DEMO MANUAL DC1706A LT3796 100V LED Controller with Current Monitor DESCRIPTION DC1706A is a 100V LED controller with an input current monitor. It is a single switch boost LED driver with LED+ to GND short circuit protection. It accepts an input voltage from 8V to 100V (7.5V UVLO and 8.7V turn-on), and drives up to 85V of LEDs at 400mA (when PVIN is less than VLED). DC1706A features both PWM and analog dimming of the LED string. It has a VMODE flag that indicates when the LED string has been removed and it has a FAULT flag that indicates that the output has been shorted to GND. In both cases, the IC remains in control and well protected. DC1706A features high efficiency at 300kHz switching frequency. At high LED string voltages up to 85V and 400mA of LED current, the single switch controller has 93% efficiency. There are input current (CSOUT) and output current (ISMON) monitor pins that deliver a voltage proportional to the current for quick diagnostics. Small ceramic input and output capacitors are used to save space and cost. The open LED overvoltage protection uses the IC’s constant voltage regulation loop to regulate the output to approximately 92.5V if the LED string is opened although it may reach 96.5V peak during transient from running LEDs to open. For low input voltage operation, the CTRL pin voltage is reduced as the input voltage drops below 9V, reducing LED brightness and restraining the peak switch currents in order to limit inductor and switch size. UVLO turns the LEDs off when VIN drops below 7.5V. DC1706A PWM dimming is simple. The topside PWM dimming MOSFET (M2) turns the LED string on and off with an input to the PWM dimming terminal. For the highest PWM dimming ratio, it is recommended to use 100Hz as a PWM dimming frequency. Information regarding PWM dimming ratios and performance can be found in the LT3796 data sheet in the applications section. Analog dimming is also simple to use with a single voltage source on the CTRL terminal. Modifications can be made to DC1706A in order to convert the board to higher or lower power or from an LED driver to a constant voltage regulator or battery charger. It can easily be changed from a boost topology to a SEPIC, buck mode, or buck-boost mode LED driver. Please consult the factory or refer to the LT3796 data sheet for details. The LT3796 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 DC1706A. The LT3796 is assembled in a 28lead plastic TSSOP FE package with a thermally enhanced ground pad. Proper board layout is essential for maximum thermal performance. See the data sheet section Layout Considerations. Design files for this circuit board are available at http://www.linear.com/demo L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. dc1706af 1 DEMO MANUAL DC1706A PERFORMANCE SUMMARY (TA = 25°C) PARAMETER CONDITIONS UNITS Input Voltage PVIN Range Operating 7.5V to VLED Switching Frequency R18 = 26.1k 300kHz ILED RS2 = 0.62Ω, 9V < PVIN < VLED 400mA Low PVIN ILED (CTRL Foldback) RS2 = 0.62Ω, PVIN = 8V 350mA VLED Range R5 = 1M, R9 = 13.7k PVIN < VLED < 85V Open LED Voltage R5 = 1M, R9 = 13.7k 92.5V Typical Efficiency PVIN = 14V, VLED = 85V, ILED = 400mA 93% Under Voltage Lockout (Falling Turn-Off) R1 = 499k and R8 = 100k 7.5V Under Voltage Lockout (Rising Turn-On) R1 = 499k and R8 = 100k 8.7V VINTVCC Operating 7.7V Peak Switch Current Limit RS3 = 0.015Ω 6.6A Suggested Maximum PWM Dimming Ratio fPWM = 100Hz, PVIN=12V, VLED = 85V, ILED = 400mA 100:1 QUICK START PROCEDURE DC1706A is easy to set up to evaluate the performance of the LT3796. Follow the procedure below: 5. Turn the input power supply on and make sure the voltage is between 8V and VLED. NOTE: PWM must be pulled high to run. If PWM is not used, connect PWM to a 3.3V or 5V source or to VREF on the PCB using 0Ω resistor R24. 6. Release the EN/UVLO-to-GND connection. 1. Connect a string of LEDs that will run with forward voltage less than 85V, but greater than PVIN, to the LED+ and GND terminals on the PCB as shown in Figure 1. 8. Observe the CSOUT and ISMON input and output current monitor voltages. 2. Connect the EN/UVLO terminal to GND. 3. With power off, connect the input power supply to the PVIN and GND terminals. Make sure that the PVIN DC input voltage will not exceed 100V (or VLED). 4. Connect the PWM terminal. If PWM is not used, connect PWM to a 3.3V or 5V source or to VREF on the PCB using 0Ω resistor R24. PWM must be pulled high to run. 7. Observe the LED string running at the programmed LED current. 9. For PWM dimming, connect a PWM (100Hz or higher is recommended) signal to the PWM terminal. For analog dimming, connect a DC voltage between 0V and 2V to the CTRL terminal. 10. Observe the reduction of brightness in the LED string when PWM or analog dimming. dc1706af 2 DEMO MANUAL DC1706A QUICK START PROCEDURE Figure 1. Test Procedure Setup Drawing for DC1706A dc1706af 3 DEMO MANUAL DC1706A QUICK START PROCEDURE 100 85VLED 400mA 98 96 94 EFFICIENCY (%) 92 90 88 86 84 82 80 0 10 20 30 50 40 PVIN INPUT VOLTAGE (V) 60 70 80 90 DC1706a F02 Figure 2. DC1706A Efficiency with 85V LEDs at 400mA ILED 100mA/DIV 100:1 1000:1 85VLED PVIN = 12V 500:1 250:1 125:1 fPWM = 100Hz DC1706a F03 Figure 3. DC1706A 100Hz 100:1 to 1000:1 PWM Dimming Waveforms at 12V PVIN and 85V VLED dc1706af 4 DEMO MANUAL DC1706A QUICK START PROCEDURE 0.45 0.40 0.35 ILED (A) 0.30 TURN-ON (RISING) 0.25 UNDER VOLTAGE LOCKOUT (FALLING) 0.20 0.15 0.10 0.05 0 7 7.5 8 8.5 9 9.5 PVIN (V) 10 10.5 11 11.5 12 DC1706a F04 Figure 4. DC1706A CTRL LED Current Foldback at Low PVIN with UVLO Falling and Rising dc1706af 5 DEMO MANUAL DC1706A PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 2 C1, C2 CAP, X7S 4.7μF 100V 10% 1210 TDK C3225X7S2A475K 2 5 C3, C4, C5, C6, C12 CAP, X7R 2.2μF 100V 10% 1210 MURATA GRM32ER72A225KA35L 3 1 C8 CAP, X5R 4.7μF 10V 10% 0603 AVX 0603ZD475KAT2A 4 1 C9 CAP, X7R 0.01μF 25V 10% 0603 AVX 06033C103KAT2A 5 1 C11 CAP, X7R 0.1μF 25V 10% 0603 AVX 06033C104KAT2A 6 1 D1 SCHOTTKY DIODE 100V 5A POWERDI5 DIODES INC PDS5100H 7 1 L1 INDUCTOR, 22μH HC9-SERIES COOPER BUSSMANN HC9-220-R 8 1 M1 MOSFET N-CHAN, 100V/15A LFPAK RENESAS RJK1051DPB-00-J5 #PbF 9 1 M2 MOSFET P-CHAN, 100V POWERPAK 1212-8 SILICONIX Si7113DN-T1-E3 #PbF 10 1 RS2 RES, LRC 0.620 0.5W 1% 2010 IRC LR2010LF-01-R620-F 11 1 RS3 RES, 0.015 0.5W 1% 2010 VISHAY WSL2010R0150FEA 12 1 R5 RES, CHIP 1M 0.06W 1% 0402 VISHAY CRCW04021M00FKED 13 1 R9 RES, CHIP 13.7k 0.06W 1% 0402 VISHAY CRCW040213K7FKED 14 1 R16 RES, CHIP 4.7k 0.06W 5% 0402 VISHAY CRCW04024K70JNED 15 1 R18 RES, CHIP 26.1k 0.06W 1% 0402 VISHAY CRCW040226K1FKED 16 1 U1 100V LED CONTROLLER IC TSSOP28-FE/EB LINEAR TECHNOLOGY LT3796 Optional Electrical Components 1 0 C13, C14, C15 CAP, 1210 OPTIONAL 2 1 C16 CAP, X7R 0.01μF 25V 10% 0603 AVX 06033C103KAT2A 3 1 C17 CAP, X7R 0.1μF 25V 10% 0603 AVX 06033C104KAT2A 4 1 D2 SCHOTTKY RECT, 150V/1A SMA FAIRCHILD SEMI ES1C 5 0 D3 DIODE, SOD-123 OPTIONAL 6 0 M3 MOSFET SOT23 OPTIONAL 7 1 Q1 TRANS, PNP SOT23 ZETEX/DIODES INC FMMT589 8 1 RS1 RES, 0.025 0.5W 1% 2010 VISHAY WSL2010R0250FEA 9 1 R1 RES, CHIP 499k 0.06W 1% 0402 VISHAY CRCW0402499KFKED 10 3 R2, R4, R17 RES/JUMPER, CHIP 0Ω 1/16W 1A 0402 VISHAY CRCW04020000Z0ED 11 1 R3 RES, CHIP 2k 0.06W 1% 0402 VISHAY CRCW04022K00FKED 12 1 R6 RES/JUMPER, CHIP 0Ω 1/4W 1A 1206 VISHAY CRCW12060000ZOEA 13 1 R7 RES, CHIP 1M 0.06W 1% 0402 VISHAY CRCW04021M00FKED 14 1 R8 RES, CHIP 100k 0.06W 1% 0402 VISHAY CRCW0402100KFKED 15 1 R10 RES, CHIP 137k 0.06W 1% 0402 VISHAY CRCW0402137KFKED 16 0 R11, R12, R15, R19 TO R22, R25, R27, R28, R31, R33 RES 0402 OPTIONAL 17 2 R13, R14 RES, CHIP 100k 0.06W 5% 0402 18 0 R24, R30, R32 RES, 0603 OPTIONAL 19 1 R26 RES/JUMPER, Chip 0Ω 1/16W 1A 0603 VISHAY CRCW06030000Z0EA 20 1 R29 RES, CHIP 82.5k 0.06W 1% 0402 VISHAY CRCW040282K5FKED 21 0 R34 RES, 1206 OPTIONAL VISHAY CRCW0402100KJNED Optional Hardware 1 18 E1 TO E18 TURRET, TESTPOINT MILL MAX 2501-2-00-80-00-00-07-0 dc1706af 6 DEMO MANUAL DC1706A SCHEMATIC DIAGRAM dc1706af 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. 7 DEMO MANUAL DC1706A 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 dc1706af 8 Linear Technology Corporation LT 0512 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2012