Sample & Buy Product Folder Support & Community Tools & Software Technical Documents LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 LM3405A 1.6-MHz, 1-A Constant Current Buck LED Driver With Internal Compensation in Tiny SOT and MSOP-PowerPADTM Packages 1 Features 3 Description * * The LM3405A is a 1-A constant current buck LED driver designed to provide a simple, high efficiency solution for driving high power LEDs. With a 0.205-V reference voltage feedback control to minimize power dissipation, an external resistor sets the current as needed for driving various types of LEDs. Switching frequency is internally set to 1.6 MHz, allowing small surface mount inductors and capacitors to be used. The LM3405A uses current-mode control and internal compensation offering ease of use and predictable, high performance regulation over a wide range of operating conditions. With a maximum input voltage of 22 V, the device can drive up to 5 High-Brightness LEDs in series at 1-A forward current, with the single LED forward voltage of approximately 3.7 V. Additional features include user accessible EN/DIM pin for enabling and PWM dimming of LEDs, thermal shutdown, cycle-by-cycle current limit and overcurrent protection. 1 * * * * * * * * * * VIN Operating Range of 3 V to 22 V Drives up to 5 High-Brightness LEDs in Series at 1A Thin SOT-6 and MSOP-PowerPADTM-8 Packages 1.6-MHz Switching Frequency EN/DIM Input for Enabling and PWM Dimming of LEDs 300-m NMOS Switch 40-nA Shutdown Current at VIN = 5 V Internally Compensated Current-mode Control Cycle-by-Cycle Current Limit Input Voltage UVLO Overcurrent Protection Thermal Shutdown 2 Applications * * * * * Device Information(1) LED Drivers Constant Current Sources Industrial Lighting LED Flashlights LED Lightbulbs PART NUMBER LM3405A VIN BODY SIZE (NOM) 2.90 mm x 1.60 mm MSOP-PowerPAD (8) 3.00 mm x 3.00 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. Typical Application Circuit D3 PACKAGE SOT (6) Efficiency vs LED Current (VIN = 12 V) D2 BOOST VIN C3 C1 L1 VOUT SW ON LM3405A D1 C2 OFF IF C4 EN/DIM FB GND R1 Copyright (c) 2016, Texas Instruments Incorporated 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 4 6.1 6.2 6.3 6.4 6.5 6.6 4 4 4 5 5 6 Absolute Maximum Ratings ..................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics........................................... Typical Characteristics .............................................. Detailed Description .............................................. 8 7.1 7.2 7.3 7.4 Overview ................................................................... 8 Functional Block Diagram ......................................... 9 Feature Description................................................... 9 Device Functional Modes........................................ 14 8 Application and Implementation ........................ 15 8.1 Application Information............................................ 15 8.2 Typical Applications ................................................ 19 8.3 System Examples ................................................... 21 9 Power Supply Recommendations...................... 25 10 Layout................................................................... 25 10.1 Layout Guidelines ................................................. 25 10.2 Layout Example .................................................... 25 11 Device and Documentation Support ................. 26 11.1 11.2 11.3 11.4 11.5 11.6 Documentation Support ........................................ Receiving Notification of Documentation Updates Community Resource............................................ Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 26 26 26 26 26 26 12 Mechanical, Packaging, and Orderable Information ........................................................... 26 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision C (May 2013) to Revision D Page * Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section ................................................................................................. 1 * Changed RJA for SOT package from 118C/W to 182.9C/W............................................................................................... 5 * Changed RJA for MSOP package from 73C/W to 55.3C/W................................................................................................ 5 Changes from Revision B (April 2013) to Revision C * 2 Page Changed layout of National Semiconductor Data Sheet to TI format .................................................................................. 23 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 5 Pin Configuration and Functions DDC Package 6-Pin SOT Top View DGN Package 8-Pin MSOP-PowerPADTM Top View BOOST 1 6 SW GND 2 5 VIN FB 3 4 EN/DIM FB 1 8 EN/DIM 7 GND GND 2 NC 3 6 VIN BOOST 4 5 SW Pin Functions PIN I/O DESCRIPTION NAME SOT MSOP-PowerPAD BOOST 1 4 O Boost voltage that drives the NMOS output switch. A bootstrap capacitor is connected between the BOOST and SW pins. GND 2 2, 7 -- Signal and power ground pin. Place the bottom resistor of the feedback network as close as possible to this pin. FB 3 1 I Feedback pin. Connect FB to the LED string cathode and an external resistor to ground to set the LED current. EN/DIM 4 8 I Enable control input. Logic high enables operation. Toggling this pin with a periodic logic square wave of varying duty cycle at different frequencies controls the brightness of LEDs. Do not allow this pin to float or be greater than VIN + 0.3 V. VIN 5 6 I Input supply voltage. Connect a bypass capacitor locally from this pin to GND. SW 6 5 O Switch pin. Connect this pin to the inductor, catch diode, and bootstrap capacitor. -- 3 -- No connection. N/A -- -- Attach to power ground pin (GND). NC DAP Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 3 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com 6 Specifications 6.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) (1) MIN MAX UNIT VIN -0.5 24 V SW voltage -0.5 24 V Boost voltage -0.5 30 V Boost to SW voltage -0.5 6 V FB voltage -0.5 3 V EN/DIM voltage -0.5 (VIN + 0.3) V 150 C 150 C Junction temperature, TJ Storage temperature, Tstg (1) -65 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. 6.2 ESD Ratings VALUE UNIT LM3405A IN SOT PACKAGE V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) 2000 Charged-device model (CDM), per JEDEC specification JESD22-C101 (2) 1000 V LM3405A IN MSOP-PowerPAD PACKAGE V(ESD) (1) (2) Electrostatic discharge Charged-device model (CDM), per JEDEC specification JESD22-C101 (2) 750 V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. 6.3 Recommended Operating Conditions VIN EN/DIM voltage MIN MAX 3 22 UNIT V V 0 (VIN + 0.3) Boost to SW voltage 2.5 5.5 V Junction temperature -40 125 C 400 mA ILED 4 SOT package MSOP-PowerPAD package 1 Submit Documentation Feedback A Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 6.4 Thermal Information LM3405A THERMAL METRIC (1) DDC (SOT) DGN (MSOP-PowerPAD) UNIT 6 PINS 8 PINS RJA Junction-to-ambient thermal resistance 182.9 55.3 C/W RJC(top) Junction-to-case (top) thermal resistance 53.4 62.8 C/W RJB Junction-to-board thermal resistance 28.1 38.9 C/W JT Junction-to-top characterization parameter 1.2 8.2 C/W JB Junction-to-board characterization parameter 27.7 38.6 C/W RJC(bot) Junction-to-case (bottom) thermal resistance N/A 8 C/W (1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report. 6.5 Electrical Characteristics Unless otherwise specified, VIN = 12 V. TYP values are for TJ = 25C only; MIN/MAX limits apply over the junction temperature (TJ) range of -40C to 125C. Typical values represent the most likely parametric norm, and are provided for reference purposes only. PARAMETER TEST CONDITIONS VFB Feedback voltage VFB/(VINxVFB) Feedback voltage line regulation VIN = 3 V to 22 V IFB Feedback input bias current Sink/source UVLO Undervoltage lockout MIN TYP MAX UNIT 0.188 0.205 0.22 V 0.01 VIN Rising VIN Falling 1.9 UVLO Hysteresis 10 250 nA 2.74 2.95 V 2.3 V 0.44 fSW Switching frequency DMAX Maximum duty cycle RDS(ON) Switch ON resistance ICL Switch current limit VBOOST - VSW = 3 V, VIN = 3 V Quiescent current Switching, VFB = 0.195 V Quiescent current (shutdown) VEN/DIM = 0 V 0.3 IQ %/V VFB = 0 V 1.2 1.6 85% 94% V 1.9 MHz SOT (VBOOST - VSW = 3 V) 300 600 MSOP-PowerPAD (VBOOST - VSW = 3 V) 360 700 2 2.8 A 1.8 2.8 mA Enable threshold voltage VEN/DIM Rising VEN/DIM_TH Shutdown threshold voltage VEN/DIM Falling IEN/DIM EN/DIM pin current Sink/Source ISW Switch leakage VIN = 22 V 1.2 A 1.8 V 0.4 Product Folder Links: LM3405A V 0.01 A 0.1 A Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated m 5 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com 6.6 Typical Characteristics Unless otherwise specified, VIN = 12 V, VBOOST - VSW = 5 V and TA = 25C. IF = 1 A VIN = 5 V Figure 2. Efficiency vs Input Voltage Figure 1. Efficiency vs LED Current IF = 0.7 A 6 IF = 0.35 A Figure 3. Efficiency vs Input Voltage Figure 4. Efficiency vs Input Voltage Figure 5. VFB vs Temperature Figure 6. Oscillator Frequency vs Temperature Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 Typical Characteristics (continued) Unless otherwise specified, VIN = 12 V, VBOOST - VSW = 5 V and TA = 25C. VBOOST - VSW = 3 V Figure 7. Current Limit vs Temperature Figure 8. SOT RDS(ON) vs Temperature VIN = 15 V Figure 9. Quiescent Current vs Temperature IF = 0.2 A Figure 10. Start-Up Response to EN/DIM Signal Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 7 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com 7 Detailed Description 7.1 Overview The LM3405A is a PWM, current-mode controlled buck switching regulator designed to provide a simple, high efficiency solution for driving LEDs with a preset switching frequency of 1.6MHz. This high frequency allows the LM3405A to operate with small surface mount capacitors and inductors, resulting in LED drivers that need only a minimum amount of board space. The LM3405A is internally compensated, simple to use, and requires few external components. The following description of operation of the LM3405A refers to the Typical Application Circuit and to the waveforms in Figure 11. The LM3405A supplies a regulated output current by switching the internal NMOS power switch at constant frequency and variable duty cycle. A switching cycle begins at the falling edge of the reset pulse generated by the internal oscillator. When this pulse goes low, the output control logic turns on the internal NMOS power switch. During this on-time, the SW pin voltage (VSW) swings up to approximately VIN, and the inductor current (IL) increases with a linear slope. IL is measured by the current sense amplifier, which generates an output proportional to the switch current. The sense signal is summed with the regulator's corrective ramp and compared to the error amplifier's output, which is proportional to the difference between the feedback voltage and VREF. When the PWM comparator output goes high, the internal power switch turns off until the next switching cycle begins. During the switch off-time, inductor current discharges through the catch diode D1, which forces the SW pin to swing below ground by the forward voltage (VD1) of the catch diode. The regulator loop adjusts the duty cycle (D) to maintain a constant output current (IF) through the LED, by forcing FB pin voltage to be equal to VREF (0.205 V). VSW D = TON/TSW VIN SW Voltage TOFF TON 0 -VD1 IL t TSW ILPK IF 'iL Inductor Current t 0 Figure 11. SW Pin Voltage and Inductor Current Waveforms of LM3405A 8 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 7.2 Functional Block Diagram Copyright (c) 2016, Texas Instruments Incorporated 7.3 Feature Description 7.3.1 Boost Function Capacitor C3 and diode D2 in the Functional Block Diagram are used to generate a voltage VBOOST. The voltage across C3, VBOOST - VSW, is the gate drive voltage to the internal NMOS power switch. To properly drive the internal NMOS switch during its on-time, VBOOST needs to be at least 2.5-V greater than VSW. A large value of VBOOST - VSW is recommended to achieve better efficiency by minimizing both the internal switch ON resistance (RDS(ON)), and the switch rise and fall times. However, VBOOST - VSW should not exceed the maximum operating limit of 5.5 V. When the LM3405A starts up, internal circuitry from VIN supplies a 20-mA current to the BOOST pin, flowing out of the BOOST pin into C3. This current charges C3 to a voltage sufficient to turn the switch on. The BOOST pin will continue to source current to C3 until the voltage at the feedback pin is greater than 123 mV. There are various methods to derive VBOOST: 1. From the input voltage (VIN) 2. From the output voltage (VOUT) 3. From a shunt or series Zener diode 4. From an external distributed voltage rail (VEXT) The first method is shown in the Functional Block Diagram. Capacitor C3 is charged via diode D2 by VIN. During a normal switching cycle, when the internal NMOS power switch is off (TOFF) (see Figure 11), VBOOST equals VIN minus the forward voltage of D2 (VD2), during which the current in the inductor (L1) forward biases the catch diode D1 (VD1). Therefore the gate drive voltage stored across C3 is: VBOOST - VSW = VIN - VD2 + VD1 (1) When the NMOS switch turns on (TON), the switch pin rises to: VSW = VIN - (RDS(ON) x IL) (2) Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 9 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com Feature Description (continued) Since the voltage across C3 remains unchanged, VBOOST is forced to rise thus reverse biasing D2. The voltage at VBOOST is then: VBOOST = 2VIN - (RDS(ON) x IL) - VD2 + VD1 (3) Depending on the quality of the diodes D1 and D2, the gate drive voltage in this method can be slightly less or larger than the input voltage VIN. For best performance, ensure that the variation of the input supply does not cause the gate drive voltage to fall outside the recommended range: 2.5V < VIN - VD2 + VD1 < 5.5 V (4) The second method for deriving the boost voltage is to connect D2 to the output as shown in Figure 12. The gate drive voltage in this configuration is: VBOOST - VSW = VOUT - VD2 + VD1 (5) Since the gate drive voltage needs to be in the range of 2.5 V to 5.5 V, the output voltage VOUT should be limited to a certain range. For the calculation of VOUT, see Output Voltage. Copyright (c) 2016, Texas Instruments Incorporated Figure 12. VBOOST Derived from VOUT The third method can be used in the applications where both VIN and VOUT are greater than 5.5 V. In these cases, C3 cannot be charged directly from these voltages; instead C3 can be charged from VIN or VOUT minus a Zener voltage (VD3) by placing a Zener diode D3 in series with D2 as shown in Figure 13. When using a series Zener diode from the input, the gate drive voltage is VIN - VD3 - VD2 + VD1. Copyright (c) 2016, Texas Instruments Incorporated Figure 13. VBOOST Derived from VIN Through a Series Zener 10 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 Feature Description (continued) An alternate method is to place the zener diode D3 in a shunt configuration as shown in Figure 14. A small 350 mW to 500 mW, 5.1-V Zener in a SOT or SOD package can be used for this purpose. A small ceramic capacitor such as a 6.3 V, 0.1-F capacitor (C5) should be placed in parallel with the Zener diode. When the internal NMOS switch turns on, a pulse of current is drawn to charge the internal NMOS gate capacitance. The 0.1-F parallel shunt capacitor ensures that the VBOOST voltage is maintained during this time. Resistor R2 should be chosen to provide enough RMS current to the zener diode and to the BOOST pin. A recommended choice for the zener current (IZENER) is 1 mA. The current IBOOST into the BOOST pin supplies the gate current of the NMOS power switch. It reaches a maximum of around 3.6 mA at the highest gate drive voltage of 5.5 V over the LM3405A operating range. For the worst case IBOOST, increase the current by 50%. In that case, the maximum boost current will be: IBOOST-MAX = 1.5 x 3.6 mA = 5.4 mA (6) R2 will then be given by: R2 = (VIN - VZENER) / (IBOOST_MAX + IZENER) (7) For example, let VIN = 12 V, VZENER = 5V, IZENER = 1 mA, then: R2 = (12 V - 5 V) / (5.4 mA + 1 mA) = 1.09 k (8) Copyright (c) 2016, Texas Instruments Incorporated Figure 14. VBOOST Derived from VIN Through a Shunt Zener The fourth method can be used in an application which has an external low voltage rail, VEXT. C3 can be charged through D2 from VEXT, independent of VIN and VOUT voltage levels. Again for best performance, ensure that the gate drive voltage, VEXT - VD2 + VD1, falls in the range of 2.5 V to 5.5 V. 7.3.2 Setting the LED Current LM3405A is a constant current buck regulator. The LEDs are connected between VOUT and the FB pin as shown in the Typical Application Circuit. The FB pin is at 0.205V in regulation and therefore the LED current IF is set by VFB and resistor R1 from FB to ground by the following equation: IF = VFB / R1 (9) IF should not exceed the 1-A current capability of LM3405A and therefore R1 minimum must be approximately 0.2 . IF should also be kept above 200 mA for stable operation, and therefore R1 maximum must be approximately 1 . If average LED currents less than 200 mA are desired, the EN/DIM pin can be used for PWM dimming. See LED PWM Dimming. 7.3.3 Output Voltage The output voltage is primarily determined by the number of LEDs (n) connected from VOUT to FB pin and therefore VOUT can be written as: VOUT = ((n x VF) + VFB) Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 11 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com Feature Description (continued) where * VF is the forward voltage of one LED at the set LED current level (see LED manufacturer data sheet for forward characteristics curve) (10) 7.3.4 Enable Mode / Shutdown Mode The LM3405A has both enable and shutdown modes that are controlled by the EN/DIM pin. Connecting a voltage source greater than 1.8 V to the EN/DIM pin enables the operation of LM3405A, while reducing this voltage below 0.4 V places the part in a low quiescent current (0.3 A typical) shutdown mode. There is no internal pullup on EN/DIM pin, therefore an external signal is required to initiate switching. Do not allow this pin to float or rise to 0.3 V above VIN. It should be noted that when the EN/DIM pin voltage rises above 1.8 V while the input voltage is greater than UVLO, there is a finite delay before switching starts. During this delay the LM3405A will go through a power on reset state after which the internal soft-start process commences. The soft-start process limits the inrush current and brings up the LED current (IF) in a smooth and controlled fashion. The total combined duration of the power on reset delay, soft-start delay and the delay to fully establish the LED current is in the order of 100 s (see Figure 19). The simplest way to enable the operation of LM3405A is to connect the EN/DIM pin to VIN which allows self startup of LM3405A whenever the input voltage is applied. However, when an input voltage of slow rise time is used to power the application and if both the input voltage and the output voltage are not fully established before the soft-start time elapses, the control circuit will command maximum duty cycle operation of the internal power switch to bring up the output voltage rapidly. When the feedback pin voltage exceeds 0.205 V, the duty cycle will have to reduce from the maximum value accordingly, to maintain regulation. It takes a finite amount of time for this reduction of duty cycle and this will result in a spike in LED current for a short duration as shown in Figure 15. In applications where this LED current overshoot is undesirable, EN/DIM pin voltage can be separately applied and delayed such that VIN is fully established before the EN/DIM pin voltage reaches the enable threshold. The effect of delaying EN/DIM with respect to VIN on the LED current is shown in Figure 16. For a fast rising input voltage (200 s for example), there is no need to delay the EN/DIM signal since soft-start can smoothly bring up the LED current as shown in Figure 17. Figure 15. Start-Up Response to VIN With 5-ms Rise Time 12 Figure 16. Start-Up Response to VIN With EN/DIM Delayed Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 Feature Description (continued) Figure 17. Start-Up Response to VIN With 200-s Rise Time 7.3.5 LED PWM Dimming The LED brightness can be controlled by applying a periodic pulse signal to the EN/DIM pin and varying its frequency and/or duty cycle. This so-called PWM dimming method controls the average light output by pulsing the LED current between the set value and zero. A logic high level at the EN/DIM pin turns on the LED current whereas a logic low level turns off the LED current. Figure 18 shows a typical LED current waveform in PWM dimming mode. As explained in the previous section, there is approximately a 100-s delay from the EN/DIM signal going high to fully establishing the LED current as shown in Figure 19. This 100-s delay sets a maximum frequency limit for the driving signal that can be applied to the EN/DIM pin for PWM dimming. Figure 20 shows the average LED current versus duty cycle of PWM dimming signal for various frequencies. The applicable frequency range to drive LM3405A for PWM dimming is from 100 Hz to 5 kHz. The dimming ratio reduces drastically when the applied PWM dimming frequency is greater than 5 kHz. Figure 18. PWM Dimming of LEDs Using the EN/DIM Pin Figure 19. Start-Up Response to EN/DIM With IF = 1 A Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 13 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com Feature Description (continued) Figure 20. Average LED Current vs Duty Cycle of PWM Dimming Signal at EN/DIM Pin 7.3.6 Undervoltage Lockout Undervoltage lockout (UVLO) prevents the LM3405A from operating until the input voltage exceeds 2.74 V (typical). The UVLO threshold has approximately 440 mV of hysteresis, so the part will operate until VIN drops below 2.3 V (typical). Hysteresis prevents the part from turning off during power up if VIN is non-monotonic. 7.3.7 Current Limit The LM3405A uses cycle-by-cycle current limit to protect the internal power switch. During each switching cycle, a current limit comparator detects if the power switch current exceeds 2 A (typical), and turns off the switch until the next switching cycle begins. 7.3.8 Overcurrent Protection The LM3405A has a built-in overcurrent comparator that compares the FB pin voltage to a threshold voltage that is 60% higher than the internal reference VREF. Once the FB pin voltage exceeds this threshold level (typically 328 mV), the internal NMOS power switch is turned off, which allows the feedback voltage to decrease towards regulation. This threshold provides an upper limit for the LED current. LED current overshoot is limited to 328 mV/R1 by this comparator during transients. 7.4 Device Functional Modes 7.4.1 Thermal Shutdown Thermal shutdown limits total power dissipation by turning off the internal power switch when the IC junction temperature exceeds 165C. After thermal shutdown occurs, the power switch does not turn on until the junction temperature drops below approximately 150C. 14 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI's customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information 8.1.1 Inductor (L1) The Duty Cycle (D) can be approximated quickly using the ratio of output voltage (VOUT) to input voltage (VIN): D= VOUT VIN (11) The catch diode (D1) forward voltage drop and the voltage drop across the internal NMOS must be included to calculate a more accurate duty cycle. Calculate D by using Equation 12: VOUT + VD1 D= VIN + VD1 - VSW (12) VSW can be approximated by Equation 13: VSW = IF x RDS(ON) (13) The diode forward drop (VD1) can range from 0.3 V to 0.7 V depending on the quality of the diode. The lower VD1 is, the higher the operating efficiency of the converter. The inductor value determines the output ripple current (iL, as defined in Figure 11). Lower inductor values decrease the size of the inductor, but increases the output ripple current. An increase in the inductor value will decrease the output ripple current. The ratio of ripple current to LED current is optimized when it is set between 0.3 and 0.4 at 1A LED current. This ratio r is defined as: r= 'iL lF (14) One must also ensure that the minimum current limit (1.2 A) is not exceeded, so the peak current in the inductor must be calculated. The peak current (ILPK) in the inductor is calculated as: ILPK = IF + iL/2 (15) When the designed maximum output current is reduced, the ratio r can be increased. At a current of 0.2 A, r can be made as high as 0.7. The ripple ratio can be increased at lighter loads because the net ripple is actually quite low, and if r remains constant the inductor value can be made quite large. An equation empirically developed for the maximum ripple ratio at any current below 2 A is: r = 0.387 x IOUT-0.3667 (16) Note that this is just a guideline. The LM3405A operates at a high frequency allowing the use of ceramic output capacitors without compromising transient response. Ceramic capacitors allow higher inductor ripple without significantly increasing LED current ripple. See the output capacitor and feed-forward capacitor sections for more details on LED current ripple. Now that the ripple current or ripple ratio is determined, the inductance is calculated by Equation 17: L= VOUT + VD1 IF x r x fSW x (1-D) where * * fSW is the switching frequency IF is the LED current (17) Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 15 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com Application Information (continued) When selecting an inductor, make sure that it is capable of supporting the peak output current without saturating. Inductor saturation will result in a sudden reduction in inductance and prevent the regulator from operating correctly. Because of the operating frequency of the LM3405A, ferrite based inductors are preferred to minimize core losses. This presents little restriction since the variety of ferrite based inductors is huge. Lastly, inductors with lower series resistance (DCR) will provide better operating efficiency. For recommended inductor selection, refer to Circuit Examples and Recommended Inductance Range in Table 1. Table 1. Recommended Inductance Range IF INDUCTANCE RANGE AND INDUCTOR CURRENT RIPPLE 6.8 H-15 H 1A Inductance 6.8 H 10 H 15 H iL / IF (1) 51% 36% 24% 10 H-22 H 0.6 A Inductance 10 H 15 H 22 H iL / IF (1) 58% 39% 26% 15 H-27 H 0.2 A (1) Inductance 15 H 22 H 27 H iL / IF (1) 116% 79% 65% Maximum over full range of VIN and VOUT. 8.1.2 Input Capacitor (C1) An input capacitor is necessary to ensure that VIN does not drop excessively during switching transients. The primary specifications of the input capacitor are capacitance, voltage rating, RMS current rating, and ESL (Equivalent Series Inductance). The input voltage rating is specifically stated by the capacitor manufacturer. Make sure to check any recommended deratings and also verify if there is any significant change in capacitance at the operating input voltage and the operating temperature. The input capacitor maximum RMS input current rating (IRMS-IN) must be greater than: IRMS-IN = IF x r2 Dx 1-D+ 12 (18) It can be shown from the above equation that maximum RMS capacitor current occurs when D = 0.5. Always calculate the RMS at the point where the duty cycle D, is closest to 0.5. The ESL of an input capacitor is usually determined by the effective cross sectional area of the current path. A large leaded capacitor will have high ESL and an 0805 ceramic chip capacitor will have very low ESL. At the operating frequency of the LM3405A, certain capacitors may have an ESL so large that the resulting inductive impedance (2fL) will be higher than that required to provide stable operation. It is strongly recommended to use ceramic capacitors due to their low ESR and low ESL. A 10F multilayer ceramic capacitor (MLCC) is a good choice for most applications. In cases where large capacitance is required, use surface mount capacitors such as Tantalum capacitors and place at least a 1F ceramic capacitor close to the VIN pin. For MLCCs it is recommended to use X7R or X5R dielectrics. Consult capacitor manufacturer datasheet to see how rated capacitance varies over operating conditions. 8.1.3 Output Capacitor (C2) The output capacitor is selected based upon the desired reduction in LED current ripple. A 1F ceramic capacitor results in very low LED current ripple for most applications. Due to the high switching frequency, the 1F capacitor alone (without feed-forward capacitor C4) can filter more than 90% of the inductor current ripple for most applications where the sum of LED dynamic resistance and R1 is larger than 1. Since the internal compensation is tailored for small output capacitance with very low ESR, it is strongly recommended to use a ceramic capacitor with capacitance less than 3.3F. 16 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 Given the availability and quality of MLCCs and the expected output voltage of designs using the LM3405A, there is really no need to review other capacitor technologies. A benefit of ceramic capacitors is their ability to bypass high frequency noise. A certain amount of switching edge noise will couple through the parasitic capacitances in the inductor to the output. A ceramic capacitor will bypass this noise. In cases where large capacitance is required, use Electrolytic or Tantalum capacitors with large ESR, and verify the loop performance on the bench. Like the input capacitor, multilayer ceramic capacitors are recommended X7R or X5R. Again, verify actual capacitance at the desired operating voltage and temperature. Check the RMS current rating of the capacitor. The maximum RMS current rating of the capacitor is: IRMS-OUT = IF x r 12 (19) One may select a 1206 size ceramic capacitor for C2 since its current rating is typically higher than 1A, more than enough for the requirement. 8.1.4 Feed-Forward Capacitor (C4) The feed-forward capacitor (designated as C4) connected in parallel with the LED string is required to provide multiple benefits to the LED driver design. It greatly improves the large signal transient response and suppresses LED current overshoot that may otherwise occur during PWM dimming; it also helps to shape the rise and fall times of the LED current pulse during PWM dimming thus reducing EMI emission; it reduces LED current ripple by bypassing some of inductor ripple from flowing through the LED. For most applications, a 1-F ceramic capacitor is sufficient. In fact, the combination of a 1F feed-forward ceramic capacitor and a 1F output ceramic capacitor leads to less than 1% current ripple flowing through the LED. Lower and higher C4 values can be used, but bench validation is required to ensure the performance meets the application requirement. Figure 21 shows a typical LED current waveform during PWM dimming without feed-forward capacitor. At the beginning of each PWM cycle, overshoot can be seen in the LED current. Adding a 1F feed-forward capacitor can totally remove the overshoot as shown in Figure 22. Figure 21. PWM Dimming Without Feed-Forward Capacitor Figure 22. PWM Dimming With a 1-F Feed-Forward Capacitor 8.1.5 Catch Diode (D1) The catch diode (D1) conducts during the switch off-time. A Schottky diode is required for its fast switching time and low forward voltage drop. The catch diode should be chosen such that its current rating is greater than: ID1 = IF x (1-D) (20) The reverse breakdown rating of the diode must be at least the maximum input voltage plus appropriate margin. To improve efficiency, choose a Schottky diode with a low forward voltage drop. Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 17 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com 8.1.6 Boost Diode (D2) A standard diode such as the 1N4148 type is recommended. For VBOOST circuits derived from voltages less than 3.3V, a small-signal Schottky diode is recommended for better efficiency. A good choice is the BAT54 small signal diode. 8.1.7 Boost Capacitor (C3) A 0.01F ceramic capacitor with a voltage rating of at least 6.3V is sufficient. The X7R and X5R MLCCs provide the best performance. 8.1.8 Power Loss Estimation The main power loss in LM3405A includes three basic types of loss in the internal power switch: conduction loss, switching loss, and gate charge loss. In addition, there is loss associated with the power required for the internal circuitry of IC. The conduction loss is calculated as: 2 1 'iL * * u PCOND IF2 u D u 1 u RDS(ON) 3 (c) IF (c) (21) If the inductor ripple current is fairly small (for example, less than 40%) , the conduction loss can be simplified to: PCOND = IF2 x RDS(ON) x D (22) The switching loss occurs during the switch on and off transition periods, where voltage and current overlap resulting in power loss. The simplest means to determine this loss is to empirically measure the rise and fall times (10% to 90%) of the voltage at the switch pin. Switching power loss is calculated as follows: PSW = 0.5 x VIN x IF x fSW x ( TRISE + TFALL ) (23) The gate charge loss is associated with the gate charge QG required to drive the switch: PG = fSW x VIN x QG (24) The power loss required for operation of the internal circuitry: PQ = IQ x VIN (25) IQ is the quiescent operating current, and is typically around 1.8mA for the LM3405A. The total power loss in the IC is: PINTERNAL = PCOND + PSW + PG + PQ (26) An example of power losses for a typical application is shown in Table 2: Table 2. Power Loss Tabulation CONDITIONS POWER LOSS VIN 12 V VOUT 3.9 V IOUT 1A VD1 0.45 V RDS(ON) 300 m PCOND 108 mW PSW 288 mW fSW 1.6 MHz TRISE 18 ns TFALL 12 ns IQ 1.8 mA PQ 22 mW QG 1.4 nC PG 27 mW D is calculated to be 0.36 18 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 ( PCOND + PSW + PQ + PG ) = PINTERNAL PINTERNAL = 445mW (27) (28) 8.2 Typical Applications 8.2.1 VBOOST Derived from VIN (VIN = 5 V, IF = 1 A) D2 VIN BOOST VIN C3 C1 L1 VOUT SW LM3405A D1 DC or PWM C2 C4 EN/DIM IF LED1 FB GND R1 Copyright (c) 2016, Texas Instruments Incorporated Figure 23. VBOOST Derived from VIN (VIN = 5 V, IF = 1 A) Diagram 8.2.1.1 Design Requirements * * * * * * Input Voltage: VIN = 5 V 10% LED Current: IF = 1 A LED Forward Voltage: VLED = 3.4 V Output Voltage: VOUT = 3.4 V + 0.2 V = 3.6 V Ripple Ratio: r < 0.6 PWM Dimmable 8.2.1.2 Detailed Design Procedure 8.2.1.2.1 Calculate Duty Cycle (D) Calculate the nominal duty cycle for calculations and ensure the maximum duty cycle will not be exceeded in the application using Equation 29: D= VOUT 3.6V = = 0.72 5V VIN (29) Using the same equation DMAX can be calculated for the minimum input voltage of 4.5 V. The duty cycle at 4.5 V is 0.8 which is less than the minimum DMAX of 0.85 specified in Electrical Characteristics. 8.2.1.2.2 Choose Capacitor Values (C1, C2, C3, and C4) Low input voltage applications and PWM dimming applications generally require more input capacitance so the higher value of C1 = 10 F is chosen for best performance. The other capacitor values chosen are the recommended values of C2 = C4 = 1 F and C3 = 0.01 F. All capacitors chosen are X5R or X7R dielectric ceramic capacitors of sufficient voltage rating. 8.2.1.2.3 Set the Nominal LED Current (R1) The nominal LED current at 100% PWM dimming duty cycle is set by the resistor R1. R1 can be calculated using Equation 30: R1 = VFB 0.205V = = 0.205 1A IF (30) Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 19 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com Typical Applications (continued) The standard value of R1 = 0.2 is chosen. R1 should have a power rating of at least 1/4 W. 8.2.1.2.4 Choose Diodes (D1 and D2) For the boost diode, D2, choose a low current diode with a voltage rating greater than the input voltage to give some margin. D2 should also be a schottky to minimize the forward voltage drop. For this example a schottky diode of D2 = 100 mA, 30 V is chosen. The catch diode, D1, should be a schottky diode and should have a voltage rating greater than the input voltage and a current rating greater than the average current. The average current in D1 can be calculated with Equation 31: ID1 = IF x :1 - D; = 1A x :1 - 0.72; = 0.28A (31) For this example D1 = 1 A, 10 V is chosen. 8.2.1.2.5 Calculate the Inductor Value (L1) The inductor value is chosen for a given ripple ratio (r). To calculate L1 the forward voltage of D1 is required. In this case the chosen diode has a forward voltage drop of VF = 0.37 V. Given the desired ripple ratio L1 is calculated as: L= VOUT + VD1 3.6V + 0.37V = = 4.1 IF x r x fSW 1A x 0.6 x 1.6MHz H (32) The next larger standard value of L1 = 4.7 H is chosen. A ripple ratio of 0.6 translates to a iL of 600 mA and a peak inductor current of 1.3 A (IF + iL/2). Choose an inductor with a saturation current rating of greater than 1.3 A. Table 3. Bill of Materials for Figure 23 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A LED Driver LM3405A Texas Instruments C1, Input Cap 10 F, 6.3 V, X5R C3216X5R0J106M TDK C2, Output Cap 1 F, 10 V, X7R GRM319R71A105KC01D Murata C3, Boost Cap 0.01 F, 16 V, X7R 0805YC103KAT2A AVX C4, Feedforward Cap 1 F, 10 V, X7R GRM319R71A105KC01D Murata D1, Catch Diode Schottky, 0.37 V at 1A, VR = 10 V MBRM110LT1G ON Semiconductor D2, Boost Diode Schottky, 0.36 V at 15 mA CMDSH-3 Central Semiconductor L1 4.7 H, 1.6 A SLF6028T-4R7M1R6 TDK R1 0.2 , 0.5 W, 1% WSL2010R2000FEA Vishay LED1 1.5 A, White LED LXK2-PW14 Lumileds 8.2.1.3 Application Curve Figure 24. Efficiency vs Input Voltage 20 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 8.3 System Examples 8.3.1 VBOOST Derived from VOUT (VIN = 12 V, IF = 1 A) D2 VIN BOOST VIN C3 C1 L1 VOUT SW LM3405A C2 D1 DC or PWM C4 EN/DIM IF LED1 FB GND R1 Copyright (c) 2016, Texas Instruments Incorporated Figure 25. VBOOST Derived from VOUT (VIN = 12 V, IF = 1 A) Diagram Table 4. Bill of Materials for Figure 25 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A LED Driver LM3405A Texas Instruments C1, Input Cap 10 F, 25 V, X5R ECJ-3YB1E106K Panasonic C2, Output Cap 1 F, 10 V, X7R GRM319R71A105KC01D Murata C3, Boost Cap 0.01 F, 16 V, X7R 0805YC103KAT2A AVX C4, Feedforward Cap 1 F, 10 V, X7R GRM319R71A105KC01D Murata D1, Catch Diode Schottky, 0.5 V at 1 A, VR = 30 V SS13 Vishay D2, Boost Diode Schottky, 0.36 V at 15 mA CMDSH-3 Central Semiconductor L1 4.7 H, 1.6 A SLF6028T-4R7M1R6 TDK R1 0.2 , 0.5 W, 1% WSL2010R2000FEA Vishay LED1 1.5 A, White LED LXK2-PW14 Lumileds 8.3.2 VBOOST Derived from VIN through a Series Zener Diode (D3) (VIN = 15 V, IF = 1 A) D3 D2 BOOST VIN VIN C3 C1 L1 VOUT SW LM3405A DC or PWM D1 C2 C4 EN/DIM IF LED1 FB GND R1 Copyright (c) 2016, Texas Instruments Incorporated Figure 26. VBOOST Derived from VIN through a Series Zener Diode (D3) (VIN = 15 V, IF = 1 A) Diagram Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 21 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com Table 5. Bill of Materials for Figure 26 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A LED Driver LM3405A Texas Instruments C1, Input Cap 10 F, 25 V, X5R ECJ-3YB1E106K Panasonic C2, Output Cap 1 F, 10 V, X7R GRM319R71A105KC01D Murata C3, Boost Cap 0.01 F, 16 V, X7R 0805YC103KAT2A AVX C4, Feedforward Cap 1 F, 10 V, X7R GRM319R71A105KC01D Murata D1, Catch Diode Schottky, 0.5 V at 1A, VR = 30 V SS13 Vishay D2, Boost Diode Schottky, 0.36 V at 15 mA CMDSH-3 Central Semiconductor D3, Zener Diode 11 V, 350 mW, SOT-23 BZX84C11 Fairchild L1 6.8 H, 1.5 A SLF6028T-6R8M1R5 TDK R1 0.2 , 0.5 W, 1% WSL2010R2000FEA Vishay LED1 1.5 A, White LED LXK2-PW14 Lumileds 8.3.3 VBOOST Derived from VIN through a Shunt Zener Diode (D3) (VIN = 18 V, IF = 1 A) C5 D3 R2 D2 VIN BOOST VIN C3 C1 L1 VOUT SW LM3405A D1 C2 C4 DC or PWM IF LED1 EN/DIM FB GND R1 Copyright (c) 2016, Texas Instruments Incorporated Figure 27. VBOOST Derived From VIN Through a Shunt Zener Diode (D3) (VIN = 18 V, IF = 1 A) Diagram Table 6. Bill of Materials for Figure 27 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A LED Driver LM3405A Texas Instruments C1, Input Cap 10 F, 25 V, X5R ECJ-3YB1E106K Panasonic C2, Output Cap 1 F, 10 V, X7R GRM319R71A105KC01D Murata C3, Boost Cap 0.01 F, 16 V, X7R 0805YC103KAT2A AVX C4, Feedforward Cap 1 F, 10 V, X7R GRM319R71A105KC01D Murata C5, Shunt Cap 0.1 F, 16 V, X7R GRM219R71C104KA01D Murata D1, Catch Diode Schottky, 0.5 V at 1 A, VR = 30 V SS13 Vishay D2, Boost Diode Schottky, 0.36 V at 15 mA CMDSH-3 Central Semiconductor D3, Zener Diode 4.7 V, 35 0mW, SOT-23 BZX84C4 V7 Fairchild L1 6.8 H, 1.5 A SLF6028T-6R8M1R5 TDK R1 0.2 , 0.5 W, 1% WSL2010R2000FEA Vishay R2 1.91 k, 1% CRCW08051K91FKEA Vishay LED1 1.5 A, White LED LXK2-PW14 Lumileds 22 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 8.3.4 LED MR16 Lamp Application (VIN = 12-V AC, IF = 0.75 A) Copyright (c) 2016, Texas Instruments Incorporated Figure 28. LED MR16 Lamp Application (VIN = 12-V AC, IF = 0.75 A) Diagram Table 7. Bill of Materials for Figure 28 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A LED Driver LM3405A Texas Instruments C1, Input Cap 10 F, 25 V, X5R ECJ-3YB1E106K Panasonic C2, Output Cap 1 F, 10 V, X7R GRM319R71A105KC01D Murata C3, Boost Cap 0.01 F, 16 V, X7R 0805YC103KAT2A AVX C5, Input Cap 220 F, 25 V, electrolytic ECE-A1EN221U Panasonic D1, Catch Diode Schottky, 0.5 V at 1 A, VR = 30 V SS13 Vishay D2, Boost Diode Schottky, 0.36 V at 15 mA CMDSH-3 Central Semiconductor D3, Rectifier Diode Schottky, 0.385 V at 500 mA CMHSH5-2L Central Semiconductor D4, Rectifier Diode Schottky, 0.385 V at 500 mA CMHSH5-2L Central Semiconductor D5, Rectifier Diode Schottky, 0.385 V at 500 mA CMHSH5-2L Central Semiconductor D6, Rectifier Diode Schottky, 0.385 V at 500 mA CMHSH5-2L Central Semiconductor L1 6.8 H, 1.5 A SLF6028T-6R8M1R5 TDK R1 0.27 , 0.33 W, 1% ERJ8BQFR27 Panasonic LED1 1 A, White LED LXHL-PW09 Lumileds 8.3.5 VBOOST Derived from VOUT through a Series Zener Diode (D3) ( VIN = 18 V, IF = 1 A ) D3 D2 VIN BOOST VIN C3 C1 L1 VOUT SW LM3405A D1 DC or PWM C2 LED1 IF C4 EN/DIM LED2 FB GND R1 Copyright (c) 2016, Texas Instruments Incorporated Figure 29. VBOOST Derived from VOUT Through a Series Zener Diode (D3) ( VIN = 18 V, IF = 1 A) Diagram Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 23 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com Table 8. Bill of Materials for Figure 29 PART ID PART VALUE PART NUMBER MANUFACTURER U1 1-A LED Driver LM3405A Texas Instruments C1, Input Cap 10 F, 25 V, X5R ECJ-3YB1E106K Panasonic C2, Output Cap 1 F, 16 V, X7R GRM319R71A105KC01D Murata C3, Boost Cap 0.01 F, 16 V, X7R 0805YC103KAT2A AVX C4, Feedforward Cap 1 F, 16 V, X7R GRM319R71A105KC01D Murata D1, Catch Diode Schottky, 0.5 V at 1 A, VR = 30 V SS13 Vishay D2, Boost Diode Schottky, 0.36 V at 15 mA CMDSH-3 Central Semiconductor D3, Zener Diode 3.6 V, 350 mW, SOT-23 BZX84C3V6 Fairchild L1 6.8 H, 1.5 A SLF6028T-6R8M1R5 TDK R1 0.2 , 0.5 W, 1% WSL2010R2000FEA Vishay LED1 1.5 A, White LED LXK2-PW14 Lumileds LED2 1.5 A, White LED LXK2-PW14 Lumileds 24 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A LM3405A www.ti.com SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 9 Power Supply Recommendations Any DC output power supply may be used provided it has a high enough voltage and current rating required for the particular application. 10 Layout 10.1 Layout Guidelines When planning the layout there are a few things to consider when trying to achieve a clean, regulated output. The most important consideration when completing the layout is the close coupling of the GND connections of the input capacitor C1 and the catch diode D1. These ground ends should be close to one another and be connected to the GND plane with at least two vias. Place these components as close to the IC as possible. The next consideration is the location of the GND connection of the output capacitor C2, which should be near the GND connections of C1 and D1. There should be a continuous ground plane on the bottom layer of a two-layer board. The FB pin is a high impedance node and care should be taken to make the FB trace short to avoid noise pickup that causes inaccurate regulation. The LED current setting resistor R1 should be placed as close as possible to the IC, with the GND of R1 placed as close as possible to the GND of the IC. The VOUT trace to LED anode should be routed away from the inductor and any other traces that are switching. High AC currents flow through the VIN, SW and VOUT traces, so they should be as short and wide as possible. Radiated noise can be decreased by choosing a shielded inductor. The remaining components should also be placed as close as possible to the IC. See AN-1229 SIMPLE SWITCHER(R) PCB Layout Guidelines (SNVA054) for further considerations and the LM3405A demo board as an example of a four-layer layout. 10.2 Layout Example GND FB EN/DIM LED- GND GND NC VIN BOOST SW VIN LED+ GND THERMAL/POWER VIA SIGNAL VIA Figure 30. Layout Example (MSOP-PowerPAD Package, Schematic in Figure 23) Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A 25 LM3405A SNVS508D - OCTOBER 2007 - REVISED SEPTEMBER 2016 www.ti.com 11 Device and Documentation Support 11.1 Documentation Support 11.1.1 Related Documentation For related documentation see the following: * AN-1229 SIMPLE SWITCHER(R) PCB Layout Guidelines (SNVA054) * AN-1644 Powering and Dimming High-Brightness LEDs with the LM3405 Constant-Current Buck Regulator (SNVA247) * AN-1656 Design Challenges of Switching LED Drivers (SNVA253) * AN-1685 LM3405A Demo Board (SNVA271) * AN-1899 LM3405A VSSOP Evaluation Board (SNVA370) * AN-1982 Small, Wide Input Voltage Range LM2842 Keeps LEDs Cool (SNVA402) * LM3405A Reference Design for MR16 LED Bulb, 600mA (SNVU101) 11.2 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 11.3 Community Resource The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2ETM Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 11.4 Trademarks PowerPAD, E2E are trademarks of Texas Instruments. SIMPLE SWITCHER is a registered trademark of Texas Instruments. All other trademarks are the property of their respective owners. 11.5 Electrostatic Discharge Caution 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. 11.6 Glossary SLYZ022 -- TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. 26 Submit Documentation Feedback Copyright (c) 2007-2016, Texas Instruments Incorporated Product Folder Links: LM3405A PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (C) Device Marking (3) (4/5) (6) LM3405AXMK/NOPB ACTIVE SOT-23-THIN DDC 6 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SSEB LM3405AXMKE/NOPB ACTIVE SOT-23-THIN DDC 6 250 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SSEB LM3405AXMKX/NOPB ACTIVE SOT-23-THIN DDC 6 3000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SSEB LM3405AXMY/NOPB ACTIVE HVSSOP DGN 8 1000 RoHS & Green SN Level-1-260C-UNLIM SVSA LM3405AXMYX/NOPB ACTIVE HVSSOP DGN 8 3500 RoHS & Green SN Level-1-260C-UNLIM SVSA (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) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device 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 Device Marking for that device. (6) Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two lines if the finish value exceeds the maximum column width. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 10-Dec-2020 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 2 PACKAGE MATERIALS INFORMATION www.ti.com 6-Sep-2019 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) LM3405AXMK/NOPB SOT23-THIN DDC 6 1000 178.0 8.4 LM3405AXMKE/NOPB SOT23-THIN DDC 6 250 178.0 LM3405AXMKX/NOPB SOT23-THIN DDC 6 3000 LM3405AXMY/NOPB HVSSOP DGN 8 LM3405AXMYX/NOPB HVSSOP DGN 8 3.2 3.2 1.4 4.0 8.0 Q3 8.4 3.2 3.2 1.4 4.0 8.0 Q3 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1 3500 330.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1 Pack Materials-Page 1 W Pin1 (mm) Quadrant PACKAGE MATERIALS INFORMATION www.ti.com 6-Sep-2019 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM3405AXMK/NOPB SOT-23-THIN DDC 6 1000 210.0 185.0 35.0 LM3405AXMKE/NOPB SOT-23-THIN DDC 6 250 210.0 185.0 35.0 LM3405AXMKX/NOPB SOT-23-THIN DDC 6 3000 210.0 185.0 35.0 LM3405AXMY/NOPB HVSSOP DGN 8 1000 210.0 185.0 35.0 LM3405AXMYX/NOPB HVSSOP DGN 8 3500 367.0 367.0 35.0 Pack Materials-Page 2 PACKAGE OUTLINE DDC0006A SOT - 1.1 max height SCALE 4.000 SOT 3.05 2.55 1.75 1.45 PIN 1 INDEX AREA 1.100 0.847 B 1 0.1 C A 6 4X 0.95 3.05 2.75 1.9 4 3 0.5 0.3 0.2 0.1 TYP 0.0 6X C 0 -8 TYP 0.20 TYP 0.12 C A B SEATING PLANE 0.6 TYP 0.3 0.25 GAGE PLANE 4214841/B 11/2020 NOTES: 1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing per ASME Y14.5M. 2. This drawing is subject to change without notice. 3. Reference JEDEC MO-193. www.ti.com EXAMPLE BOARD LAYOUT DDC0006A SOT - 1.1 max height SOT SYMM 6X (1.1) 1 6 6X (0.6) SYMM 4X (0.95) 4 3 (R0.05) TYP (2.7) LAND PATTERN EXAMPLE EXPLOSED METAL SHOWN SCALE:15X SOLDER MASK OPENING METAL UNDER SOLDER MASK METAL SOLDER MASK OPENING EXPOSED METAL EXPOSED METAL 0.07 MIN ARROUND 0.07 MAX ARROUND NON SOLDER MASK DEFINED SOLDER MASK DEFINED SOLDERMASK DETAILS 4214841/B 11/2020 NOTES: (continued) 4. Publication IPC-7351 may have alternate designs. 5. Solder mask tolerances between and around signal pads can vary based on board fabrication site. www.ti.com EXAMPLE STENCIL DESIGN DDC0006A SOT - 1.1 max height SOT SYMM 6X (1.1) 1 6 6X (0.6) SYMM 4X(0.95) 4 3 (R0.05) TYP (2.7) SOLDER PASTE EXAMPLE BASED ON 0.125 THICK STENCIL SCALE:15X 4214841/B 11/2020 NOTES: (continued) 6. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate design recommendations. 7. Board assembly site may have different recommendations for stencil design. www.ti.com PACKAGE OUTLINE TM DGN0008A PowerPAD VSSOP - 1.1 mm max height SCALE 4.000 SMALL OUTLINE PACKAGE C 5.05 TYP 4.75 A 0.1 C SEATING PLANE PIN 1 INDEX AREA 6X 0.65 8 1 2X 3.1 2.9 NOTE 3 1.95 4 5 8X B 3.1 2.9 NOTE 4 0.38 0.25 0.13 C A B 0.23 0.13 SEE DETAIL A EXPOSED THERMAL PAD 4 5 0.25 GAGE PLANE 2.0 1.7 9 1.1 MAX 8 1 0 -8 0.15 0.05 0.7 0.4 DETAIL A A 20 1.88 1.58 TYPICAL 4218836/A 11/2019 PowerPAD is a trademark of Texas Instruments. NOTES: 1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing per ASME Y14.5M. 2. This drawing is subject to change without notice. 3. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not exceed 0.15 mm per side. 4. This dimension does not include interlead flash. Interlead flash shall not exceed 0.25 mm per side. 5. Reference JEDEC registration MO-187. www.ti.com EXAMPLE BOARD LAYOUT TM DGN0008A PowerPAD VSSOP - 1.1 mm max height SMALL OUTLINE PACKAGE (2) NOTE 9 METAL COVERED BY SOLDER MASK (1.88) SOLDER MASK DEFINED PAD SYMM 8X (1.4) (R0.05) TYP 8 8X (0.45) 1 (3) NOTE 9 SYMM 9 (2) (1.22) 6X (0.65) 5 4 ( 0.2) TYP VIA (0.55) SEE DETAILS (4.4) LAND PATTERN EXAMPLE EXPOSED METAL SHOWN SCALE: 15X SOLDER MASK OPENING METAL UNDER SOLDER MASK METAL SOLDER MASK OPENING EXPOSED METAL EXPOSED METAL 0.05 MAX ALL AROUND NON-SOLDER MASK DEFINED (PREFERRED) 0.05 MIN ALL AROUND SOLDER MASK DEFINED SOLDER MASK DETAILS 15.000 4218836/A 11/2019 NOTES: (continued) 6. Publication IPC-7351 may have alternate designs. 7. Solder mask tolerances between and around signal pads can vary based on board fabrication site. 8. Vias are optional depending on application, refer to device data sheet. If any vias are implemented, refer to their locations shown on this view. It is recommended that vias under paste be filled, plugged or tented. 9. Size of metal pad may vary due to creepage requirement. www.ti.com EXAMPLE STENCIL DESIGN TM DGN0008A PowerPAD VSSOP - 1.1 mm max height SMALL OUTLINE PACKAGE (1.88) BASED ON 0.125 THICK STENCIL SYMM (R0.05) TYP 8X (1.4) 8X (0.45) 8 1 SYMM (2) BASED ON 0.125 THICK STENCIL 6X (0.65) 5 4 METAL COVERED BY SOLDER MASK (4.4) SEE TABLE FOR DIFFERENT OPENINGS FOR OTHER STENCIL THICKNESSES SOLDER PASTE EXAMPLE EXPOSED PAD 9: 100% PRINTED SOLDER COVERAGE BY AREA SCALE: 15X STENCIL THICKNESS SOLDER STENCIL OPENING 0.1 0.125 0.15 0.175 2.10 X 2.24 1.88 X 2.00 (SHOWN) 1.72 X 1.83 1.59 X 1.69 4218836/A 11/2019 NOTES: (continued) 10. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate design recommendations. 11. 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