LM3404HVEVAL/NOPB

User's Guide SNVA193E – January 2007 – Revised April 2013 AN-1545 LM3404/LM3404HV Evaluation Board 1 Introduction The LM3404/04HV 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™ K2 Emitter at forward currents of up to 1.0A. The board can accept an input voltage ranging from 6V to 42V when using the LM3404. When using the pin-for-pin compatible LM3404HV 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 LM3404/04HV 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 LM3404 The LM3404 circuit and BOM have been designed to provide a constant forward current of 1.0A to a single LED with a forward voltage of approximately 3.7V (Typical of white, blue, and green LEDs using InGaN technology) from an input of 24V ±10%. Over the input voltage range of 6V to 42V the average LED current, IF, is 1.0A ±10%, the ripple current, ΔiF, will not exceed 400 mAP-P, and the switching frequency is 450 kHz ± 10%. 3 Circuit Performance LM3404HV The LM3404HV circuit and BOM have been designed to provide a constant forward current of 1.0A to a single LED with a forward voltage of approximately 3.7V from an input of 48V ±10%. Over the input voltage range of 6V to 75V the average LED current, IF, is 1.0A ±10%, the ripple current, ΔiF, will not exceed 400 mAP-P, and the switching frequency is 200 kHz ± 10%. 4 Connecting to LED Array The LM3404/04HV Evaluation 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. SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback AN-1545 LM3404/LM3404HV Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 1 Setting the LED Current 5 www.ti.com Setting the LED Current The default forward current ILED delivered to the LED array is 1.0A, typical of many 3W 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 1.0A is 0.22 Ω. In steady state this resistor will dissipate (1.0 x 0.22) = 220 mW, indicating that a resistor with a 1/4W 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 LM3404/04HV 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 LM3404/04HV 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 LM3404 and LM3404HV demo boards circuits are shown in the Typical Performance Characteristics section. T T T DIM D tD DMIN tSD tSU tD tSU DMAX tSD tD tSU tSD IF T= 1 DMIN = fPWM T - tSD tD + tSU DMAX = T T Figure 2. PWM Dimming Limits The logic of DIM1 is direct, hence the LM3404/04HV 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 LM3404/04HV is enabled if the DIM pin is open-circuited. The DIM1 function disables only the power MOSFET, leaving all other circuit blocks functioning to minimize the converter response time. 2 AN-1545 LM3404/LM3404HV Evaluation Board SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, 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 MOSFET, 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 MOSFET can be turned on and off much more quickly than the LM3404/04HV can shutdown the internal MOSFET, providing faster response time for higher frequency and/or greater resolution in the PWM dimming signal. The trade-off 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 LM3404/04HV 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 LM3404/04HV. 7 Low Power Shutdown The LM3404/04HV 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 LM3404/04HV 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 (LM3404) or 100V (LM3404HV) 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 MOSFET 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 MOSFET, and input voltage source. VIN = 6V to 42V (LM3404) VIN = 6V to 75V (LM3404HV) CB VIN CIN BOOT L1 LED ANODE SW RON D1 RON CO1 LM3404/04HV LED CATHODE CS OFF RSNS DIM1 DIM GND VCC CF Figure 3. Standard Schematic SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback AN-1545 LM3404/LM3404HV Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 3 Bill of Materials 9 www.ti.com Bill of Materials Table 1. Bill of Materials (LM3404) ID Part Number Type Size Parameters Qty Vendor U1 LM3404 LED Driver SOIC-8 42V, 1.0A 1 Texas Instruments L1 SLF10145T- 330M1R6 Inductor 10.1 x 10.1 x 4.5mm 33µH, 1.6A, 82mΩ 1 TDK D1 CMSH2-60M Schottky Diode SMA 60V, 2A 1 Central Semi Cf VJ0805Y104KXXAT Capacitor 0805 100nF 10% 1 Vishay Cb VJ0805Y103KXXAT Capacitor 0805 10nF 10% 1 Vishay Cin C3225X7R1H335M Capacitor 1210 3.3µF, 50V 1 TDK Rsns ERJ8BQFR22V Resistor 1206 0.22Ω 1% 1 Panasonic Ron CRCW08056812F Resistor 0805 68.1kΩ 1% 1 Vishay Rz CRCW08050R00F Resistor 0805 0Ω 1 Vishay DIM1, DIM2, OFF 160-1512 Terminal 0.062” 3 Cambion GND1, GND2, GND3, VIN, Vo/LED+, CS/LED- 160-1026 Terminal 0.094” 6 Cambion J1 535676-5 Connector Custom 6 Pins 1 Tyco/AMP Table 2. Bill of Materials (LM3404HV) 4 ID Part Number Type Size Parameters Qty Vendor U1 LM3404HV LED Driver SO PowerPAD8 75V, 0.5A 1 Texas Instruments L1 SLF12555T- 680M1R3 Inductor 12.5 x 12.5 x 5.5mm 68µH, 1.3A, 83mΩ 1 TDK D1 CMSH2-100 Schottky Diode SMB 100V, 2A 1 Central Semi Cf VJ0805Y104KXXAT Capacitor 0805 100nF 10% 1 Vishay Cb VJ0805Y103KXXAT Capacitor 0805 10nF 10% 1 Vishay Cin C4532X7R2A225M Capacitor 1812 2.2µF, 100V 1 TDK Co1 C3216X7R2A105M Capacitor 1206 1.0µF, 100V 1 TDK Rsns ERJ8BQFR22V Resistor 1206 0.22Ω 1% 1 Panasonic Ron CRCW08051743F Resistor 0805 174kΩ 1% 1 Vishay Rz CRCW08050R00F Resistor 0805 0Ω 1 Vishay DIM1, DIM2, OFF 160-1512 Terminal 0.062” 3 Cambion GND1, GND2, GND3, VIN, Vo/LED+, CS/LED- 160-1026 Terminal 0.094” 6 Cambion J1 535676-5 Connector Custom 1 Tyco/AMP AN-1545 LM3404/LM3404HV Evaluation Board 6 Pins SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Evaluation Board Schematic www.ti.com 10 Evaluation Board Schematic VIN = 6V to 42V (LM3404) VIN = 6V to 75V (LM3404HV) CB BOOT VIN CIN L1 LED ANODE SW RON Q1 D1 RON Z1 LM3404/04HV CO1 RZ DIM2 RPD CS OFF RSNS DIM1 DIM GND VCC LED CATHODE CF Figure 4. Complete Evaluation Board Schematic SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback AN-1545 LM3404/LM3404HV Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 5 Typical Performance Characteristics 11 6 www.ti.com Typical Performance Characteristics Efficiency for Table 1 TA = 25°C, IF = 1.0A Efficiency for Table 2 TA = 25°C, IF = 1.0A IF vs VIN for Table 1 TA = 25°C IF vs VIN for Table 2 TA = 25°C AN-1545 LM3404/LM3404HV Evaluation Board SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Typical Performance Characteristics www.ti.com DIM Pin Enable for Table 1 DIM DIM Pin Disable for Table 1 DIM 5V/DIV 5V/DIV 500 mA/DIV IF IF 500 mA/DIV 1 és/DIV 2 és/DIV Switching Waveforms for Table 1 Output Ripple Current for Table 1 500 mA/DIV IF IF SW 50 mA/DIV 10V/DIV 1 és/DIV 1 és/DIV DIM Pin Enable for Table 2 DIM DIM Pin Disable for Table 2 5V/DIV DIM 5V/DIV 500 mA/DIV IF IF 500 mA/DIV 2 és/DIV SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback 4 és/DIV AN-1545 LM3404/LM3404HV Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 7 Typical Performance Characteristics www.ti.com Switching Waveforms for Table 2 Output Ripple Current for Table 2 500 mA/DIV IF IF SW 50 mA/DIV 20V/DIV 2 és/DIV 8 AN-1545 LM3404/LM3404HV Evaluation Board 2 és/DIV SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, Texas Instruments Incorporated Layout www.ti.com 12 Layout Figure 5. Top Layer and Top Overlay SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback AN-1545 LM3404/LM3404HV Evaluation Board Copyright © 2007–2013, Texas Instruments Incorporated 9 Layout www.ti.com Figure 6. Bottom Layer and Bottom Overlay 10 AN-1545 LM3404/LM3404HV Evaluation Board SNVA193E – January 2007 – Revised April 2013 Submit Documentation Feedback Copyright © 2007–2013, 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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