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FAN5776 Synchronous Boost and Series / Parallel 10-LED Driver Features Description Synchronous Current-Mode Boost Converter 5 LED Outputs: High-Side Current Sources The FAN5776 is a synchronous, constant-current LED driver capable of efficiently driving up to ten LEDs in a five-string, two-series LEDs per string configuration. Optimized for small form-factor applications, the 1.8 MHz switching frequency allows the use of tiny chip inductors and capacitors. Drives up to 10 LEDs at 25 mA Each in a Configuration of 5 Strings of 2 LEDs in Series Two Default Groups of 3x2-LED Channels and 2x2-LED Channels with Individual Enable and PWM Dimming Control to Support Various Lighting Applications, such as: o Backlighting of Dual-LCD Displays, LCD Display Plus Keypad Illumination Boost PFM Mode Maximizes Efficiency Under Light Loads 2.3 V to 5.5 V Input Voltage Range 1.8 MHz Switching Frequency Input Under-Voltage Lockout (UVLO) Output Over-Voltage Protection (OVP) Short-Circuit and Thermal Shutdown (TSD) Protection 12-Bump, 0.4 mm Pitch, 1.42 x 1.66 x 0.50 mm WLCSP Applications For safety, the device features integrated over-voltage, shortcircuit, and thermal shutdown protections. In addition, input under-voltage lockout protection is triggered if the battery voltage is too low. The FAN5776 is comprised of low-dropout, high-side current sources, enabling a high efficiency delivery of power from the battery to the LEDs. The LED current control is established with a series RSET resistor, which is connected between the internal voltage reference on the chip and ground. During operation, FAN5776 holds the boost regulator's voltage on COUT during the off cycle of the PWM dimming, which helps minimize audible noise. The FAN5776 is available in a very low profile, small-formfactors 1.42 x 1.66 x 0.50 mm, 12-bump WLCSP package that is "green" and RoHS compliant. Mid-and Large-Size LCD Modules Cellular Mobile Handsets, Smart Phones Smartbooks, Netbooks, MIDs Pocket PCs WLAN DC-DC Converter Modules PDA, DSC, PMP, and MP3 Players Ordering Information Part Number Temperature Range FAN5776UCX -40 to 85C (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 Package 12-Bump, Wafer-Level Chip-Scale Package (WLCSP) 1.42 x 1.66 x 0.50 mm, 0.40 mm Pitch Packing Tape and Reel www.fairchildsemi.com FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver October 2013 Q2 SW VOUT COUT L1 Q1 LED1 LED2 VIN CURRENT SOURCES MODULATOR LOGIC AND CONTROL CIN EN13 DIGITAL CONTROL OF STARTUP EN45 LED3 LED4 LED5 FB GND ISET Group 2 Group 1 RSET Figure 1. Table 1. Typical Application Block Diagram Recommended External Components Component Description Vendor L1 IL1 = 500 mA Various RSET 1% or Better Various R 20 COUT 10 F X5R or Better Murata GRM219R61A116UE82 C 4.2 CIN 2.2 F X5R or Better Murata GRM155R61A225KE95 C (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 Parameter Min. Typ. L 2.45 4.70 R 10.0 2.2 Max. Units H 0.30 200 k 20.0 F F www.fairchildsemi.com 2 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Block Diagram VIN ISET LED1 A1 A2 A3 EN13 B1 B2 B3 GND C1 C2 C3 A3 A2 A1 LED2 B3 B2 B1 LED3 C3 C2 C1 D3 D2 D1 EN45 LED5 D1 SW Figure 2. D2 D3 VOUT LED4 Top View (Bumps Face Down) Figure 3. Bottom View (Bumps Face Up) Pin Definitions Pin # Name Description A1 VIN Input voltage A2 ISET The LED current is set by tying this pin through the resistor, R SET, to GND. The resistor value sets the current for the LED strings. A3 LED1 LED string #1 output B1 EN13 Enable/PWM pin for LED1, LED2, and LED3. A logic LOW on this pin turns off the LED drivers in LED1, LED2, and LED3. The IC goes to shutdown 30 ms after both enable pins (EN13 and EN45) are set LOW. It is connected to an internal pull-down resistor of 250 k. B2 EN45 Enable/PWM pin for LED4 and LED5. A logic LOW on this pin turns off the LED drivers in LED4 and LED5. The IC goes to shutdown 30 ms after both enable pins (EN13 and EN45) are set LOW. It is connected to an internal pull-down resistor of 250 k. B3 LED2 LED string #2 output C1 GND Ground. All power and analog signals are referenced to this pin. C2 LED5 LED string #5 output C3 LED3 LED string #3 output D1 SW D2 VOUT Boost output voltage used to supply the LED current sources. This voltage is regulated to the minimum value required to ensure adequate voltage across all active LED current sources. D3 LED4 LED string #4 output Switching Node. Tie inductor L1 from VIN to this pin. (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 www.fairchildsemi.com 3 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Pin Configuration Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. Symbol Parameter Min. Max. Unit Supply Voltage -0.3 6.0 V VISET ISET Voltage -0.3 VIN + 0.3 V VEN EN13 and EN45 Pin Maximum Voltage -0.3 6.0 V VOVP VOUT, SW, and LEDx Drive Pins Maximum Voltage -0.3 11.0 V ESD Electrostatic Discharge Protection Human Body Model per JESD22-A114 Level Charged Device Model per JESD22-C101 VIN 2 kV 1 TA Operating Ambient Temperature -40 +85 C TJ Junction Temperature -40 +150 C TSTG Storage Temperature -65 +150 C +260 C TL Lead Soldering Temperature, 10 Seconds Recommended Operating Conditions The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to absolute maximum ratings. Symbol Parameter VIN VOUT VIN Supply Voltage (1) Min. Typ. Max. Unit 2.3 3.7 5.5 V VOUT Voltage 3.5 8.5 V Full Scale LED Current per Channel 2.5 25.0 mA TA Ambient Temperature -40 +85 C TJ Junction Temperature -40 +125 C ILED(FS) Note: 1. The minimum VOUT must be 3.5 V to guarantee a maximum LED current of 25 mA for each LED pin. Otherwise the device internally sets a minimum VOUT to VIN + 0.3 V, and the LED driver dropout is increased accordingly (if LED VF < VIN, where VF = VOUT - 0.3 V). Thermal Properties Junction-to-ambient thermal resistance is a function of application and board layout. This data is measured with four-layer 2s2p boards in accordance to JEDEC standard JESD51. Special attention must be paid not to exceed junction temperature TJ(max) at a given ambient temperate TA. Symbol Parameter JA Min. Junction-to-Ambient Thermal Resistance Typ. 90 Max. Unit C/W (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 www.fairchildsemi.com 4 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Absolute Maximum Ratings Unless otherwise specified: VIN = 2.3 V to 5.5 V, TA = -40C to +85C, and EN13 and EN45 = "1." Typical values are VIN = 3.7 V, TA = 25C, VOUT = 6.8 V, ILED1-5 = 20 mA. Circuit and components are according to Figure 1. Symbol Parameter Condition Min. Typ. Max. Unit 0.1 4.0 A 2.1 1.9 200 2.2 V V mV Power Supplies ISD VUVLO VUVHYST Device Disabled, (EN13 = EN45 = "0"), VIN = 2.3 V to 4.5 V Rising VIN Under-Voltage Lockout Threshold Falling VIN Under-Voltage Lockout Hysteresis Shutdown Current 1.8 Oscillator fSW Frequency PWM Mode CCM 1.8 MHz Boost Regulator ILIM-PK ISOFT-PK ILOAD Peak Switch Current Limit Soft-Start Peak Switch Current Maximum Continuous (3) Output Current (2) Open Loop, VIN = 2.5 V to 5.5 V 445 Open Loop 525 640 250 VIN > 2.5 V mA mA 100 mA LED Current Driver Characteristics ILED/ILED VLED_DO fPWM Line Transient Response to (3) VIN Variations LED Driver Drop-Out Voltage (3) LED PWM Frequency ILED_MATCH LED Current Matching (3) Relative Response to 350 mV Pulses 10 Response to 350 mV Pulses Integrated Over 20 ms Period 1 (5) 290 100 Variation between Different ILED1 - ILED5 Currents. Matching LED Pin Voltage (4) Difference < 250 mV ILED = 2.5 mA to 10 mA 2.0 5.0 ILED = 10 mA to 25 mA 1.0 3.5 10 PWM 25/255, 300 Hz 2 LED Current Linearity ILED Absolute LED Current Accuracy LED1 - LED5 Peak-to-Peak LED Current (3) Ripple VLED_DO 0.6 V (Typical 0.29 V), fPWM = 300 Hz, Measurement BW = 10 MHz LED Driver Leakage In OFF State ILEAKAGE VISET mV Hz % 1/255 PWM 24/255, 300 Hz ILINEARITY ILED_RIPPLE 800 % ILED = 2.5 mA to 5 mA ILED = 5 mA to 25 mA % 15.0 % 7.5 0.4 ISET Voltage 1.2 mAP-P 0.5 A 1.20 V Logic Control VIL VIH REN13 Logic LOW Threshold Logic HIGH Threshold EN13 Pull-Down Resistor REN45 EN45 Pull-Down Resistor 0.5 1.05 V V 250 k 250 k Continued on the following page... (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 www.fairchildsemi.com 5 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Electrical Specifications Unless otherwise specified: VIN = 2.3 V to 5.5 V, TA = -40C to +85C, and EN13 and EN45 = "1." Typical values are VIN = 3.7 V, VOUT = 6.8 V, TA = 25C, ILED1-5 = 20 mA. Circuit and components are according to Figure 1. Symbol Parameter Condition Min. Typ. Max. Unit Protection TTSD Over-Temperature Shutdown 150 C THYS Over-Temperature Hysteresis 25 C VOV-RISE VOUT Over-Voltage Rising Threshold VOV-FALL VOUT Over-Voltage Falling Threshold VOV-HYS Hysteresis VLED(SC) LED Short Circuit Protection Threshold ILED-SHORT Shorted LED Current 8.25 0.7 LED Short-Circuit Protection Threshold Tripped 9.0 V 8.60 V 400 mV 1.0 1.4 V 1 A Notes: 2. In closed loop operation, the inductor current (IL) is 30 mA to 40 mA greater than ILIM-PK. 3. Guaranteed by characterization and design. 4. For the LED outputs, the following are determined: the maximum LED current in the group (MAX), the minimum LED current in the group (MIN), and the average LED current of the group (AVG). Two matching numbers are calculated: (MAX - AVG) / AVG and (AVG - MIN) / AVG. The larger number of the two (worst case) is considered the matching value for the group. The matching value for a given part is considered to be the highest matching value of the two groups. The typical specification provided is the most likely norm of the matching value for all parts. 5. LED driver drop-out voltage is the smallest voltage across all the LED channels. (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 www.fairchildsemi.com 6 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Electrical Specifications VIN = 3.7 V, TA = 25C, ILED = 5 x 20 mA, VOUT = 6.8 V, L1 = 4.7 H, and COUT = 10 F (unless otherwise specified). Boost Efficiency (%) Boost Efficiency (%) 95 VOUT = 6.8 V 90 VOUT = 5.8 V 85 VOUT = 7.8 V 80 VOUT = 8.8 V 75 70 65 10 30 50 70 90 110 95 SILED = 125 mA SILED = 100 mA 90 SILED = 75 mA 85 SILED = 50 mA 80 75 70 SILED = 12 mA 65 2.50 130 3.50 4.50 VIN (V) Total Output Current (mA) Figure 4. Boost Efficiency vs. Output Current vs. Output Voltage Figure 5. 90 VOUT = 6.8 V System Efficiency (%) System Efficiency (%) 90 85 VOUT = 5.8 V 80 VOUT = 7.8 V VOUT = 8.8 V 75 70 65 10 30 50 70 90 110 130 Boost Efficiency vs. Input Voltage vs. Total LED Current S ILED = 100 mA 85 SILED = 75 mA S ILED = 50 mA 75 70 S ILED = 12 mA 65 2.50 Total Efficiency vs. Output Current vs. Output Voltage 3.50 Figure 7. VIN (V) 4.50 5.50 Total Efficiency vs. Input Voltage vs. Total LED Current 125 Total LED Current (mA) System Efficiency (%) 100 SILED = 125 mA 80 Total Output Current (mA) Figure 6. 5.50 80 60 40 20 0 0 20 40 60 80 100 100 75 50 25 0 0 Total Efficiency vs. PWM Duty Cycle, fPWM = 300 Hz (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 40 60 80 100 PWM Duty Cycle (%) Duty Cycle (%) Figure 8. 20 Figure 9. Total LED Current vs. PWM Duty Cycle, ILED = 5 x 25 mA www.fairchildsemi.com 7 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Typical Characteristics Total Output Current (mA) VIN = 3.7 V, TA = 25C, ILED = 5 x 20 mA, VOUT = 6.8 V, L1 = 4.7 H, COUT = 10 F (unless otherwise specified). 130 500 VOUT = 5.8 V ILED Ripple (A) 120 VOUT = 7.8 V 110 VOUT = 6.8 V 100 VOUT = 8.8 V 90 80 70 2.50 3.50 4.50 300 100 -100 -300 -500 5.50 0 VIN (V) 5 10 15 20 Time (s) Figure 10. Maximum Output Current (ILED = 5 x 25 mA) vs. Input Voltage vs. Output Voltage Figure 11. LED Current Ripple 700 Current (mA) VIN = 3.70V-3.35 V-3.70 V, slope 30 s/V 500 mV/div SILED 10 mA/div 650 600 550 500 2.5 3.0 3.5 Time Base 300s/div Figure 12. Line Transient Response VIN = 3.70 - 3.35 V - 3.70 V with ILED = 5 x 25 mA Total Output Current (mA) Current (A) 0.80 0.60 0.40 0.20 0.00 3.00 3.50 4.00 4.50 5.00 5.50 VIN (V) 5.0 5.5 150 120 90 60 30 0 0 50 100 150 200 RSET Resistance (k) Figure 14. Shutdown Current vs. Input Voltage (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 4.5 Figure 13. Peak Inductor Current Limit (Closed Loop) vs. Input Voltage 1.00 2.50 4.0 VIN (V) Figure 15. Total Output Current ILED vs. RSET Resistor Value www.fairchildsemi.com 8 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Typical Characteristics VIN = 3.7 V, TA = 25C, ILED = 5 x 20 mA, VOUT = 6.8 V, L1 = 4.7 H, COUT = 10 F (unless otherwise specified). ILED CH1...CH5 10 mA/div ILED CH1...CH3 100 mA/div VOUT 1 V/div VOUT 1 V/div VSW 2 V/div VIN 1 V/div ISW 200 mA/div EN13 1 V/div Time Base 400 ns/div Time Base 10 ms/div Figure 16. Switch Waveform (VOUT, VSW, ISW) Figure 17. Startup After Enable, Three Strings Connected ILED CH1...CH4 100 mA/div ILED CH1...CH5 100 mA/div VOUT 1 V/div VOUT 1 V/div VIN 1 V/div VIN 1 V/div EN13=EN45 1 V/div EN13=EN45 1 V/div Time Base 20 ms/div Figure 18. Startup After Enable, Four Strings Connected Time Base 10 ms/div Figure 19. Startup After Enable, Five Strings Connected ILED CH1...CH5 100 mA/div ILED CH1...CH5 100 mA/div VOUT 1 V/div VOUT 1 V/div VIN 1 V/div EN15 1 V/div EN45 1 V/div EN13 1 V/div Time Base 2 ms/div Time Base 20 ms/div Figure 20. LED PWM Startup, Five Strings Connected (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 Figure 21. Startup After LED1-3 Enable Followed by LED4-5 Enable www.fairchildsemi.com 9 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Typical Characteristics VIN = 3.7 V, TA = 25C, ILED = 5 x 20 mA, VOUT = 6.8 V, L1 = 4.7 H, COUT = 10 F (unless otherwise specified). SILED 100 mA/div SILED 100 mA/div VOUT 50 mV/div VOUT 50 mV/div EN45 2 V/div VLED1 2 V/div VLED5 2 V/div EN13 2 V/div Time Base 400 s/div Time Base 400 s/div Figure 22. Asynchronous LED PWM, Two LEDs per LED String Figure 23. Asynchronous LED PWM, Two LEDs on LED1-3 Strings, Single LED on LED4-5 Strings SILED 100 mA/div ILED CH1...CH5 100 mA/div VOUT 50 mV/div VOUT 1 V/div VIN 1 V/div EN45 2 V/div EN13 2 V/div EN15 1 V/div Time Base 1 ms/div Figure 24. Asynchronous LED PWM, All LED Outputs Shorted Together for Common Load See Figure 30 (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 Time Base 10 ms/div Figure 25. Device Disabled, Five Strings Connected www.fairchildsemi.com 10 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Typical Characteristics FAN5776 starts to step up or down to the appropriate regulated voltage. Overview The FAN5776 is a 1.8 MHz synchronous step-up DC-DC converter with integrated constant-current high-side LED drivers capable of driving one to five LED strings up to 5 x 25 mA LED current. 2. At least one LED string in a group is shorted to GND. VOUT rises to 7.5 V while the shorted LED string is disabled and the device starts to step up or down to regulated voltage. The device starts when at least one LED string is utilized and the appropriate EN pin is enabled. The device is disabled in 30 ms by setting both EN pins LOW. 3. At least one LED string is floating or connected to VOUT. VOUT rises to 9.0 V, the floating LED string is disabled, and the device starts to step down to regulated voltage. The VOUT voltage is internally set to 290 mV above the highest LED string voltage, and it is sampled at every falling LED PWM cycle. For 100% duty cycle, the LED-pin voltage is sampled and the VOUT voltage is refined every 10 ms. These functions work for each group independently. If all five strings are utilized and EN13 is HIGH, VOUT rises to 7.5 V (case 1) and goes to the highest voltage required by LED1-3. Then EN45 is raised and VOUT is stepped up again to 7.5 V and regulates to highest voltage required by LED1-5. The LED strings can be disabled by connecting them to VOUT or shorting them to GND. They can also be left disconnected. If the LED string is temporarily disabled or shorted, the device must be re-enabled to enable the string again. If VOUT cannot reach 7.5 V within 1.2 ms after an enable cycle, the device stays disabled and a new enable cycle is required. PWM Dimming The LED drivers work independently and allow multiple LED voltages, such that many types of LEDs can be driven at the same time and some strings can be used to drive a single LED while other channels are driving two LEDs in series. The VOUT voltage is defined by the highest LED voltage and the LED driver dropout voltage is increased to provide the LED string a specific voltage. If the voltage difference between the LED strings is large, the system efficiency may decrease. A LED PWM signal of 100 Hz to 800 Hz can be applied to EN13 and EN45 pins to control LED1-3 and LED4-5 light intensity. The LED current is a linear function of the LED PWM duty cycle from 100% down to 0.4%. The FAN5776 can be started by a PWM signal with a low duty cycle to enable smooth startup. EN13 and EN45 pins can be operated either synchronously or asynchronously, which makes it possible to use the device to backlight two separate displays at the same time. LED Current Under-Voltage Lockout (UVLO) The LED string current is set by the resistor, RSET, between the ISET and GND pins. The same current is applied to across all strings such that total output current: IOUT = 5 x ILED = 5 x 20 mA = 100 mA if RSET = 25 kand all LED strings are used. In general, the LED string current can be calculated as follows: The Under-Voltage Lockout circuitry turns off all MOSFETs and the device remains in a very low quiescent current state until VIN has risen above the UVLO threshold. Short-Circuit Protection (SCP) 500 = The LED driver output current is limited to 0.5 A or less when a LED number pin voltage is below 1.0 V. This limit shall be applied within one LED PWM cycle, or 10 ms, whichever elapses first. (1) LED Current (mA) 25 Over-Voltage Protection (OVP) 20 When the regulator is active, it monitors the VOUT pin. If the VOUT voltage reaches 9.0 V, the regulator stops switching until the capacitor at VOUT discharges below 8.5 V. 15 10 LED-Open Detection If VOUT is detected above >9.0 V, the LED voltages are scanned. All LED pins with voltage greater than VOUT - 0.5 V are disabled. If all LED pins' voltages exceed 8.5 V and VOUT is greater than 9.0 V, device is disabled and a new startup cycle is required. 5 0 20 40 60 80 100 120 140 160 180 200 Resistor RSET (k) Over-Current Protection (OCP) The PWM converter is protected against overload through cycle-by cycle current limit using a fixed internal limit. Figure 26. LED Current vs. RSET Value Startup Thermal Shutdown The three different startup functions depend on the system configuration: 1. When the die temperature exceeds 150C, reset occurs and remains in effect until the die cools to 125C; at which time, the circuit enters the normal soft-start sequence. All LED strings are utilized: Setting one or both EN pins HIGH enables the device and VOUT rises to 7.5 V. (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 www.fairchildsemi.com 11 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Circuit Description External Component Selection Four external components are required to power the FAN5776: an inductor between the VIN and SW pins, storage capacitor at the output, storage capacitor at the input, and reference resistor at the ISET pin. The inductor's minimum inductance requirement is 2.45 H with an ESR 300 m at 500 mA bias current at 1.8 MHz frequency. A lower inductance drops device efficiency, while a higher inductance reduces output ripple. The minimum capacitance for the output capacitor is 4.8 F at 5 V. Note that the ceramic capacitor value depends on the DC bias voltage. Check the datasheet of the capacitor to make sure the capacitor meets all specifications. Figure 28. Schematic for Recommended Layout Startup Power Minimization The FAN5776 is optimized to minimize startup power when all five LED driver outputs are connected to LEDs. Where some of the LED strings are not used due to smaller LCD display size, the startup power can still be minimized. Connecting the unused LED driver outputs to ground (GND) prevents LED current drop during startup and VOUT starts at 7.5 V, which reduces power consumption. Secondly, the unused LED driver outputs connected to GND are disabled at startup, minimizing the leakage current to GND. If left open the unused LED strings cause VOUT to rise to the OVP voltage of 9.0 V instead of starting at 7.5 V. The device detects an open circuit due to the unused LED strings and therefore goes up to 9.0 V, then adjusts to a VOUT that is appropriate to power the LED strings. An input capacitor of 2.2 F is recommended to improve device's transient behavior. Ensure the VIN supply voltage is ripple-free for optimal device performance. The reference resistor value is at least 20 k. The LED current accuracy is defined by this resistor and a highprecision resistor with low temperature dependency is recommended. To guarantee the FAN5776 performance and achieve ILED maximum current of 25 mA, 20 k, 1% or better resistor must be used. PCB Layout Guidelines A separate ground plane is recommended to minimize noise. Place the FAN5776 device, inductor (L), CIN and COUT capacitors, and their interconnections on the same side of the board. High-current paths from the supply voltage to the SW pin via the inductor, and GND pin to ground plane, are recommended as low resistance paths. Keep the VOUT-pinto-COUT-capacitor path as short as possible to minimize the inductance of the VOUT-pin-to-COUT for low VOUT ripple voltage. Minimize the SW pin capacitance to realize optimum system efficiency. Keep the ISET-pin-to-RSET-resistor path away from noisy signals (SW pin) to minimize crosstalk from the SW pin to the ISET pin. The device is also working to specification when un-used LED drivers are connected to the VOUT pin or left floating. Combined LCD Backlight and Blinker Figure 29. Schematic for Screen Backlight and Blinker The FAN5776 can be utilized for different lighting applications by configuring it to suit the design requirements. Each LED driver output is independent such that each output can support a different output voltage while being controlled simultaneously. Configuring the FAN5776 with a different number of LEDs for each output results in a lower system efficiency because the outputs with a single LED have a higher dropout voltage compared to the outputs with two LEDs in series. The system efficiency () is calculated as follows: Figure 27. Recommended PCB Layout (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 www.fairchildsemi.com 12 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Applications = =1 Figure 29 illustrates an application where the FAN5776 uses three LED outputs (LED1 to LED3) with two LEDs in series per channel to backlight the main LCD display, while LED5 powers a single LED for blinking functionality. LED4 is unused and connected to GND. Backlighting and PWM dimming of the LEDs for the LCD display are controlled by EN13, while EN45 controls the blinking and dimming level for LED5. (2) where: Ii is the LED(i) channel current; Vi is the LED(i) channel voltage; IIN is the supply current (rms); and VIN is the supply voltage (rms). If all the LED strings are equivalent, I1 = I2 = ... = I5 and V1 = V2 = ... = V5 and N channels are used (N = 1, 2, 3, 4 or 5), the equation simplifies to: = (3) where: ILED is the LED channel current (total output current is N*ILED) and VLED is the LED channel voltage. Figure 30. Schematic for Flashlight Applications To use FAN5776 as an LED flashlight driver, as shown in Figure 30, connect VIN to the battery voltage and add a single-pole switch (mechanical or electrical) from EN13 and/or EN45 pins to VIN. Pull-down resistors on the EN pins disable the device when the switch is in a non-conducting state. There are two LED output groups with separate control for each group. EN13 and EN45 pins are the control/PWM for LED1-3 and LED4-5 outputs, respectively. (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 www.fairchildsemi.com 13 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver 5 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver Physical Dimensions 0.03 C E 2X F A 0.80 B 1.20 0.40 PIN A1 AREA D (O0.200) Cu Pad (O0.300) Solder Mask 0.40 0.03 C 2X TOP VIEW RECOMMENDED LAND PATTERN (NSMD PAD TYPE) 0.2920.018 0.539 0.461 0.05 C 0.2080.021 0.06 C C SEATING PLANE D SIDE VIEWS 0.005 0.80 O0.2600.02 12X 0.40 1.20 NOTES: A. NO JEDEC REGISTRATION APPLIES. B. DIMENSIONS ARE IN MILLIMETERS. D C B A 0.40 C A B (Y)0.018 F 1 2 3 (X)0.018 C. DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994. D. DATUM C IS DEFINED BY THE SPHERICAL CROWNS OF THE BALLS. E. PACKAGE NOMINAL HEIGHT IS 500 MICRONS 39 MICRONS (461-539 MICRONS). BOTTOM VIEW F. FOR DIMENSIONS D, E, X, AND Y SEE PRODUCT DATASHEET. G. DRAWING FILENAME: MKT-UC012ADrev1. Figure 31. 12-Bump, Wafer-Level Chip-Scale Package (WLCSP) 1.42 x 1.66 x 0.50 mm, 0.40 mm Pitch Product-Specific Dimensions D E X Y 1.660 mm 1.420 mm 0.310 mm 0.230 mm Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or obtain the most recent revision. Package specifications do not expand the terms of Fairchild's worldwide terms and conditions, specifically the warranty therein, which covers Fairchild products. Always visit Fairchild Semiconductor's online packaging area for the most recent package drawings: http://www.fairchildsemi.com/dwg/UC/UC012AD.pdf. (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 www.fairchildsemi.com 14 FAN5776 -- Synchronous Boost and Series/Parallel 10-LED Driver (c) 2010 Fairchild Semiconductor Corporation FAN5776 * Rev. 1.1.0 www.fairchildsemi.com 15 ON Semiconductor and are trademarks of Semiconductor Components Industries, LLC dba ON Semiconductor or its subsidiaries in the United States and/or other countries. ON Semiconductor owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of ON Semiconductor's product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent-Marking.pdf. ON Semiconductor reserves the right to make changes without further notice to any products herein. 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