LM3433SQ-36AEV/NOPB

User's Guide SNVA386D – March 2009 – Revised May 2013 AN-1937 LM3433 10A to 40A LED Driver Evaluation Board 1 Introduction The LM3433 is an adaptive constant on-time DC/DC buck constant current controller designed to drive a high brightness LED (HB LED) at high forward currents. It is a true current source that provides a constant current with constant ripple current regardless of the LED forward voltage drop. The board can accept an input voltage ranging from -9V to -14V with respect to GND. The output configuration allows the anodes of multiple LEDs to be tied directly to the ground referenced chassis for maximum heat sink efficacy when a negative input voltage is used. 2 LM3433 High Current Board Description The evaluation board is designed to provide a constant current in the range of 10A to 60A (although the board is thermally limited to approximately 40A continuous operation) and can connect directly to a Luminus Devices, Inc. PhlatLight® PT-120 or similar high current LED. It is ideal for pulsing an LED at 30A or greater for applications such as rear and forward projection. The LM3433 requires two input voltages for operation. A positive voltage with respect to GND is required for the bias and control circuitry and a negative voltage with respect to GND is required for the main power input. This allows for the capability of using common anode LEDs so that the anodes can be tied to the ground referenced chassis. The evaluation board only requires one input voltage of -12V with respect to GND (any high current 12V supply will work). The positive voltage with respect to GND on the board is supplied by the LM5002 circuit (see below). Initially the output current is set at the minimum of approximately 10A with the POT P1 fully counter-clockwise. To set the desired current level a short may be connected between LED+ and LED-, then use a current probe and turn the POT clockwise until the desired current is reached. PWM dimming FETs are included on-board for testing when the LED can be connected directly next to the board. A shutdown test post on J2, ENA, is included so that startup and shutdown functions can be tested using an external voltage. Note that the test points for GND and -12V are for measurement only, the high current input source should be connected through J1. 3 LM5002 Circuit The positive voltage with respect to GND on the board is supplied by the LM5002 circuit. The LM5002 feedback is level shifted so that the output that supplies the LM3433 bias circuitry will remain at +5V with respect to GND regardless of where VEE is in the -9V to -14V range. The LM5002 circuit also provides a UVLO function to remove the possibility of the LM3433 drawing high currents at input voltages less than 9V during startup. This circuit was designed with enough output current to power a small 5V sideblower fan (Sunon part number B0502AFB2-8) to help keep the inductor, and therefore the board to some degree, cooler if extreme ambient temperatures are expected. One LM5002 circuit can supply enough current to drive the positive voltage for multiple LM3433 circuits in a system, up to approximately 100. PowerPAD is a trademark of Texas Instruments. PhlatLight is a registered trademark of Luminus Devices, Inc. All other trademarks are the property of their respective owners. SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 1 Setting the LED Current 4 www.ti.com Setting the LED Current The LM3433 evaluation board is designed so that the LED current can be set in multiple ways. There is a shunt on J2 initially connecting the ADJ pin to the POT allowing the current to be adjusted using the POT P1. This POT will apply a voltage to the ADJ pin between 0.3V and 1.5V with respect to GND to adjust the voltage across the sense resistor (RSENSE) R15. The shunt may also be removed and an external voltage positive with respect to GND can then be applied to the ADJ test point on the board. A 2mΩ resistor comes mounted on the board (five 10mΩ resistors in parallel) so using the VSENSE vs. VADJ graph in the Section 8 the current can be set using the following equation: ILED = VSENSE/RSENSE (1) Alternatively the shunt can be removed and the ADJ test point can be connected to the VINX test point to fix VSENSE at 60mV for 30A output current. 5 PWM Dimming The LM3433 is capable of high speed PWM dimming in excess of 40kHz. Dimming is accomplished by shorting across the LED with a FET(s). Dimming FETs are included on the evaluation board for testing LEDs placed close to the board. The FETs on the evaluation board should be removed if using dimming FETs remotely placed close to the LED (STRONGLY recommended). If the FETs cannot be placed directly next to the LED then some form of snubber may be required to prevent damage to the LM3433, LM5111, and LM2937 due to the large spikes caused by inductance between the LED and FETs. D4, C17, and R32 may be used to populate a snubber circuit. To use the dimming function apply square wave to the PWM test point on the board that has a positive voltage with respect to GND. When this pin is pulled high the dimming FET is enabled and the LED turns off. When it is pulled low the dimming FET is turned off and the LED turns on. A scope plot of PWM dimming is included in Section 8 showing 120Hz dimming at 20% duty cycle. 6 Reducing Component Count This board has been optimized to reduce losses in the power FETs and dimming FETs by using the LM5111 gate drivers to increase the gate drive current as well as the gate voltage for minimum RDS(ON). If more power dissipation and/or lower efficiency can be tolerated when PWM dimming then some components may be removed. As shipped an LM5111 is used to drive the PWM FET gates. The LM5111 is powered by using D6 and C25 to form a charge pump to generate a positive voltage above GND that is approximately equal to |VEE|. This voltage is then regulated down to 12V above LED- with the LM2937 to power the LM5111. The result is high gate drive current capability and a high gate voltage for the dimming FETs. With the use of the LM5111s on the main power FETs the LM3433 has enough internal drive current capability to drive the dimming FETs without the use of external components. The RDS(ON) will increase and the switch transitions will be slower but all related components could be removed. In this case R14 should be loaded and the following components may be removed: U5, U6, R33, D6, C22, and C25. Alternatively if a high voltage gate driver is used (VCC = |VEE| + Vf where Vf if the LED forward voltage drop) then D5 and C23 may be added to power the gate driver IC directly with the charge pump and U6, D6, and C25 may be removed. 7 High Current Operation and Component Lifetime When driving high current LEDs, particularly when PWM dimming, component lifetime may become a factor. In these cases the input ripple current that the input capacitors are required to withstand can become large. At lower currents long life ceramic capacitors may be able to handle this ripple current without a problem. At higher currents more input capacitance may be required. To remain cost effective this may require putting one or more aluminum electrolytic capacitors in parallel with the ceramic input capacitors. Since the operational lifetime of LEDs is very long (up to 50,000 hours) the longevity of an aluminum electrolytic capacitor can become the main factor in the overall system lifetime. The first consideration for selecting the input capacitors is the RMS ripple current they will be required to handle. This current is given by the following equation: IRMS = ILED 2 VLED(|VEE|-VLED) |VEE| (2) AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback High Current Operation and Component Lifetime www.ti.com The parallel combination of the ceramic and aluminum electrolytic input capacitors must be able to handle this ripple current. The aluminum electrolytic in particular should be able to handle the ripple current without a significant rise in core temperature. A good rule of thumb is that if the case temperature of the capacitor is 5°C above the ambient board temperature then the capacitor is not capable of sustaining the ripple current for its full rated lifetime and a more robust or lower ESR capacitor should be selected. The other main considerations for aluminum electrolytic capacitor lifetime are the rated lifetime and the ambient operating temperature. An aluminum electrolytic capacitor comes with a lifetime rating at a given core temperature, such as 5000 hours at 105°C. As dictated by physics the capacitor lifetime should double for each 7°C below this temperature the capacitor operates at and should halve for each 7°C above this temperature the capacitor operates at. A good quality aluminum electrolytic capacitor will also have a core temperature of approximately 3°C to 5°C above the ambient temperature at rated RMS operating current. So as an example, a capacitor rated for 5,000 hours at 105°C that is operating in an ambient environment of 85°C will have a core temperature of approximately 90°C at full rated RMS operating current. In this case the expected operating lifetime of the capacitor will be approximately just over 20,000 hours. The actual lifetime (LifeACTUAL) can be found using the equation: (T CORE - TACTUAL LifeACTUAL = LifeRATED X 2 7 ) (3) Where LifeRATED is the rated lifetime at the rated core temperature TCORE. For example: If the ambient temperature is 85°C the core temperature is 85°C + 5°C = 90°C. (105°C - 90°C)/7°C = 2.143. 2^2.413 = 4.417. So the expected lifetime is 5,000*4.417 = 22,085 hours. Long life capacitors are recommended for LED applications and are available with ratings of up to 20,000 hours or more at 105°C. SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 3 High Current Operation and Component Lifetime www.ti.com Figure 1. LM3433 Evaluation Board Schematic 4 AN-1937 LM3433 10A to 40A LED Driver Evaluation Board SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback Copyright © 2009–2013, Texas Instruments Incorporated High Current Operation and Component Lifetime www.ti.com Table 1. Bill of Materials ID Part Number Type Size Qty Vendor U1 LM3433 LED Driver WQFN-24 Parameters 1 TI U2 LM5002 Boost Regulator SOIC-8 1 TI U3, U4, U5 LM5111 Gate Driver MSOPPowerPAD™-8 3 TI U6 LM2937 Linear Regulator SOT-223 1 TI C1 C0805C471K5RACTU Capacitor 0805 470pF, 50V 1 Kemet C2 LMK316BJ476ML-T Capacitor 1206 47µF, 6.3V 1 Taiyo Yuden C3a, C3b 16SH150M Capacitor MULTICAP 150µF, 16V 2 Sanyo C4a, C4b, C4c, C4d, C4e, C4f GRM32ER61C226KE20L Capacitor 1210 22µF, 16V 6 Murata C6, C34, C35 GRM32ER61C476ME15L Capacitor 1210 47µF, 16V 3 Murata C7, C8, C18 C0805C104J5RACTU Capacitor 0805 0.1µF, 50V 3 Kemet C9, C17, C23, C24, C26, C27, C29, C30 OPEN C10, C11, C20, C21, C25, C33 GRM21BR61C475KA Capacitor 0805 4.7µF, 16V 6 Murata C12 0805YD105KAT2A Capacitor 0805 1µF, 16V 1 AVX C13 C0805C103K1RACTU Capacitor 0805 10nF, 100V 1 Kemet C14 B37941K9474K60 Capacitor 0805 0.47µF, 16V 1 EPCOS Inc . C15 GRM21BF51E225ZA01L Capacitor 0805 2.2µF, 25V 1 Murata C22 GRM21BR61C106KE15 Capacitor 0805 10μF, 25V 1 Murata C18 08055C104JAT2A Capacitor 0805 0.1µF, 50V 1 AVX 0805 C28 OPEN D1, D2, D6, D7 MA2YD2600L Diode SOD-123 1210 60V, 800mA 2 Panasonic D3 MBRS240LT3 Diode SMB 40V, 2A 1 ON Semiconductor D4 OPEN SMB D5 OPEN SOD-123 J2 B8B-EH-A(LF)(SN) Connector 1 JST Sales America, Inc. J1 1761582001 Connector 1 Weidmuller J1* 1610180000 Connector Plug 1 Weidmuller J3 Molex 5114-0200 Connector Molex thermistor 1.25mm 2pos 1 Molex J4 Keystone 3547 Connector Female quickdisconnect terminal pair 2 Keystone L1 LPS3015-124ML Inductor 3015 120µH, 220mA 1 Coilcraft L2 SER2915L-332KL Inductor SER2900 3.3µH, 48A 1 Coilcraft L3, L4, L5, L6, L7, L8 HI1206T500R-10 Ferrite Bead 1206 50Ω @ 100MHz 6 Steward 100Ω @ 100MHz 1 TDK L9, L10 OPEN L11 MPZ2012S101A Ferrite Bead 1206 0805 P1 3352T-1-103LF Potentiometer BOURNS2 10kΩ 1 Bourns Q1, Q2, Q3, Q4, Q5, Q6 SIE808DF-T1-E3 FET PolarPAK 20V, 1.5mΩ 6 Vishay Dual PNP SOT363_N 1 Diodes Inc. 3 Diodes Inc. Q7 MMDT3906 -7 Q8, Q9, Q13, Q14, Q15, Q16, Q17, Q18 OPEN Q10, Q11, Q12 MMBT3904 -7 SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback SOIC-8 NPN SOT-23 AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 5 High Current Operation and Component Lifetime www.ti.com Table 1. Bill of Materials (continued) ID Part Number Type Size Parameters Qty Vendor R1 ERJ-6ENF2942V Resistor 0805 29.4kΩ 1 Panasonic R2 ERJ-6ENF2491V Resistor 0805 2.49kΩ 1 Panasonic R3, R13, R30, R31 ERJ-6ENF1002V Resistor 0805 10kΩ 4 Panasonic R4 ERJ-6GEYJ393V Resistor 0805 39kΩ 1 Panasonic R5 ERJ-6GEYJ101V Resistor 0805 100Ω 1 Panasonic R6 ERJ-6ENF1212V Resistor 0805 12.1kΩ 1 Panasonic R8 ERJ-6ENF2002V Resistor 0805 20kΩ 1 Panasonic R10 ERJ-6ENF4991V Resistor 0805 4.99kΩ 1 Panasonic R11, R12 ERJ-6ENF6192V Resistor 0805 61.9kΩ 2 Panasonic R15a, R15b, R15c, R15d, R15e WSL2512R0100FEA Resistor 2512 0.01Ω 5 Vishay R17, R18, R19, R20 ERJ-8RQF4R7V Resistor 1206 4.7Ω 4 Panasonic R24 ERJ-6GEYJ100V Resistor 0805 10Ω 1 Panasonic R25 ERJ-6ENF7502V Resistor 0805 75kΩ 1 Panasonic R33 ERJ-6ENF49R9V Resistor 1206 49.9Ω 1 Panasonic R34 ERJ-6GEYJ103V Resistor 1206 10kΩ 1 Panasonic R35 CRCW0805100KFKEA Resistor 1206 100kΩ 1 Vishay R36 CRCW080524K0FKEA Resistor 1206 24kΩ 1 Vishay R37 CRCW08056K20FKEA Resistor 1206 6.2kΩ 1 Vishay R14, R21, R22, R23, R32, R38, R39 OPEN R40, R41, R42 ERJ-6GEY0R00V Resistor 0805 0Ω 3 Panasonic -12V, GND 1502-2 Test Post TP 1502 0.109" 2 Keystone ADJ, PWM, VINX 1593-2 Test Post TP 1593 0.084" 3 Keystone 6 0805 AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback Typical Performance Characteristics www.ti.com 8 Typical Performance Characteristics 100 100 90 98 96 70 VSENSE (mV) EFFICIENCY (%) 80 94 92 60 50 40 30 90 20 88 86 -14 10 -13 -12 -11 -10 -9 0 0.2 0.4 VEE INPUT VOLTAGE (V) Figure 2. Efficiency vs. VEE Voltage (ILED = 18A, VLED = 4.3V) 0.6 0.8 1 1.2 1.4 1.6 ADJ VOLTAGE (V) Figure 3. VSENSE vs. VADJ ILED = 30A nominal, VIN = 5V, VEE = -12V Top trace: DIM input, 1V/div, DC Bottom trace: ILED, 10A/div, DC T = 2ms/div Figure 4. 120Hz PWM Dimming Waveform SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 7 Layout 9 www.ti.com Layout Figure 5. Top Layer and Top Overlay 8 AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback Layout www.ti.com Figure 6. Upper Middle Layer SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 9 Layout www.ti.com Figure 7. Lower Middle Layer 10 AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback Layout www.ti.com Figure 8. Bottom Layer and Bottom Overlay SNVA386D – March 2009 – Revised May 2013 Submit Documentation Feedback AN-1937 LM3433 10A to 40A LED Driver Evaluation Board Copyright © 2009–2013, Texas Instruments Incorporated 11 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. 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