LM3402EVAL/NOPB

User's Guide SNVA175C – September 2006 – Revised April 2013 AN-1500 LM3402/02HV Demo Board 1 Introduction The LM3402/LM3402HV is a buck regulator derived controlled current source designed to drive a series string of high power, high brightness LEDs (HBLEDs) such as the Luxeon™ I Emitter at forward currents of up to 500 mA. The board can accept an input voltage ranging from 6V to 42V when using the LM3402. When using the pin-for-pin compatible LM3402HV the upper bound of input voltage is 75V. The converter output voltage adjusts as needed to maintain a constant current through the LED array. The LM3402/02HV is a true step-down regulator with an output voltage range extending from a VO(MIN) of 200 mV (the reference voltage) to a VO(MAX) determined by the minimum off time (typically 300 ns). It can maintain regulated current through any number of LEDs as long as the combined forward voltage of the array does not exceed VO(MAX).. 2 Circuit Performance LM3402 The LM3402 circuit and BOM have been designed to provide a constant forward current of 350 mA to a single LED with a forward voltage of approximately 3.5V. (Typical of white, blue, and green LEDs using InGaN technology.) When powered from a 24V ±5% input the demo board will maintain the average LED current, IF, to within 10% of 350 mA. The ripple current, ΔiF, will not exceed 70 mA peak-to-peak. Switching frequency for the demo board is 600 kHz ± 10% over the input voltage range of 6V to 42V. 3 Circuit Performance LM3402HV The LM3402HV circuit and BOM have been designed to provide a constant forward current of 350 mA to a single LED with a forward voltage of approximately 3.5V. When powered from a 48V ± 5% input the demo board will maintain IF to within ±5% of 350 mA. Ripple current will not exceed 70 mA peak-to-peak. Switching frequency for the demo board is 250 kHz ±10% over the input voltage range of 6V to 75V. 4 Connecting to LED Array The LM3402/02HV demo board includes a female 6-pin SIP, J1, connector as well as two standard 94mil turret connectors for the cathode and anode connections of the LED array. Figure 1 shows the pinout of J1. Solid, 18 or 20 gauge wire with about 1 cm of insulation stripped away makes a convenient, solderless connection to J1. P6 Cathode of Last LED C535676 Connector P1 Anode of First LED Figure 1. Connecting to LED Array All trademarks are the property of their respective owners. SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1500 LM3402/02HV Demo Board 1 Setting the LED Current 5 www.ti.com Setting the LED Current The default forward current ILED delivered to the LED array is 350 mA, typical of many 1W LEDs. To adjust this value the current setting resistor RSNS can be changed according to the following equation: 0.2 x L RSNS = IF x L + VO x tSNS - VIN - VO x tON 2 (1) tSNS = 220 ns (2) This resistor should be rated to handle the power dissipation of the LED current. For example, the closest 5% tolerance resistor to set an LED current of 350 mA is 0.56 Ω. In steady state this resistor will dissipate (0.352 × 0.56) = 69 mW, indicating that a resistor with a 1/8W power rating is appropriate. 6 PWM Dimming The DIM1 terminal on the PCB provides an input for a pulse width modulation signal for dimming of the LED array. In order to fully enable and disable the LM3402/02HV the PWM signal should have a maximum logic low level of 0.8V and a minimum logic high level of 2.2V. The maximum PWM dimming frequency, minimum PWM duty cycle and maximum duty cycle are illustrated in Figure 2. PWM frequency should be at least one order of magnitude below the LM3402/02HV switching frequency. The interval tD represents the delay from a logic high at the DIM pin to the onset of the output current. The quantities tSU and tSD represent the time needed for the output current to slew up to steady state and slew down to zero, respectively. Typical response times for the standard LM3402 and LM3402HV demo boards circuits are shown in Section 11. T T T DIM D tD DMIN tSD tSU tD tSU DMAX tSD tD tSU tSD IF T= 1 fPWM DMIN = T + tSD tD + tSU DMAX = T T Figure 2. PWM Dimming Limits The logic of DIM1 is direct, hence the LM3402/02HV will deliver regulated output current when the voltage at DIM1 is high, and the current output is disabled when the voltage at DIM1 is low. Connecting a constant logic low will disable the output, and the LM3402/02HV is enabled if the DIM pin is open-circuited. The DIM1 function disables only the power NFET, leaving all other circuit blocks functioning to minimize the converter response time. 2 AN-1500 LM3402/02HV Demo Board SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Low Power Shutdown www.ti.com The DIM2 terminal provides a second method for PWM dimming by connecting to the gate of an optional NFET, Q1. Note that Q1 is not provided on the standard BOM, and must be added for the DIM2 function to operate. Q1 provides a parallel path for the LED current. This small NFET can be turned on and off much more quickly than the LM3402/02HV can shutdown the internal NFET, providing faster response time for higher frequency and/or greater resolution in the PWM dimming signal. The tradeoff in this method is that the full current flows through Q1 while the LED is off, resulting in lower efficiency. The logic of DIM2 is inverted, hence the LM3402/02HV will deliver regulated output current when the voltage at DIM2 is low, and the current output is disabled when the voltage at DIM2 is high. Connecting a constant logic high to the DIM2 will turn off the LED but will not shut down the LM3402/02HV. 7 Low Power Shutdown The LM3402/02HV can be placed into a low power shutdown (typically 90 µA) by grounding the OFF terminal. During normal operation this terminal should be left open-circuit. 8 Output Open Circuit With either DIM terminal floating or connected to logic high, the LM3402/02HV will begin to operate as soon as it has an input of at least 6V. In the case that the input is powered but no LED array is connected the output voltage will rise to equal the input voltage. The output of the circuit is rated to 50V (LM3402) or 100V (LM3402HV) and will not suffer damage, however care should be taken not to connect an LED array if the output voltage is higher than the target forward voltage of the LED array in steady state. Alternatively, a zener diode and zener current limiting resistor can be placed in the positions Z1 and RZ. In the case of an accidental open circuit at the output Z1 will enter reverse bias and attempt to pull the CS pin voltage up to the output voltage. An internal comparator monitors the CS pin voltage and will disable the internal NFET in this case. The result is a low power hiccup mode, designed to prevent excessive voltage at the output and thermal stress on the inductor, internal NFET, and input voltage source. VIN = 6V to 42V (LM3402) VIN = 6V to 75V (LM3402HV) CIN 2 8 VIN BOOT CB L1 SW 1 LED ANODE RON 6 D1 RON CO1 (used in BOM 2 only) LM3402/02HV CS OFF DIM1 3 DIM GND 4 VCC 5 LED CATHODE RSNS 7 CF Figure 3. Standard Schematic SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1500 LM3402/02HV Demo Board 3 Bill of Materials 9 www.ti.com Bill of Materials Table 1. Bill of Materials (LM3402) ID Part Number Type Size Parameters Qty Vendor U1 LM3402 LED Driver VSSOP-8 42V, 0.5A 1 Texas Instruments L1 SLF10145T-101M1R0 Inductor 10.1 × 10.1 × 4.5mm 100µH, 1A, 0.2Ω 1 TDK D1 CMSH1-60M Schottky Diode SMA 60V, 1A 1 Central Semi Cf VJ0805Y104KXXAT Capacitor 0805 100nF 10% 1 Vishay Cb VJ0805Y103KXXAT Capacitor 0805 10nF 10% 1 Vishay Cin C3216X7R1H105M Capacitor 1206 1µF 50V 1 TDK Rsns ERJ6BQFR56V Resistor 0805 0.56Ω 1% 1 Panasonic Ron CRCW08054642F Resistor 0805 46.4kΩ 1% 1 Vishay Rz CRCW08050R00F Resistor 0805 0Ω 1 Vishay DIM1, DIM2 160-1512 Terminal Silver 0.062” 2 Cambion GND1, GND2, GND3, VIN, ISNS / C, Vo / A, SW 160-1026 Terminal Silver 0.094” 7 Cambion J1 535676-5 Connector Custom 1 Tyco/AMP 6 Pins Table 2. Bill of Materials (LM3402HV) 4 ID Part Number Type Size Parameters Qty Vendor U1 LM3402HV LED Driver VSSOP-8 75V, 0.5A 1 Texas Instruments L1 SLF10145T-151MR79 Inductor 10.1 × 10.1 × 4.5mm 150µH, 0.8A, 0.2Ω 1 TDK D1 CMSH1-100M Schottky Diode SMA 100V, 1A 1 Central Semi Cf VJ0805Y104KXXAT Capacitor 0805 100nF 10% 1 Vishay Cb VJ0805Y103KXXAT Capacitor 0805 10nF 10% 1 Vishay Cin C3225X7R2A105M Capacitor 1210 1µF 100V 1 TDK Co1 C3216X7R1E225M Capacitor 1206 2.2µF 25V 1 TDK Rsns ERJ6BQFR68V Resistor 0805 0.68Ω 1% 1 Panasonic Ron CRCW08051303F Resistor 0805 130kΩ 1% 1 Vishay 0Ω Rz CRCW08050R00F Resistor 0805 1 Vishay DIM1, DIM2 160-1512 Terminal Silver 0.062” 2 Cambion GND1, GND2, GND3, VIN, ISNS / C, Vo / A, SW 160-1026 Terminal Silver 0.094” 7 Cambion J1 535676-5 Connector Custom 1 Tyco/AMP AN-1500 LM3402/02HV Demo Board 6 Pins SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Evaluation Board Schematic www.ti.com 10 Evaluation Board Schematic VIN = 6V to 42V (LM3402) VIN = 6V to 75V (LM3402HV) CIN 2 8 VIN BOOT CB L1 SW 1 LED ANODE RSNB RON 6 D1 RON CSNB LM3402/02HV CS OFF DIM1 3 DIM GND 4 VCC RESR Z1 CO1 Q1 CO2 RPD RZ 5 DIM2 RSNS 7 LED CATHODE CF Figure 4. Complete Evaluation Board Schematic SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1500 LM3402/02HV Demo Board 5 Typical Performance Characteristics 11 6 www.ti.com Typical Performance Characteristics Efficiency for Table 1 TA = 25°C, IF = 350 mA Efficiency for Table 2 TA = 25°C, IF = 350 mA IF vs VIN for Table 1 TA = 25°C IF vs VIN for Table 2 TA = 25°C AN-1500 LM3402/02HV Demo Board SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Typical Performance Characteristics www.ti.com DIM Pin Enable Table 1 DIM 5V/DIV DIM Pin Disable Table 1 5V/DIV DIM 100 mA/DIV 100 mA/DIV IF IF 2 és/DIV 1 és/DIV Switching Waveforms for Table 1 Output Ripple Current Table 1 100 mA/DIV IF IF SW 10 mA/DIV 10V/DIV 1 és/DIV 1 és/DIV DIM Pin Enable Table 2 DIM 5V/DIV DIM Pin Disable Table 2 5V/DIV DIM 100 mA/DIV 100 mA/DIV IF IF 4 és/DIV SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated 10 és/DIV AN-1500 LM3402/02HV Demo Board 7 Typical Performance Characteristics www.ti.com Switching Waveforms for Table 2 Output Ripple Current Table 2 100 mA/DIV IF IF SW 5 mA/DIV 20V/DIV 2 és/DIV 2 és/DIV 8 AN-1500 LM3402/02HV Demo Board SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Layout www.ti.com 12 Layout Figure 5. Top Layer and Top Overlay SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated AN-1500 LM3402/02HV Demo Board 9 Layout www.ti.com Figure 6. Bottom Layer and Bottom Overlay 10 AN-1500 LM3402/02HV Demo Board SNVA175C – September 2006 – Revised April 2013 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated 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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