DEMO MANUAL DC2079A LT3954 40VIN 40VOUT LED Driver Description Demonstration circuit 2079A is a 40VIN, 40VOUT LED driver. It generates its own PWMOUT waveform from its internal PWM generator for accurate PWM dimming with up to 33:1 brightness ratio. It accepts an input voltage from 5V to 30V and drives up to 32V of LEDs at 650mA (when PVIN is less than VLED). DC2079A features both PWM and analog dimming of the LED string. It has an OPENLED flag that indicates when the LED string has been removed. by the capacitance on the PWM pin (C16 gives 300Hz for DC2079A). The PWMOUT duty cycle is determined by the voltage on the DIM terminal. Between 0V and 8V VDIM gives between 3% and 97% PWM duty cycle. Information regarding PWM dimming ratios and performance can be found in the LT3954 data sheet in the applications section. Analog dimming is also simple to use with a single voltage source on the CTRL terminal. DC2079A features high efficiency at 350kHz switching frequency. At high LED string voltages up to 32V and 650mA of LED current, the single switch controller has 94.6% efficiency (14V input). The LT3954 has an internal 40V, 5.4A switch that simplifies the schematic and layout. Modifications can be made to DC2079A in order to convert the board to power different LED strings 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 LT3954 data sheet for details. It can be modified to provide LED+ to GND short-circuit protection as well. 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 35V if the LED string is opened although it may reach 38V peak during transient from running LEDs to open string. For low input voltage operation, the CTRL pin voltage is reduced as the input voltage drops below 8.5V, 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 5.3V. DC2079A PWM dimming is simplified when compared with other LED drivers. The LT3954 generates its own PWMOUT dimming waveform at a frequency determined The LT3954 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 DC2079A. The LT3954EUHE is assembled in a 36-lead plastic QFN package with two thermal pads underneath the IC. 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, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. dc2079af 1 DEMO MANUAL DC2079A Performance Summary Specifications are at TA = 25°C PARAMETER CONDITION VALUE (TYPICAL) Input Voltage PVIN Range Operating 5V to VLED (Up to 40V) Switching Frequency R1 = 28.7k 350kHz ILED RS1 = 0.39Ω 8.4V < PVIN < VLED (40V) 645mA Low PVIN ILED (CTRL Foldback) RS1 = 0.39Ω, PVIN = 6.0V RS1 = 0.39Ω , PVIN = 7.0V RS1 = 0.39Ω, PVIN = 8.0V 486mA 577mA 640mA VLED Range R7 = 1M, R8 = 37.4k PVIN < VLED < 32V Open LED Voltage R7 = 1M, R8 = 37.4k 34.8V Typical Efficiency PVIN =14V, VLED = 32V, ILED = 645mA PWM = INTVCC 94.6% PVIN Undervoltage Lockout (Falling Turn-Off) R3 = 499k and R4 = 147k 5.3V PVIN Undervoltage Lockout (Rising Turn-On) R3 = 499k and R4 = 147k 6.5V INTVCC Operating 7.85V Peak Switch Current Limit 5.4A PWMOUT Dimming Duty Cycle VDIM = 8.0V VDIM = 4.0V VDIM = 1.5V VDIM = 0V 97.5% 50% 10% 3.1% Internal PWM Dimming Frequency C16 = 0.047µF, 0V < VDIM < 8V 300Hz dc2079af 2 DEMO MANUAL DC2079A Quick Start Procedure Demonstration circuit DC2079A is easy to set up to evaluate the performance of the LT3954. Follow the procedure below: 5. Turn the input power supply on and make sure the voltage is between 6.5V and 40V (or VLED) to start. 1. Connect a string of LEDs that will run with forward voltage less than or equal to 32V, but greater than the intended PVIN, to the LED+ and LED– terminals on the PCB as shown in Figure 1. 7. Observe the LED string running at the pro-grammed LED current and brightness related to the programmed PWMOUT duty cycle. 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 40V (or VLED). 4. Connect the DIM terminal to a voltage between 0V and 8V 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. 6. Release the EN/UVLO-to-GND connection. 8. To change the brightness with PWM dimming, simply vary the VDIM voltage between 0V and 8V 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. dc2079af 3 DEMO MANUAL DC2079A Quick Start Procedure Figure 1. Test Procedure Setup Drawing for DC2079A dc2079af 4 DEMO MANUAL DC2079A Quick Start Procedure 100 32VLED 650mA PWM = INTVCC 98 EFFICIENCY (%) 96 94 92 90 88 86 84 82 80 5 15 10 20 30 25 PVIN (V) DC2079A F02 Figure 2. DC2079A Efficiency with 32V LEDs at 650mA and 100% PWMOUT Duty Cycle VDIM = 8V DCPWM = 97.5% VDIM = 3.9V DCPWM = 47% ILED 500mA/DIV VDIM = 1.5V DCPWM = 10% VDIM = 0V DCPWM = 3.1% DC2079A F03 VIN = 12V VLED = 32V Figure 3. DC2079A 300Hz PWM Dimming Waveforms at Different PWMOUT Duty Cycles 0.7 0.6 ILED (A) 0.5 0.4 UNDER VOLTAGE LOCKOUT 0.2 (FALLING) 0.3 TURN-ON (RISING) 0.1 0 4 5 6 7 8 PVIN (V) 9 10 11 12 DC2079A F04 Figure 4. DC2079A CTRL LED Current Foldback at Low PVIN with UVLO (Falling and Rising) dc2079af 5 DEMO MANUAL DC2079A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Cap., X5R 1µF 50V 20% 1206 TDK C3216X5R1H105M Required Circuit Components 1 1 C1 2 1 C2 Cap., X5R 10µF 50V 20% 1210 Taiyo Yuden UMK325BJ106MM-T 3 2 C4, C5 Cap., X5R 4.7µF 50V 20% 1210 Taiyo Yuden UMK325BJ475MM-T 4 1 C9 Cap., X7R 4.7nF 25V 20% 0603 AVX 06033C472MAT2A 5 1 C10 Cap., X7R 0.01µF 25V 10% 0603 AVX 06033C103KAT2A 6 1 C11 Cap., X7R 1µF 10V 10% 0603 Taiyo Yuden LMK107BJ105KA 7 1 C16 Cap., X7R 47nF 16V 20% 0603 Taiyo Yuden EMK107BJ473MA 8 1 D1 Schottky Diode 5A PowerDi5 Diodes Inc. PDS560-13 9 1 L1 Inductor, 22µH Cooper Coiltronics DR125-220 10 1 M1 Mosfet N-Chan., 40V SOT23 Siliconix Si2318CDS-T1-GE3 11 1 RS1 Res., Chip 0.39, 0.25W 1% 1206 Panasonic ERJ-8RQFR39V 12 1 R1 Res., Chip 28.7k 0.06W 1% 0402 Vishay CRCW040228K7FKED 13 1 R2 Res., Chip 5.1k 0.06W 5% 0402 Vishay CRCW04025K10JNED 14 1 R7 Res., Chip 1.00M 0.06W 1% 0603 Vishay CRCW06031M00FKEA 15 1 R8 Res., Chip 37.4k 0.06W 1% 0402 Vishay CRCW040237K4FKED 16 1 R21 Res., Chip 124k 0.06W 1% 0603 Vishay CRCW0603124KFKEA 17 1 U1 I.C.,40Vin/ 40Vout LED Driver Linear Tech. Corp. LT3954EUHE Optional Circuit Components 1 1 C3 Cap., X5R 10µF 50V 20% 1210 Taiyo Yuden UMK325BJ106MM-T 2 0 C6-C8, C12-C15 Cap., 1210 Optional 3 0 C17 Cap., 0603 Optional 4 0 Q1 Diode, SOT23 Optional 5 1 R3 Res., Chip 499k 0.06W 1% 0603 Vishay CRCW0603499KFKEA 6 1 R4 Res., Chip 147k 0.06W 1% 0603 Vishay CRCW0603147KFKEA 7 1 R5 Res., Chip 1M 0.06W 1% 0402 Vishay CRCW04021M00FKED 8 1 R6 Res., Chip 165k 0.06W 1% 0402 Vishay CRCW0402165KFKED 9 1 R9 Res., Chip 100k 0.06W 5% 0603 Vishay CRCW0603100KJNEA 10 0 R10 Res., 0805 Optional 11 1 R11 Res., Chip 0Ω 0.33W 6A 0805 Vishay CRCW08050000ZOEA 12 1 R12 Res., Chip 0Ω 0.5W 10A 1206 Vishay CRCW12060000ZOEA 13 0 R13, R14, R16, R19, R20, R23 Res., 0603 Optional 14 0 R15 Res., 1206 Optional 15 0 R17, R18, R22 Res., 0402 Optional 16 1 R24 Res., Chip 0Ω 0.25W 5A 0603 Vishay CRCW06030000Z0EA 1 9 E1-E5, E7, E8, E12, E13 Turret, Testpoint Mill Max 2501-2-00-80-00-00-07-0 2 7 E6, E9-E11, E14-E16 Turret, Testpoint Mill Max 2308-2-00-80-00-00-07-0 Hardware dc2079af 6 E3 DIM PWM SYNC CTRL E6 C16 47nF 300Hz INTVCC R14 (Opt) 0603 SYNC R16 (Opt) 0603 OUT R15 (Opt) 1206 R6 165k 1% 124k 1% 0603 R21 R5 1M R4 147k 1% 0603 R3 499k 0603 C10 0.01µF 2. CAPACITORS ARE 0603 CASE SIZE. 1. RESISTORS ARE 0402 CASE SIZE. NOTES: UNLESS OTHERWISE SPECIFIED. E15 E9 R20 (Opt) 0603 E14 E10 EN/UVLO PGND VIN 5V - 30V* E2 OUT R1 28.7k 1% 350kHz (Opt) 0603 R13 R19 (Opt) 0603 OUT C2 10µF 50V 1210 30 36 35 33 32 C9 4.7nF R2 5.1k 2 1 31 C1 1µF 50V 1206 SYNC C3 10µF 50V 1210 R12 0 Ohm 1206 DIM/SS PWM VREF CTRL VC D1 PVIN (Opt) R18 PDS560-13 ISN ISP FB INTVCC VMODE PWMOUT U1 LT3954EUHE EN/UVLO SYNC RT L1 22µH DR125-220 14 PVIN PGND 15 E1 C13 (Opt) 1210 9 PGND PVIN 5V - 30V* 10 NC C12 8 SW PGND 16 6 12 38 SW PGND 17 VIN GNDK 13 SW GND 24 * SEE DEMO MANUAL FOR INPUT RANGE PGND 21 SW GND 37 20 SW GND 4 (Opt) 1210 3 34 23 27 28 25 R22 (Opt) RS1 C11 1µF 10V 0 Ohm 0603 100k 0603 0 Ohm 0805 R11 0.39 1% 1206 R24 INTVCC -VMODE (Opt) 0603 R23 37.4k 1% R8 R7 1.00M 1% 0603 R9 C17 (Opt) Q1 (Opt) R17 (Opt) SYNC OUT C5 4.7µF 50V 1210 (Opt) 0805 R10 M1 Si2318DS C4 4.7µF 50V 1210 OUT C6 (Opt) 1210 C14 (Opt) 1210 C7 (Opt) 1210 C15 (Opt) 1210 INTVCC E16 E13 E12 E11 E8 E7 C8 (Opt) 1210 E4 E5 INTVCC GND GND VMODE LED- LED+ 32V LED MAX 650mA PGND OUT DEMO MANUAL DC2079A Schematic Diagram dc2079af 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 DC2079A 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 dc2079af 8 Linear Technology Corporation LT 0413 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2013