the LEDs into LEDs into shutdown (TX2 shutdown (NTC mode only) mode only) GPIO Register The GPIO register contains the control bits which change the state of the TX1/TORCH/GPIO1 pin and the ENVM/TX2/GPIO2 pin to general purpose I/O's (GPIO's). Additionally, bit[6] of this register configures the ENVM/TX2/GPIO2 as a hardware interrupt output reflecting the NTC flag bit in the Flags Register. Figure 71 and Table 9 describe the bit description and functionality of the GPIO register. GPIO Register Register Address 0x20 MSB Not Used Bit 7 NTC External Flag Bit 6 Data Data Direction Bit 5 Bit 4 ENVM/ TX2/GPIO2 Bit 3 LSB Data Bit 2 Data Direction Bit 1 TX1/TORCH/ GPIO1 Bit 0 Figure 71. GPIO Register Description Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 33 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Table 9. GPIO Register Bit Settings Bit 7 (Not Used) Bit 6 (NTC External Flag) Reads Back '1' 0 = NTC External Flag mode is disabled (default) Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (ENVM/TX2/GP (ENVM/TX2/GP (ENVM/TX2/GP (TX1/TORCH/G (TX1/TORCH/G (TX1/TORCH/G IO2 data) IO2 data IO2 Control) PIO1 data) PIO1 data PIO1 Control) direction) direction) This bit is the 0= 0= read or write ENVM/TX2/GPI ENVM/TX2/GPI data for the O2 is a GPIO O2 is ENVM/TX2/GPI Input (default) configured O2 pin in GPIO according to mode (default the is 0) Configuration Register bit 5 (default) 1 = When ENVM/TX2/GPI O2 is configured as a GPIO output the ENVM/TX2/GPI O2 pin will pull low when the LED Thermal Fault Flag is set This bit is the read or write data for the TX1/TORCH/G PIO1 pin in GPIO mode (default is 0) 1= 1= ENVM/TX2/GPI ENVM/TX2/GPI O2 is a GPIO O2 is Output configured as a GPIO 0= TX1/TORCH/G PIO1 is a GPIO input (default) 0= TX1/TORCH/G PIO1 pin is configured as an active low reset input (default) 1= 1= TX!/TORCH/GP TX1/TORCH/G IO1 is an PIO1 pin is output configured as a GPIO VIN MONITOR REGISTER The VIN Monitor Register controls the on/off state of the VIN Monitor comparator as well as selects the 4 programmable thresholds. Figure 72 and Table 10 describe the bit settings of the VIN Monitor feature. VIN Monitor Register Register Address 0x80 MSB LSB N/A N/A N/A N/A N/A VIN Threshold VIN Threshold Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 VIN Monitor Enable Bit 0 Figure 72. VIN Monitor Register Description Table 10. VIN Monitor Register Bit Settings Bit 7 (Not used) Bit 6 (Not used) Bit 5 (Not used) Bit 4 (Not used) Bit 3 (Not used) Reads Back '1' Reads Back '1' Reads Back '1' Reads Back '1' Reads Back '0' Bit 2 (VIN Threshold) Bit 1 (VIN Threshold) 00 = 3.1V threshold (VIN falling) Default 01=3.2V threshold (VIN falling) 10 = 3.3V threshold (VIN falling) 11 = 3.4V threshold (VIN falling) Bit 0 (VIN Monitor Enable) 0 = VIN Monitoring Comparator is disabled (default) 1 = VIN Monitoring Comparator is enabled. 34 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 APPLICATIONS INFORMATION Output Capacitor Selection The LM3554 is designed to operate with a at least a 4.7F ceramic output capacitor in LED mode and a 10F output capacitor in Voltage Output Mode. When the boost converter is running the output capacitor supplies the load current during the boost converters on-time. When the NMOS switch turns off the inductor energy is discharged through the internal PMOS switch supplying power to the load and restoring charge to the output capacitor. This causes a sag in the output voltage during the on-time and a rise in the output voltage during the off-time. The output capacitor is therefore chosen to limit the output ripple to an acceptable level depending on load current and input/output voltage differentials and also to ensure the converter remains stable. For proper LED operation the output capacitor must be at least a 4.7F ceramic (10F in Voltage Output Mode). Larger capacitors such as 10F or 22F can be used if lower output voltage ripple is desired. To estimate the output voltage ripple considering the ripple due to capacitor discharge (VQ) and the ripple due to the capacitors ESR (VESR) use the following equations: For continuous conduction mode, the output voltage ripple due to the capacitor discharge is: 'VQ = ILED x (VOUT - VIN) fSW x VOUT x COUT (9) The output voltage ripple due to the output capacitors ESR is found by: 'VESR = R ESR x (c) where 'IL = I LED x VOUT* VIN + 'I L VIN x (VOUT - VIN ) 2 x f SW x L x VOUT (10) In ceramic capacitors the ESR is very low so assume that 80% of the output voltage ripple is due to capacitor discharge and 20% from ESR. Table 11 lists different manufacturers for various output capacitors and their case sizes suitable for use with the LM3554. Input Capacitor Selection Choosing the correct size and type of input capacitor helps minimize the voltage ripple caused by the switching of the LM3554's boost converter and reduces noise on the devices input terminal that can feed through and disrupt internal analog signals. In the Typical Application Circuit a 4.7F ceramic input capacitor works well. It is important to place the input capacitor as close as possible to the LM3554's input (IN) terminals. This reduces the series resistance and inductance that can inject noise into the device due to the input switching currents. Table 11 lists various input capacitors that or recommended for use with the LM3554. Table 11. Recommended Input/Output Capacitors (X5R Dielectric) Manufacturer Part Number Value Case Size Voltage Rating TDK Corporation C1608JB0J475K 4.7F 0603(1.6mmx0.8mmx0.8mm) 6.3V TDK Corporation C1608JB0J106M 10F 0603(1.6mmx0.8mmx0.8mm) 6.3V TDK Corporation C2012JB1C475K 4.7F 0805(2mmx1.25mmx1.25mm) 16V TDK Corporation C2012JB1A106M 10F 0805(2mmx1.25mmx1.25mm) 10V TDK Corporation C2012JB0J226M 22F 0805(2mmx1.25mmx1.25mm) 6.3V Murata GRM188R60J475KE19 4.7F 0603(1.6mmx0.8mmx0.8mm) 6.3V Murata GRM21BR61C475KA88 4.7F 0805(2mmx1.25mmx1.25mm) 16V Murata GRM21BR61A106KE19 10F 0805(2mmx1.25mmx1.25mm) 10V Murata GRM21BR60J226ME39L 22F 0805(2mmx1.25mmx1.25mm) 6.3V Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 35 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Inductor Selection The LM3554 is designed to use a 2.2H inductor. Table 12 lists various inductors and their manufacturers that can work well with the LM3554. When the device is boosting (VOUT > VIN) the inductor will typically be the biggest area of efficiency loss in the circuit. Therefore, choosing an inductor with the lowest possible series resistance is important. Additionally, the saturation rating of the inductor should be greater than the maximum operating peak current of the LM3554. This prevents excess efficiency loss that can occur with inductors that operate in saturation and prevents over heating of the inductor and possible damage. For proper inductor operation and circuit performance ensure that the inductor saturation and the peak current limit setting of the LM3554 is greater than IPEAK can be calculated by: IPEAK = I LOAD VOUT V x (VOUT - VIN) x + 'IL where 'IL = IN K VIN 2 x f SW x L x VOUT (11) SW = 2MHz; can be found in the Typical Performance Characteristics plots. Table 12. Recommended Inductors Manufacturer L Part Number Dimensions (LxWxH) ISAT TOKO 2.2H FDSE0312-2R2M 3mmx3mmx1.2mm 2A TDK 2.2H VLS252012T-2R2M1R3 2mmx2.5mmx1.2mm 1.5A Coilcraft 2.2H LPS4018-222ML 3.9mmx3.9mmx1.7mm 2.3A NTC Thermistor Selection NTC thermistors have a temperature to resistance relationship of: E R(T) = R25C x e 1 - 1* (c)T C+ 273 298 (12) where is given in the thermistor datasheet and R25C is the thermistors value at +25C. R3 in Figure 74 is chosen so that it is equal to: R3 = RT( TRIP) (VBIAS - VTRIP ) VTRIP (13) where R(T)TRIP is the thermistors value at the temperature trip point, VBIAS is shown in Figure 74, and VTRIP = 1.05V (typical). Choosing R3 here gives a more linear response around the temperature trip voltage. For example, with VBIAS = 2.5V, a thermistor whose nominal value at +25C is 100k and a = 4500K, the trip point is chosen to be +93C. The value of R(T) at 93C is: E R3 is then: 1/4 R(T) = 100 k : x e 1 - 1 93 + 273 298 1/4 = 6.047 k : 6.047 k: x (2.5 V - 1V) = 9 .071 k: 1V (14) Figure 73 shows the linearity of the thermistor resistive divider of the previous example. 36 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 1.5 VBIAS = 2.5V, RTHERMISTOR = 100 k: @ +25C, B = 4500, R3 = 9 k: 1.4 1.3 V LEDI/NTC (V) 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 70 75 80 85 90 95 100 105 110 TEMPERATURE (C) Figure 73. Thermistor Resistive Divider Response vs Temperature Another useful equation for the thermistor resistive divider is developed by combining the equations for R3, and R(T) and solving for temperature. This gives the following relationship. E x 298 C - 273C T( C) = VTRIP x R3 E 298C x LN (VBIAS - VTRIP ) x R25 C + 1/4 (15) Using a spreadsheet such as Excel, different curves for the temperature trip point T(C) can be created vs R3, Beta, or VBIAS in order to help better choose the thermal components for practical values of thermistors, series resistors (R3), or reference voltages VBIAS. Programming bit [3] of the Configuration register with a (1) selects Thermal Comparator mode making the LEDI/NTC pin a comparator input for flash LED thermal sensing. Figure 74 shows the internal block diagram of the thermal sensing circuit which is OR'd with both the TX1 and ENVM/TX2 (TX2 mode) to force the LM3554 from Flash to Torch mode. This is intended to prevent LED overheating during flash pulses. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 37 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com Internal to LM3554 TX2 VIN Monitor TX1/TORCH Force Torch or LED Shutdown (VIN Monitor, TX2 or NTC only) VBIAS 1.05V LEDI/ NTC R3 + R(T) 0.1 PF Figure 74. Thermistor Voltage Divider and Sensing Circuit NTC Thermistor Placement The termination of the thermistor must be done directly to the cathode of the Flash LED in order to adequately couple the heat from the LED into the thermistor. Consequentally, the noisy environment generated from the switching of the LM3554's boost converter can introduce noise from GND into the thermistor sensing input. To filter out this noise it is necessary to place a 0.1F or larger ceramic capacitor close to the LEDI/NTC pin. The filter capacitor's return must also connect with a low-impedance trace, as close as possible to the PGND pin of the LM3554. Layout Recommendations The high frequency and large switching currents of the LM3554 make the choice of layout important. The following steps should be used as a reference to ensure the device is stable and maintains proper voltage and current regulation across its intended operating voltage and current range. 1. Place CIN on the top layer (same layer as the LM3554) and as close to the device as possible. The input capacitor conducts the driver currents during the low-side MOSFET turn-on and turn-off and can see current spikes over 1A in amplitude. Connecting the input capacitor through short wide traces on both the IN and GND terminals will reduce the inductive voltage spikes that occur during switching and which can corrupt the VIN line. 2. Place COUT on the top layer (same layer as the LM3554) and as close as possible to the OUT and GND terminal. The returns for both CIN and COUT should come together at one point, and as close to the GND pin as possible. Connecting COUT through short wide traces will reduce the series inductance on the OUT and GND terminals that can corrupt the VOUT and GND line and cause excessive noise in the device and surrounding circuitry. 3. Connect the inductor on the top layer close to the SW pin. There should be a low impedance connection from the inductor to SW due to the large DC inductor current, and at the same time the area occupied by the SW node should be small so as to reduce the capacitive coupling of the high dV/dt present at SW that can couple into nearby traces. 4. Avoid routing logic traces near the SW node so as to avoid any capacitively coupled voltages from SW onto any high-impedance logic lines such as TX1/TORCH/GPIO1, ENVM/TX2/GPIO2, HWEN, LEDI/NTC (NTC mode), SDA, and SCL. A good approach is to insert an inner layer GND plane underneath the SW node and 38 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 LM3554 www.ti.com SNVS549B - JUNE 2009 - REVISED MAY 2013 between any nearby routed traces. This creates a shield from the electric field generated at SW. 5. Terminate the Flash LED cathodes directly to the GND pin of the LM3554. If possible, route the LED returns with a dedicated path so as to keep the high amplitude LED currents out the GND plane. For Flash LEDs that are routed relatively far away from the LM3554, a good approach is to sandwich the forward and return current paths over the top of each other on two layers. This will help in reducing the inductance of the LED current paths. 6. The NTC Thermistor is intended to have its return path connected to the LED's cathode. This allows the thermistor resistive divider voltage (VNTC) to trip the comparators threshold as VNTC is falling. Additionally, the thermistor-to-LED cathode junction can have low thermal resistivity since both the LED and the thermistor are electrically connected at GND. The drawback is that the thermistor's return will see the switching currents from the LM3554's boost converter. Because of this, it is necessary to have a filter capacitor at the NTC pin which terminates close to the GND of the LM3554 and which can conduct the switched currents to GND. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 39 LM3554 SNVS549B - JUNE 2009 - REVISED MAY 2013 www.ti.com REVISION HISTORY Changes from Revision A (May 2013) to Revision B * 40 Page Changed layout of National Data Sheet to TI format .......................................................................................................... 39 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM3554 PACKAGE OPTION ADDENDUM www.ti.com 3-May-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (C) Top-Side Markings (3) (4) LM3554TME/NOPB ACTIVE DSBGA YFQ 16 250 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM -30 to 85 SF LM3554TMX/NOPB ACTIVE DSBGA YFQ 16 3000 Green (RoHS & no Sb/Br) SNAGCU Level-1-260C-UNLIM -30 to 85 SF (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) Multiple Top-Side Markings will be inside parentheses. Only one Top-Side Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Top-Side Marking for that device. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 1 Samples PACKAGE MATERIALS INFORMATION www.ti.com 8-May-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) LM3554TME/NOPB DSBGA YFQ 16 250 178.0 8.4 LM3554TMX/NOPB DSBGA YFQ 16 3000 178.0 8.4 Pack Materials-Page 1 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 1.85 2.01 0.76 4.0 8.0 Q1 1.85 2.01 0.76 4.0 8.0 Q1 PACKAGE MATERIALS INFORMATION www.ti.com 8-May-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM3554TME/NOPB DSBGA YFQ LM3554TMX/NOPB DSBGA YFQ 16 250 210.0 185.0 35.0 16 3000 210.0 185.0 35.0 Pack Materials-Page 2 MECHANICAL DATA YFQ0016xxx D 0.6000.075 E TMD16XXX (Rev A) D: Max = 1.685 mm, Min =1.624 mm E: Max = 1.685 mm, Min =1.624 mm 4215081/A NOTES: A. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994. B. 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