DEMO MANUAL DC1666A LT3791 Four-Switch Buck-Boost LED Driver Controller Description Demonstration circuit DC1666A is a synchronous fourswitch buck-boost LED driver controller. It accepts an input voltage from 4.7V to 60V, and drives up to 25V of LEDs at 2A. DC1666A features both PWM and analog dimming of the LED string. It has an OPENLED flag that indicates when the LED string has been removed and it has a SHORTLED flag that indicates that the output has been shorted to GND. In both cases, the IC remains in control and well protected. DC1666A features very high efficiency at 300kHz switching frequency and continuous conduction mode (CCM). The synchronous four-switch topology both steps up and steps down voltage while regulating up to 50W of constant LED output current at efficiencies up to 98%. The circuit can be altered for applications requiring over 100W of LEDs. An optional SYNC terminal is provided for synchronizing to an external clock and CLKOUT terminal provides a source to sync another converter to the internal clock of the LT®3791. Three sense resistors provide constant output current control and monitoring, peak switch current control, and DC input current limit and monitoring. The ISMON and IVINMON outputs tell the user how much current is flowing through the output and input sense resistors. Small ceramic input and output capacitors are used to save space and cost. The open LED overvoltage protection uses the ICs constant voltage regulation loop to limit the output to approximately 28.3V if the LED string is opened. For low input voltage operation, the CTRL pin voltage is reduced as the input voltage drops below 6.5V, 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 4.7V. When input rises above 57.6V, overvoltage lockout turns the switches off to protect them and they turn back on when VIN drops below 56.2V. DC1666A PWM dimming is simple. The PWM dimming MOSFET 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 Applications Information section of the LT3791 data sheet. Analog dimming is also simple with a simple voltage source on the CTRL terminal. Modifications can be made to DC1666A in order to convert the board to higher or lower power or from an LED driver to a constant voltage regulator or battery charger. Please consult the factory or the LT3791 data sheet for details. The LT3791 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 DC1666A. The LT3791 is assembled in a 38-lead plastic 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, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. dc1666af 1 DEMO MANUAL DC1666A Performance Summary (TA = 25°C) PARAMETER CONDITION VALUE (TYPICAL) Input Voltage PVIN Range* Operating 4.7V to 60V* Switching Frequency R12 = 86.6k 300kHz ILED CTRL = Float, 7V < PVIN < 57.6V 2.0A VLED Range R7 = 1M, R9 = 44.2k 9.5V < VLED < 25.5V Open LED Voltage R7 = 1M, R9 = 44.2k 28.3V Typical Efficiency Boost Region PVIN = 20V, VLED = 25V, ILED = 2A 97.5% Typical Efficiency Buck-Boost Region PVIN = 24V, VLED = 25V, ILED = 2A 96.8% Typical Efficiency Buck Region PVIN = 30V, VLED=25V, ILED = 2A 97.3% Undervoltage Lockout (Falling Turn-Off) R13 = 332k and R6 = 115k 4.7V Undervoltage Lockout (Rising Turn-On) R13 = 332k and R6 = 115k 5.7V Overvoltage Lockout (Rising Turn-Off) R11 = 54.9k, R19 = 1M 57.6V Overvoltage Lockout (Falling Turn-On) R11 = 54.9k, R19 = 1M 56.2V Peak Switch Current Limit Boost Region RS = 0.004Ω 11A Valley Switch Current Limit Buck Region RS = 0.004Ω 10A * The guaranteed input voltage range of the LT3791 is 4.7V to 60V. Overvoltage lockout is set externally at 57.6V on this demo circuit to protect the 60V MOSFETs M1 and M2. Overvoltage lockout is adjustable. dc1666af 2 DEMO MANUAL DC1666A Quick Start Procedure Demonstration circuit DC1666A is easy to set up to evaluate the performance of the LT3791. Follow the procedure below: 5.Turn the input power supply on and make sure the voltage is between 4.7V and 60V. NOTE: PWM must be pulled high to run. If PWM is not used, connect PWM to a 5V source or to INTVCC on the PCB using 0Ω resistor R22. 6.Release the EN/UVLO to GND connection. 1. Connect a string of LEDs that will run with forward voltage less than 25.5V, but greater than 9.5V, 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. 7.Observe the LED string running at the programmed LED current. 8. 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. 9.Observe the reduction of brightness in the LED string when PWM or analog dimming. 4. Connect the PWM terminal. If PWM is not used, connect PWM to a 5V source or to INTVCC on the PCB using 0Ω resistor R22. PWM must be pulled high to run. dc1666af 3 DEMO MANUAL DC1666A quick start procedure Figure 1. Test Procedure Setup Drawing for DC1666A dc1666af 4 DEMO MANUAL DC1666A quick start procedure 100 98 EFFICIENCY (%) 96 BOOST BUCK 94 BUCK-BOOST 92 90 88 86 84 82 80 10 0 30 40 20 INPUT VOLTAGE (V) 60 50 3791 TA02b Figure 2. DC1666A Efficiency with 25V LEDs at 2A PWM 5V/DIV IL1 2A/DIV ILED 2A/DIV 50µs/DIV 3791 TA02c Figure 3. DC1666A 100Hz 50:1 PWM Dimming Waveforms at 12VIN and 25VLED at 2A 2.0 TURN-ON (FALLING) ILED (A) 1.5 UVLO (FALLING) 1.0 TURN-ON (RISING) OVLO (RISING) 0.5 0 3 4 5 6 9 7 8 INPUT VOLTAGE (V) 10 50 55 60 DC1666A F04 Figure 4. DC1666A CTRL LED Current Foldback at Low VIN with UVLO Falling and Rising and OVLO dc1666af 5 DEMO MANUAL DC1666A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Electrical Components 1 1 CSS CAP X7R 0.01µF 50V 10% 0603 AVX, 06035C103KAT2A 2 1 CC CAP X7R 0.022µF 50V 10% 0603 AVX, 06035C223KAT2A 5% 3 4 C2, C3, C12, C14 CAP X7R 2.2µF 100V 10% 1210 AVX, 12101C225KAT2A 4 1 C5 CAP X7R 1µF 100V 10% 1206 AVX, 12061C105KAT2A 5 3 C6, C8, C11 CAP X5R 0.1µF 16V 10% 0402 AVX, 0402YD104KAT2A 6 1 C7 CAP X5R 4.7µF 10V 10% 0603 AVX, 0603ZD475KAT2A 7 4 C9, C10, C13, C15 CAP X7R 4.7µF 50V 10% 1210 AVX, 12105C475KAT2A 8 2 D1-D2 DIODE Single Schottky Barrier Diode SOD-323 NXP, BAT46WJ 9 1 L1 INDUCTOR 10µH Cooper Bussmann, HC9-100-R 10 2 M1, M2 MOSFET N-Channel 60V LFPAK RENESAS, RJK0651DPB-00-J5 11 2 M3, M4 MOSFET N-Channel 40V LFPAK RENESAS, RJK0451DPB-00-J5 12 1 M5 MOSFET N-Channel 40V SOT-23 VISHAY, Si2318DS-T1-E3 13 1 RLED RES CHIP 0.050Ω 1% 2010 VISHAY, WSL2010R0500FEA 14 1 RS RES CHIP 0.004Ω 1W 1% 2010 VISHAY, WSL20104L000FEA 15 1 R7 RES CHIP 1M 1% 0402 VISHAY, CRCW04021M00FKED 16 1 R9 RES CHIP 44.2k 1% 0402 VISHAY, CRCW040244K2FKED 17 1 R12 RES CHIP 86.6k 1% 0402 VISHAY, CRCW040286K6FKED 18 1 U1 IC LT3791EFE 38-LEAD TSSOP VERSION AA TSSOP LINEAR, LT3791EFE#PBF Optional Electrical Components 1 1 C4 CAP X5R 0.47µF 6.3V 10% 0402 AVX, 04026D474KAT2A 2 0 C16, C17 CAP 1210 OPTIONAL 3 0 C18 CAP 0603 OPTIONAL 4 0 D3, D4 DIODE SMB OPTIONAL 5 2 RC, R16 RES CHIP 0Ω 0402 VISHAY, CRCW04020000Z0ED 6 1 RIN RES CHIP 0.003Ω 1W 1% 1206 IRC, ULR-G-1-1206-R003-1-LF-SLT 7 1 R2 RES CHIP 0Ω 1206 VISHAY, CRCW12060000Z0EA 8 1 R3 RES CHIP 1M 1% 0402 VISHAY, CRCW04021M00FKED 9 2 R4, R5 RES CHIP 200k 5% 0603 VISHAY, CRCW0603200KJNEA 10 1 R6 RES CHIP 115k 1% 0603 VISHAY, CRCW0603115KFKEA 11 1 R8 RES CHIP 237k 1% 0402 VISHAY, CRCW0402237KFKED 12 0 R10, R15, R18, R20, R21 RES CHIP 0402Ω 0402 OPTIONAL 13 1 R11 RES CHIP 54.9k 1% 0402 VISHAY, CRCW040254K9FKED 14 1 R13 RES CHIP 332k 1% 0402 VISHAY, CRCW0402332KFKED 15 1 R14 RES CHIP 0Ω 0603 VISHAY, CRCW06030000Z0EA 16 1 R17 RES CHIP 51Ω 5% 0402 VISHAY, CRCW040251R0JNED 17 1 R19 RES CHIP 1M 1% 0603 VISHAY, CRCW06031M00FKED 18 0 R22, R23 RES CHIP 0Ω 0603 OPTIONAL 22 E1-E22 TURRET 0.095 MILL-MAX, 2501-2-00-80-00-00-07-0 Hardware 1 dc1666af 6 D 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. A B C E21 E19 E20 E15 E13 E12 E11 E10 R4 200k 0603 E9 E17 E8 E4 R14 0 0603 5 ALL CAPACITORS ARE 0603. ALL RESISTORS ARE 0402. R19 1M VREF 9 R13 332k Css 10nF RIN R17 51 0.003 0402 C4 470nF 1210 IVINMON SS SYNC CLKOUT 4 U1 Cc 22nF Rc 0 OPENLED ISMON 12 PWM PWMOUT ISN ISP FB TG2 SW2 BG2 SNSN SNSP BG1 SW1 TG1 BST2 BST1 INTVCC R16 3 31 26 25 37 24 21 19 28 27 18 16 14 22 15 13 0 C7 4.7uF 10V 0603 C12 2.2uF 100V 1210 3 3 C16 (OPT) C18 OPT D4 OPT D2 BAT46WJ M3 RJK0451DPB SUMIDA HC9-100-R L1 10uH C6 0.1uF 0402 D1 BAT46WJ C14 2.2uF 100V 1210 C8 0.1uF 0402 OPT INTVCC RS 0.004 2010 M2 RJK0651DPB D3 OPT M1 RJK0651DPB 0603 R22 C3 2.2uF 100V 1210 R15 OPT C2 2.2uF 100V 1210 C5 1uF 100V 1206 R2 0 1206 LT3791EFE SHORTLED VREF NC CTRL OVLO EN/UVLO R12 86.6k 300kHz 2 34 33 7 8 4 5 6 23 1 38 R6 115k 0603 R20 OPT VREF 0402 C11 0.1uF R18 OPT R11 54.9k R10 OPT R8 237k OPENLED R5 200k 0603 INTVCC R3 1M PVIN NOTE: UNLESS OTHERWISE SPECIFIED GND GND SYNC CLKOUT ISMON IVINMON OPENLED SHORTLED CTRL OVLO EN/UVLO GND E1 4 RT 35 VC 36 PVIN 4.7V - 60V 10 IVINP 11 IVINN TEST1 29 SGND 30 PGND 39 PGND VIN 32 TEST2 PGND 20 R23 OPT 0603 M4 RJK0451DPB 2 M6 OPT C13 4.7uF 50V 1210 C15 4.7uF 50V 1210 INTVCC OPENLED C10 4.7uF 50V 1210 R21 OPT C9 4.7uF 50V 1210 R9 44.2k R7 1M 2 M5 0.05 2010 RLED INTVCC GND VIN 4.7V - 60V 1 Si2318DS C17 (OPT) E5 E3 E2 1 LED+ OUT E22 E7 E18 E16 GND PWM GND LED- E14 2A E6 A B C D Schematic Diagram 17 5 DEMO MANUAL DC1666A dc1666af 7 DEMO MANUAL DC1666A 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 dc1666af 8 Linear Technology Corporation LT 0312 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2012