DEMO MANUAL DC2020A LT3955EUHE 60VIN 80VOUT LED Driver Description Demonstration circuit 2020A is a 60VIN, 80VOUT 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 60V and drives up to 67V of LEDs at 300mA (when PVIN is less than VLED). DC2020A 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 320Hz for DC2020A). 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 LT3955 data sheet in the applications section. Analog dimming is also simple to use with a single voltage source on the CTRL terminal. DC2020A features high efficiency at 350kHz switching frequency. At high LED string voltages up to 67V and 300mA of LED current, the single switch controller has 92% efficiency. The LT3955 has an internal 80V, 3.5A switch that simplifies the schematic and layout. Modifications can be made to DC2020A 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 LT3955 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 75V if the LED string is opened although it may reach 79V 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 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 5V. DC2020A PWM dimming is simplified when compared with other LED drivers. The LT3955 generates its own PWMOUT dimming waveform at a frequency determined The LT3955 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 DC2020A. The LT3955EUHE 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 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. dc2020afa 1 DEMO MANUAL DC2020A Performance Summary Specifications are at TA = 25°C PARAMETER CONDITIONS VALUE (TYPICAL) Input Voltage PVIN Range Operating 5V to VLED (up to 60V) Switching Frequency R1 = 28.7k 350kHz ILED RS1 = 0.82Ω 9V < PVIN < VLED (60V) 300mA Low PVIN ILED (CTRL foldback) RS1 = 0.82Ω PVIN = 7.0V RS1 = 0.82Ω PVIN = 8.0V 240mA 278mA VLED Range R7 = 1M R8 = 16.9k PVIN < VLED < 67V Open LED Voltage R7 = 1M R8 = 16.9k 75V Typical Efficiency 92.1% PVIN Under Voltage Lockout (falling turn-off) PVIN = 14V VLED = 67V ILED = 300mA PWM = INTVCC R3 = 499k and R4 = 165k PVIN Under Voltage Lockout (rising turn-on) R3 = 499k and R4 = 165k 6.1V INTVCC Operating 7.85V Peak Switch Current Limit 5.0V 3.3A PWMOUT Dimming Duty Cycle VDIM = 7.7V VDIM = 4.0V VDIM = 1.5V VDIM = 0.4V 96% 50% 10% 4.3% Internal PWM Dimming Frequency C16 = 0.047µF 0V < VDIM < 8V 300Hz Quick Start Procedure Demonstration circuit DC2020A is easy to set up to evaluate the performance of the LT3955EUHE. Follow the procedure below: 1. Connect a string of LEDs that will run with forward voltage less than or equal to 67V, but greater than the intended 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 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. 2 5. Turn the input power supply on and make sure the voltage is between 6.1V and 60V (or VLED) to start. 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 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. dc2020afa DEMO MANUAL DC2020A Quick Start Procedure IIN – + – VIN + + – PVIN OPTIONAL FOR SHUTDOWN + VOUT – + + – VDIM 0V TO 7.7V ILED – + 67V LED 300mA dc2020A F02 OPTIONAL FOR ANALOG DIMMING – OPTIONAL FOR EXTERNAL PWM DIMMING Figure 1. Test Procedure Setup Drawing for DC2020A dc2020afa 3 DEMO MANUAL DC2020A Quick Start Procedure 100% 98% 67VLED 300mA PWM = INTVCC EFFICIENCY 96% 94% 92% 90% 88% 86% 84% 82% 80% 0 5 10 15 20 25 30 35 40 45 50 PVIN (V) 55 60 dc2020a F02 Figure 2. DC2020A Efficiency with 67V LEDs at 300mA and 100% PWMOUT Duty Cycle VDIM = 8V DCPWM = 97.2% VDIM = 3.87V DCPWM = 50% ILED 0.3A/DIV VDIM = 1.47V DCPWM = 10% VIN = 24V VLED = 65V 0.5ms/DIV dc2020a F03 VDIM = 0V DCPWM = 2.8% Figure 3. DC2020A 300Hz PWM Dimming Waveforms at Different PWMOUT Duty Cycles 4 dc2020afa DEMO MANUAL DC2020A Quick Start Procedure 0.350 0.300 ILED (A) 0.250 0.200 0.150 UNDER0.100 VOLTAGE LOCKOUT 0.050 (FALLING) TURN-ON (RISING) 0.000 4 5 6 7 8 PVIN (V) 9 10 11 12 dc2020a F04 Figure 4. DC2020A CTRL LED Current Foldback at Low PVIN with UVLO (Falling and Rising) dc2020afa 5 DEMO MANUAL DC2020A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER CAP, 1206, 1µF, 20%, 100V, X7R TDK C3216X7R2A105MT Required Circuit Components 1 1 C1 2 2 C2, C3 CAP, 1210, 4.7µF, 10%, 100V, X7S TDK C3225X7S2A475K 3 4 C4, C5, C6, C7 CAP, 1210, 2.2µF, 20%, 100V, X7R TDK C3225X7R2A225M 4 0 C8, C14, C15 CAP, 1210, 2.2µF, 20%, 100V, X7R, OPTION TDK C3225X7R2A225M OPTION 5 1 C9 CAP, 0603, 4.7nF, 20%, 25V, X7R AVX 06033C472MAT2A 6 1 C10 CAP, 0603, 0.01µF, 10%, 25V, X7R AVX 06033C103KAT2A 7 1 C11 CAP, 0603, 1µF, 10%, 10V, X7R Taiyo Yuden LMK107BJ105KA 8 1 C16 CAP, 0603, 47nF, 20%, 16V, X7R Taiyo Yuden EMK107BJ473MA 9 1 D1 DIODE, SCHOTTKY DIODES INC. PDS3100-13 10 1 L1 IND, 22µH, 20% COOPER COILTRONICS DR125-220 11 1 M1 MOSFET N-CHANNEL 100V VISHAY SILICONIX Si2328DS 12 1 RS1 RES, 1206, 0.82Ω, 1%, 1/4W IRC LR1206LF-01-R820FT 13 1 R1 RES, 0402, 28.7kΩ, 1%, 1/16W VISHAY CRCW040228K7FKED 14 1 R2 RES, 0402, 5.1kΩ, 5%, 1/16W VISHAY CRCW04025K10JNED 15 1 R3 RES, 0603, 499kΩ, 1%, 1/16W VISHAY CRCW0603499KFKEA 16 1 R4 RES, 0402, 165kΩ, 1%, 1/16W VISHAY CRCW0402165KFKED 17 1 R5 RES, 0402, 1MΩ, 1%, 1/16W VISHAY CRCW04021M00FKED 18 1 R6 RES, 0603, 147kΩ, 1%, 1/16W VISHAY CRCW0603147KFKEA 19 1 R7 RES, 0603, 1MΩ, 1%, 1/16W VISHAY CRCW06031M00FKEA 20 1 R8 RES, 0402, 16.9kΩ, 1%, 1/16W VISHAY CRCW040216K9FKED 21 1 R9 RES, 0603, 100kΩ, 5%, 1/16W VISHAY CRCW0603100KJNED 22 1 R21 RES, 0402 124kΩ, 1% 1/16W VISHAY CRCW0402124KFKED 23 1 U1 IC, 60VIN/80VOUT LED DRIVER LINEAR TECH. LT3955EUHE Optional Electrical Components 1 0 C12, C13 CAP, 1210 OPTION 2 0 C17 CAP., 0603 OPTION 3 0 Q1 XSTR, OPTION OPTION OPTION 4 0 R10 RES, 0805, OPTION OPTION 5 1 R11 RES, 0805, 0Ω, JUMPER VISHAY CRCW08050000Z0EA 6 1 R12 RES, 1206, 0Ω, JUMPER VISHAY CRCW1206000Z 7 0 R13, R14, R16, R19, R20, R23 RES, 0603 OPTION OPTION 8 0 R15 RES, 1206 OPTION OPTION 9 0 R17, R18, R22 RES, 0402 OPTION OPTION 10 1 R24 RES, 0603, 0Ω JUMPER VISHAY CRCW06030000Z0EA Optional Hardware 1 9 E1, E2, E3, E4, E5, E7, E8, E12, E13 TURRET MILL MAX 2501-2-00-80-00-00-07-0 2 7 E6, E9, E10, E11, E14, E15, E16 TURRET MILL MAX 2308-2-00-80-00-00-07-0 6 dc2020afa E3 DIM PWM SYNC CTRL E6 E15 E9 R20 OPT 0603 E14 E10 EN/UVLO PGND VIN 5V - 60V* E2 R6 147k 1% R4 165k 1% 0603 R3 499k 0603 124k 1% C10 0.01µF R21 R5 1M 2. CAPACITORS ARE 0603 CASE SIZE. 1. RESISTORS ARE 0402 CASE SIZE. NOTES: UNLESS OTHERWISE SPECIFIED. C16 47nF 300Hz INTVCC R14 OPT 0603 SYNC R16 OPT 0603 OUT R15 OPT 1206 OUT R1 28.7k 350kHz 30 36 35 33 32 31 2 1 C9 4.7nF R2 5.1k SYNC C1 1µF 100V 1206 C3 4.7µF 100V 1210 OPT 0603 R13 R19 OPT 0603 OUT C2 4.7µF 100V 1210 R12 0 1206 VC RT DIM/SS PWM VREF CTRL PVIN OPT R18 D1 PDS3100-13 ISN ISP FB INTVCC VMODE PWMOUT U1 LT3955EUHE EN/UVLO SYNC L1 22µH 14 PVIN PGND E1 OPT 1210 C13 9 PGND 15 6 OPT 8 SW PGND 16 PVIN 5V - 60V* 10 NC 1210 38 SW PGND 17 VIN GNDK 12 SW GND 24 * SEE DEMO MANUAL FOR INPUT RANGE PGND 13 21 SW GND 37 20 SW GND 4 C12 3 34 23 27 28 25 R22 OPT C11 1µF 10V 0603 R9 100k C17 OPT Q1 OPT R17 OPT INTVCC -VMODE OPT 0603 R23 16.9k 1% R8 R7 1.00M 1% 0603 0 0603 R24 0 0805 R11 0.82 1% 1206 RS1 OUT SYNC C5 2.2µF 100V 1210 OPT 0805 R10 M1 Si2328DS C4 2.2µF 100V 1210 OUT C6 2.2µF 100V 1210 C14 OPT 1210 C7 2.2µF 100V 1210 C15 OPT 1210 INTVCC PGND OUT E16 E13 E12 E11 E8 INTVCC GND GND VMODE LED- E7 LED+ 67V LED MAX 300mA C8 OPT 1210 E4 E5 DEMO MANUAL DC2020A Schematic Diagram dc2020afa 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 DC2020A 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 dc2020afa Linear Technology Corporation LT 0413 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2013