DC1573A

DEMO MANUAL DC1573A LT3760 8-Channel 100mA High Voltage LED Driver Description DC1573A is an 8-Channel 100mA High Voltage LED Driver featuring the LT®3760. The LT3760 drives up to 100mA per string and has a maximum LED string voltage of 45V. DC1573A is set at 1MHz switching frequency for smallest inductor and capacitor size as well as maximum PWM dimming performance. Overvoltage protection is set at 55V in case the LEDs are removed from the circuit. If the LEDs are opened, the FAULT terminal output flag goes low and reports the fault condition. The VIN terminal is powered from 10V to 14V input separated from the 24V PVIN supply for best thermal performance. If one or more of the 8 LED channels is not used, its LED pin or terminal should be tied to LED+ to disable it. Multiple channels can be used in parallel for higher LED current by tying their LED1-8 pins together. PERFORMANCE SUMMARY PARAMETER The LT3760 data sheet gives a complete description of the part, operation and applications information. The data sheet must be read in conjunction with this demo manual for demonstration circuit 1573A. The LT3760 is assembled in a small 28-lead FE (4.4mm TSSOP) package with a thermally enhanced ground pad. Proper board layout is essential for maximum thermal performance. See the Layout Considerations section in the data sheet. Design files for this circuit board are available at http://www.linear.com/demo L, LT, LTC, LTM, µModule, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. (TA = 25°C) CONDITION VALUE (TYPICAL) PVIN Power Input Voltage Range Operating 20V to 28V VIN Pin Input Voltage Range Operating 8V to 14V Switching Frequency RT = 39.2k 1MHz LED String Current ILED(1-8) R14 = 5.76k 100mA OVP Open LED Voltage R8 = 11k, R7 = 20k 55V Efficiency PVIN = 24V, VIN = 10V, VLED = 45V, ILED1-8 = 100mA 92% Undervoltage Lockout R1 = 499k, R4 = 40.2k 20.1V Low Voltage Turn-On (UVLO + VHYST) R1 = 499k, R4 = 40.2k 21.4V Peak Switch Current Limit RS1 = 0.015Ω 3.3A dc1573af 1 DEMO MANUAL DC1573A quick start procedure Demonstration circuit 1573A is easy to set up to evaluate the performance of the LT3760. Follow the procedure below: Note: PWM must be pulled high to work. If PWM is not used, tie PWM high or connect to REF on the PCB using resistor R9. 1. Connect strings of LEDs with forward voltage less than 45V, but greater than the PVIN voltage, to the LED+ and LED1-8 terminals on the PCB as shown in Figure 1. Tie any unused LED1-8 pins directly to VOUT (LED+) before power-up to disable that channel. 2. Connect the SHDN terminal to GND. 3. With power off, connect the PVIN power supply to the PVIN and GND terminals within the range specified on the PCB. Make sure that the PVIN DC input voltage does not exceed the forward voltage of the LED string. 4. With power off, connect the VIN power supply to the VIN and GND terminals within the range specified on the PCB. 5. Connect the PWM terminal. If PWM is not used, tie PWM high or connect to REF on the PCB using resistor R9. PWM must be pulled high to work. 6. Turn the PVIN power supply on. 7. Turn the VIN power supply on after PVIN. 8. Release the SHDN-to-GND connection. 9. Observe the LED strings running at the programmed LED current. Note: For PWM dimming, connect a PWM (100Hz or higher) signal to the PWM terminal and observe the reduction of brightness in the LED string when PWM dimming. Figure 1. Proper Measurement Setup Drawing dc1573af 2 DEMO MANUAL DC1573A Terminal Options FAULT: The FAULT terminal is tied directly to the FAULT pin. If there is a fault condition, the FAULT terminal is pulled low. When there is no fault, the terminal is pulled up to VIN. This terminal can be monitored with a voltage meter, tied to the input of another device, or left floating. SYNC: This terminal is tied directly to the SYNC pin. As assembled, SYNC is disabled and tied directly to GND with a 0Ω resistor (R6). For SYNC to be used, R6 must be removed and a SYNC signal must be applied to this terminal. SHDN/UVLO: This terminal is tied directly to the SHDN/ UVLO pin. A resistor divider from PVIN to GND sets the voltage on this terminal/pin. These resistors can be easily adjusted for both the UVLO level and the amount of rising hysteresis. See the data sheet for details. The terminal can also be used to shut the IC down and turn off the LEDs. Tie the terminal directly to GND in order to place the IC in shutdown and turn off the LEDs. INTVCC: This terminal is tied directly to the INTVCC pin. This terminal is provided to be able to monitor the voltage on the INTVCC regulator or to provide an external INTVCC source to the IC. In some low voltage applications, INTVCC can be tied directly to PVIN or VIN. See the data sheet for details. For normal operation, leave this terminal floating. CTRL: This terminal is tied directly to the CTRL pin. As assembled, there is a 1M resistor pulling the CTRL pin up to REF. The CTRL pin voltage can be adjusted for analog dimming as shown in the data sheet. Either a voltage on the CTRL terminal can be driven to dim the LEDs or a resistor divider (R2 and R5) from PVIN to GND can be added to reduce the CTRL voltage as PVIN drops too low. Pulling the CTRL pin to GND turns the LEDs off. PWM: This terminal is tied directly to the PWM pin. As shown in the data sheet, an input PWM waveform turns the LEDs ON and OFF. Dimming frequency and dimming range are discussed in the data sheet. When PWM dimming is not being used, tie PWM to REF with a 0Ω resistor (R9) or place a 3.3V or 5V DC source on the PWM terminal. LED+ and LED1-8: The eight LED+ terminals are the output voltage of the boost regulator and they are all tied together on the PCB. The anodes of the LED strings should be tied to these terminals and the cathodes to LED1-8 terminals. If an LED1-8 terminal is not used, it should be tied directly to LED+. If all LED+ to LED1-8 connections are left floating or are opened during operation, DC1573A powers the output to 55V as programmed by OVPSET. It is okay to connect LEDs to the LED+ and LED1-8 terminals when it is powered to OVP. See data sheet for details. LED1-8 terminals can be tied together to get more than 100mA per LED string. Pairs of LED1-8 terminals can be tied together for 4× 200mA LED strings as an example. Individually, each LED1-8 pin can source a maximum of 100mA, but they can be tied together for more. dc1573af 3 DEMO MANUAL DC1573A parts list ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 1 CIN1 Capacitor, 1210 4.7µF 20% 25V X7R TDK C3225X7R1E475M 2 1 CIN2 Capacitor, 1210 4.7µF 10% 50V X7R AVX 12105C475KAT2A 3 5 C1, C2, C3, C4, C5 Capacitor, 1210 2.2µF 10% 100V X7R Murata GRM32ER72A225KA35L 4 1 C6 Capacitor, 0805 4.7µF 10% 10V X5R Taiyo Yuden LMK212BJ475KG-T 5 1 C7 Capacitor, 0402 2200pF 5% 50V X7R AVX 04025C222JAT2A 6 1 D1 Diode, Schottky Diodes Inc. PDS560 7 1 L1 Inductor, 10µH Sumida CDRH8D38NP-100NC 8 1 M1 MOSFET N-channel 60V Vishay Si7850DP-T1-E3 9 1 RS1 Resistor, 2010 0.015Ω 1% 1W IRC LRF2010LF-01-R015-F 10 1 RT Resistor, 0402 39.2kΩ 1% 1/16W Panasonic ERJ-2RKF3922X 11 1 R1 Resistor, 0603 499kΩ 1% 1/10W NIC NRC06F4993TRF 12 1 R4 Resistor, 0603 40.2kΩ 1% 1/10W NIC NRC06F4022TRF 13 2 R7, R10 Resistor, 0402 20kΩ 1% 1/16W NIC NRC04F2002TRF 14 1 R8 Resistor, 0402 11kΩ 1% 1/16W NIC NRC04F1102TRF 15 1 R11 Resistor, 0402 30.9kΩ 1% 1/16W NIC NRC04F3092TRF 16 1 R13 Resistor, 0402 10kΩ 5% 1/16W NIC NRC04J103TRF 17 1 R14 Resistor, 0402 5.76kΩ 1% 1/16W NIC NRC04F5761TRF 18 1 R18 Resistor, 0603 1MΩ 5% 1/10W Vishay CRCW06031M00JNEA 19 1 U1 IC, 8-Channel LED Driver Linear Technology LT3760EFE Optional Electrical Components 1 0 C10 Do Not Stuff Option 2 0 R2, R3, R5, R16 Resistor, 0603 Option Option 3 1 R6 Resistor 0603 0Ω Jumper NIC NR06Z0TRF 4 0 R9, R12 Do Not Stuff Option 5 1 R15 Resistor, 0603 100kΩ 5% 1/10W NIC NRC06J104TRF 6 1 R17 Resistor, 0402 0Ω Jumper Vishay CRCW04020000Z0ED 1 14 E1-E6, E13, E40-E46 Turret MILL MAX 2501-2-00-80-00-00-07-0 2 16 E7, E9-E11, E14-E16, E18-E20, E22, E23, E27, E31, E35, E39 Turret MILL MAX 2308-2-00-80-00-00-07-0 Hardware dc1573af 4 INTVCC GND SYNC PWM CTRL GND SHDN/UVLO FAULT GND PVIN 20V TO 28V GND R6 OPT R9 OPT R7 20k 1% R8 11k 1% E46 E43 REF R11 30.9k 1% R10 20k 1% R12 OPT REF OVPSET SYNC PWM NC CTRL Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. R13 10k 100mA C7 2200pF R13 10k 14 VIN U1 LT3760EFE SHDN/UVLO FAULT 2 TSET 13 INTVCC C6 4.7µF 10V 3 28 17 E13 5 27 R18 1M R5 OPT E6 E5 E40 1 15 R4 40.2k 1% R2 OPT CIN2 4.7µF 25V CIN1 4.7µF 25V E4 R1 499k 1% R16 OPT 16 R3 OPT R15 100k E3 E41 E1 E2 E45 VC 26 ISET 4 PGND 10 E9 E11 E14 E16 E18 E20 E22 8 9 20 21 22 23 DC1573A F02 24 E7 7 RS1 0.015Ω M1 Si7850DP D1 PDS560 6 18 R17 0Ω 1 2 3 11 C10 OPT 4 8 7 6 5 12 RT 39.2k 1MHz GND LED8 LED7 LED6 LED5 LED4 LED3 LED2 LED1 VOUT SENSE GATE L1 10µH CDRH8D38NP PGND 19 PGND 29 RT 25 VIN 10V TO 14V LED+ LED+ LED+ LED+ LED+ LED+ LED3 LED4 LED5 LED6 LED7 LED8 E44 E42 E39 E35 E31 E27 E23 E19 E15 E10 C5 2.2µF 100V 1210 LED+ C4 2.2µF 100V 1210 LED2 C3 2.2µF 100V 1210 LED+ C2 2.2µF 100V 1210 LED1 C1 2.2µF 100V 1210 GND GND DEMO MANUAL DC1573A Schematic Diagram dc1573af 5 DEMO MANUAL DC1573A DEMONSTRATION BOARD IMPORTANT NOTICE Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES. The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged. This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer. Mailing Address: Linear Technology 1630 McCarthy Blvd. Milpitas, CA 95035 Copyright © 2004, Linear Technology Corporation dc1573af 6 Linear Technology Corporation LT 0311 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com  LINEAR TECHNOLOGY CORPORATION 2011