DEMO MANUAL DC1772A LT3761EMSE High Voltage LED Controller with Internal PWM Dimming Description DC1772A is a high voltage LED controller with internal PWM dimming. It generates its own PWMOUT waveform for accurate PWM dimming with up to 25:1 brightness ratio. It accepts an input voltage from 8V to 60V (8V UVLO and 9.1V rising turn-on), and drives up to 60V of LEDs at 1A (when PVIN is less than VLED). DC1772A features both PWM and analog dimming of the LED string. It has an OPENLED flag that indicates when the LED string has been removed. DC1772A features high efficiency at 350kHz switching frequency. At high LED string voltages up to 60V and 1A of LED current, the single switch controller has 94% efficiency. The open LED overvoltage protection uses the IC’s constant voltage regulation loop to regulate the output to approximately 69.8V if the LED string is opened although it may reach 74V peak during transient from running LEDs to open. The maximum LED string voltage can be raised from 60V to 65V (or higher) with a simple change of feedback resistors. For low input voltage operation, the CTRL pin voltage is reduced as the input voltage drops below 10V, reducing LED brightness and restraining the peak switch currents in order to limit inductor and switch size. UVLO turns the LEDs off when PVIN drops below 8V. DC1772A PWM dimming is simplified when compared with other LED drivers. The LT®3761 generates its own PWMOUT dimming waveform at a frequency determined by the capacitance on the PWM pin (C8 gives 300Hz for DC1772A). The PWMOUT duty cycle is determined by the voltage on the DIM terminal. Between 0V and 7.7V VDIM gives between 4% and 96% PWM duty cycle. Information regarding PWM dimming ratios and performance can be found in the LT3761 data sheet in the Applications Information section. Analog dimming is also simple to use with a single voltage source on the CTRL terminal. Modifications can be made to DC1772A 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 the LT3761 data sheet for details. It can be modified to provide LED+ to GND short-circuit protection as well. The LT3761 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 DC1772A. The LT3761EMSE is assembled in a 16-lead plastic MSOP MSE 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. dc1772af 1 DEMO MANUAL DC1772A Performance Summary Specifications are at TA = 25°C PARAMETER CONDITION Input Voltage PVIN Range Operating Switching Frequency R6 = 29.4k ILED RS2 = 0.25Ω 10V < PVIN < VLED (60V) Low PVIN ILED (CTRL Foldback) RS2 = 0.25Ω PVIN = 8.5V RS2 = 0.25Ω PVIN = 9V VLED Range R3 = 1M R4 = 18.2k PVIN < VLED < 60V Open LED Voltage R3 = 1M R4 = 18.2k 69.8V Typical Efficiency PVIN = 14V VLED = 60V ILED = 1A PWM = INTVCC PVIN Under Voltage Lockout (Falling Turn-Off) R1 = 499k and R2 = 90.9k 8V PVIN Under Voltage Lockout (Rising Turn-On) R1 = 499k and R2 = 90.9k 9.1V INTVCC Operating 7.85V Peak Switch Current Limit RS1 = 0.008Ω 12.5A PWMOUT Dimming Duty Cycle VDIM = 7.7V VDIM = 4V VDIM = 1.5V VDIM = 0.4V 96% 50% 10% 4.3% Internal PWM Dimming Frequency C8 = 0.047µF 0V < VDIM < 7.7V VALUE (TYPICAL) 8V to VLED (Up to 60V) 350kHz 1A 930mA 975mA 94% 300Hz Quick Start Procedure Demonstration circuit 1772A is easy to set up to evaluate the performance of the LT3761EMSE. Follow the procedure below: 1.Connect a string of LEDs that will run with forward voltage less than 60V, but greater than PVIN, to the LED+ and LED– terminals on the PCB as shown in Figure 1. 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 60V (or VLED). 4.Connect the DIM terminal to a voltage between 0V and 7.7V to set the internal PWMOUT dimming duty cycle. If this terminal is left floating the converter will run with approximately 12% PWMOUT dimming duty cycle. Pull the PWM terminal high to INTVCC to set the converter at 100% duty cycle. 2 5.Turn the input power supply on and make sure the voltage is between 8V and 60V (or VLED). 6.Release the EN/UVLO-to-GND connection. 7.Observe the LED string running at the programmed LED current and brightness related to the programmed PWMOUT duty cycle. 8.To change the brightness with PWM dimming, simply vary the VDIM voltage between 0V and 7.7V with the PWM terminal floating. 9.To change the brightness with analog dimming, simply attach a voltage source on the CTRL terminal and reduce the voltage below 1.2V. 10.Observe the reduction of brightness in the LED string when PWM or analog dimming. dc1772af DEMO MANUAL DC1772A Quick Start Procedure Figure 1. Test Procedure Setup Drawing for DC1772A dc1772af 3 DEMO MANUAL DC1772A Quick Start Procedure 100% 60VLED 1.0A PWM = INTVCC 98% 96% EFFICIENCY (%) 94% 92% 90% 88% 86% 84% 82% 80% 0V 5V 10V 15V 20V 25V 30V 35V 40V 45V 50V 55V 60V PVIN INPUT VOLTAGE (V) Figure 2. DC1772A Efficiency with 60V LEDs at 1A and 100% PWMOUT Duty Cycle VDIM = 7.7V DCPWM = 96% VDIM = 4V DCPWM = 50% ILED 1A/DIV VDIM = 1.5V DCPWM = 10% VDIM = 0.4V DCPWM = 4.3% 0.5ms/DIV Figure 3. DC1772A 300Hz PWM Dimming Waveforms at Different PWMOUT Duty Cycles 4 dc1772af DEMO MANUAL DC1772A Quick Start Procedure 1.2 1.0 ILED (A) 0.8 0.6 under voltage lockout (falling) 0.4 0.2 turn-on (rising) 0.0 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12 PVIN (V) Figure 4. DC1772A CTRL LED Current Foldback at Low PVIN with UVLO Falling and Rising dc1772af 5 DEMO MANUAL DC1772A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 2 C1, C10 Cap., X7S 4.7µF 100V 10% 1210 TDK C3225X7S2A475K 2 4 C2, C3, C11, C12 Cap., X7R 2.2µF 100V 10% 1210 TDK C3225X7R2A225K 3 1 C4 Cap., X7R 1µF 100V 20% 1206 TDK C3216X7R2A105M 4 1 C5 Cap., X5R 1µF 10V 10% 0603 AVX, 0603ZD105KAT2A 5 1 C6 Cap., X7R 4700pF 25V 20% 0603 AVX, 06033C472MATAT2A 6 1 C7 Cap., X5R 0.01µF 16V 20% 0603 AVX, 0603YD103MAT2A 7 1 C8 Cap., X7R 0.047µF 50V 10% 0603 AVX, 06035C473KAT2A 8 1 D1 Schottky Diode 5A PowerDi5 Diodes Inc. PDS5100H 9 1 L1 Inductor, 10µH HC9-SERIES/COOPER Cooper Bussmann, HC9-100-R 10 1 M1 MOSFET N-Chan., 100V Infineon, BSC123N08NS3G 11 1 M2 MOSFET N-Chan., 100V Siliconix Si2328DS-T1-GE3 12 1 RS1 Res., Chip., 0.008Ω 1/2W 1% 2010 Vishay WSL20108L000FEA 13 1 RS2 Res., Chip., 0.25Ω 1/2W 1% 1206 Vishay WSL1206R2500FEA 14 1 R1 Res., Chip, 499k 0.06W 1% 0402 Vishay CRCW0402499KFKED 15 1 R2 Res., Chip, 90.9k, 0.06W 1% 0402 Vishay CRCW040290K9FKED 16 1 R3 Res., Chip, 1M, 0.1W 1% 0603 Vishay CRCW06031M00FKED 17 1 R4 Res., Chip, 18.2k, 0.06W 1% 0402 Vishay CRCW040218K2FKED 18 1 R5 Res., Chip 10k, 0.06W 5% 0402 Vishay CRCW040210K0JKED 19 1 R6 Res., Chip, 29.4k, 0.06W 1% 0402 Vishay CRCW040229K4FKED 20 1 R7 Res., Chip 1M, 0.06W 5% 0402 Vishay CRCW04021M00JKED 21 1 R8 Res., Chip, 140k, 0.06W 1% 0402 Vishay CRCW0402140KFKED 22 1 R9 Res., Chip 100k, 0.1W 5% 0603 Vishay CRCW0603100KJKEA 23 1 R10 Res., Chip, 124k, 0.1W 1% 0603 Vishay CRCW0603124KFKED 24 1 U1 I.C., LED Driver MSOP(16)-MSE Linear Tech. Corp. LT3761EMSE Optional Electrical Components 1 0 C9, C13(OPT) Cap., 1210 2 0 C14, C15 (OPT) Cap., 0603 3 0 D2 (OPT) Rectifier, ESIC SMA 4 0 D3 (OPT) Diode, 1N4148W, SOD-123 5 0 M3 (OPT) MOSFET N-Chan., SOT23 (OPT) 6 0 M4 (OPT) MOSFET P SO8-PWR (OPT) 7 0 Q1, Q2, Q3 (OPT) PNP SOT23 (OPT) 8 1 R11 Res., Chip, 0Ω, 1206 Vishay CRCW12060000Z0EA Vishay CRCW06030000Z0ED 9 1 R12 Res., Chip 0Ω, 0603 10 0 R13, R17, R19-22 (OPT) Res., 0402 11 0 R14, R24 (OPT) Res., 0805 12 0 R15 (OPT) Res., 1206 13 0 R16, R18, R23, R25-R27 (OPT) Res., 0603 E1-E14 Turret, Testpoint Optional Hardware 1 6 14 Mill Max 2501-2-00-80-00-00-07-0 dc1772af GND DIM OPENLED INTVCC CTRL EN/UVLO PGND VIN 8V - 60V PVIN 8V - 60V 124k 0603 R10 R2 90.9k 1% C5 1uF R9 100k 10V 0603 R8 140k 1% R7 1M 1% R1 499k 1% C10 4.7uF 100V 1210 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. RESISTORS ARE IN 0402. CAPACITORS ARE IN 0603. 14 10 5 ISN ISP FB 17 GND 8 1 3 4 2 350kHz R6 29.4k 1% 11 RT PWM PWMOUT R5 10k C6 4700pF DIM/SS VC OPENLED C7 U1 0.008 RS1 15 2010 LT3761EMSE INTVCC CTRL VREF EN/UVLO PDS5100H D1 C14 OPT R4 18.2k 1% R18 OPT 0603 LED+ C13 OPT 1210 OPT OPTIONAL for SHORT CIRCUIT R27 OPT 0603 FB R26 OPT 0603 D3 C12 2.2uF 100V 1210 INTVCC Q3 OPT SOT23 0603 R23 OPENLED C11 2.2uF 100V 1210 OPT OUT C3 2.2uF 100V 1210 M3 OPT OPT. INTVCC C8 0.047uF FB R3 1.0M 1% 0603 R13 C2 2.2uF 100V 1210 OPTIONAL for BUCK MODE M1 BSC123N08NS3 GATE SENSE 16 COOPER R11 0 1206 VIN 0.01uF 9 13 6 R22 OPT 7 12 C4 1uF 100V 1206 C1 4.7uF 100V 1210 NOTE: UNLESS OTHERWISE SPECIFIED OPT OUT R17 OPT 0603 OUT R16 OPT 1206 OUT R15 PVIN L1 10uH HC9-100-R OPT 1210 C9 RS2 PVIN 0603 R25 OPT OPT M4 OPT D2 OPT FB R19 R21 OPT OPT Q1 OPT SOT23 OUT 0 0603 R12 M2 Si2328DS OPTIONAL for SHORT CIRCUIT R20 OPT C15 R14 OPT 0805 SOT23 OPT Q2 OUT OPTIONAL LEVEL SHIFT for BUCK MODE or BUCK-BOOST MODE 0.25 1% 1/2W 1206 GND PWM R24 OPT 0805 LED - LED + 60VLED 1A OUT DEMO MANUAL DC1772A Schematic Diagram dc1772af 7 DEMO MANUAL DC1772A 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 8 dc1772af Linear Technology Corporation LT 1012 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2012