DEMO MANUAL DC1827A LT3795 110V LED Controller with Spread Spectrum Frequency Modulation Description Demonstration Circuit 1827A features a 110V LED controller with spread spectrum frequency modulation - the LT®3795. Unlike most boosts, the circuit disconnects the output to protect against shorts or other fault conditions when the input voltage exceeds the output. The input voltage range for normal operation is from 8V to 60V. OVLO becomes active for inputs above 63V and the maximum input voltage is 110V. The LED current is 400mA and the switching frequency is 250kHz. The efficiency is 92% when the input is 12V and the LED voltage is at 87V which is the maximum LED voltage. Spread spectrum switching is available to simplify conducted emissions compliance. There is a 47nF capacitor from the RAMP pin to ground to set the rate at which frequency modulation occurs, but resistor R20 shorting the RAMP pin capacitor must be removed to activate spread spectrum. OVLO and EN/UVLO are both set using resistor dividers. EN/UVLO is set so the circuit will UVLO when the input voltage falls below 6V and will turn on when the input voltage rises above 7.5V. Current sense resistors program LED current and input regulation current and also determine the monitoring voltages that indicate output and input current. The LED current is set by RS2. ISMON provides a 2.5V/1A voltage that is used to monitor the LED current. Input current regulation occurs at 4A and is set by RS3. IVINCOMP provides a 300mV/1A voltage that is used to monitor the input current. Capacitor C11 on the IVINCOMP pin provides compensation for the input current regulation loop. CTRL1 and CTRL2 are analog dimming inputs that allow external voltages to reduce the LED current from the programmed maximum. CTRL1 and CTRL2 are pulled up to the VREF pin by 100k resistors. SHORTLED and OPENLED are open-collector status flag outputs that are pulled up to the INTVCC pin voltage. The circuit requires application of an external voltage to the PWM terminal for operation. The external voltage can be a DC level or an appropriate pwm dimming signal. A common frequency for PWM dimming is 100Hz. The high-side PMOS FET that is used for pwm dimming also disconnects the output to protect against shorts. The soft-start pin (SS) is configured so the circuit will hiccup when a fault occurs and will not latch off. The demo circuit also supports the adjustment capability of the LT3795 for switching frequency and feedback loop compensation. The FB pin is programmed using a resistor divider to limit the output voltage in case there is no LED string on the output. When an open LED transient occurs either at start up or because the LED string opens, the peak output voltage may overshoot to 100V but FB will regulate the settled output voltage to 95V. The demo circuit uses ceramic input and output capacitors. An aluminum electrolytic capacitor can be easily added to the input if it is necessary for stability during conducted emissions testing. The 120V switching MOSFET allows 110V on the input. FB programming inhibits switching at high output voltages so the 100V rating of the rectifier is not exceeded. The demo circuit is designed to be easily reconfigured to buck mode, buck-boost mode and SEPIC topologies. There are example schematics in the data sheet. Consult the factory for assistance. Maximum input and output voltages of 110V, spread spectrum switching, fault protection and full monitoring make the LT3795 attractive for high voltage and high power LED circuits, battery chargers and voltage regulators that require an accurate current limit. DC1827A uses the LT3795EFE which is packaged in a thermally enhanced 28-lead TSSOP. The LT3795 data sheet must be read in conjunction with this demo manual to properly use or modify DC1827A. Design files for this circuit board are available at http://www.linear.com/demo/DC1827A 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. dc1827af 1 DEMO MANUAL DC1827A Performance Summary Specifications are at TA = 25°C PARAMETER CONDITIONS MIN Minimum Input, VPVIN VLED = 87V, ILED ≤ 400mA Maximum Input – Switching,VPVIN VLED = 87V, ILED ≤ 400mA 60 V Maximum Input – Not Switching, VPVIN VOVLO ≥ 1.25V 110 V 87 V Maximum LED Voltage, VLED TYP MAX 8 UNITS V LED Current, ILED RS2 = 0.62Ω 400 mA Input EN Voltage, VPVIN(EN) VPVIN Rising R1 = 499k, R2 = 115k, R3 = 12.4k 7.5 V Input UVLO Voltage, VPVIN(UVLO) VPVIN Falling R1 = 499k, R2 = 115k, R3 = 12.4k 6 V Input OVLO Turn-Off Voltage, VPVIN(OVLO_TURN-OFF) VPVIN Rising R1 = 499k, R2 = 115k, R3 = 12.4k 63.1 V Input OVLO Turn-On Voltage, VPVIN(OVLO_TURN-ON) VPVIN Falling R1 = 499k, R2 = 115k, R3 = 12.4k 62.1 V Efficiency VPVIN =12V, VLED = 87V, ILED = 400mA VPVIN =24V, VLED = 87V, ILED = 400mA VPVIN =48V, VLED = 87V, ILED = 400mA 92 91 92 % % % Switching Frequency R5 = 31.6k 250 kHz Input Current Limit RS3 = 0.015Ω 4 A Quick Start Procedure It is easy to set up DC1827A to evaluate the performance of the LT3795. Follow the procedure below: NOTE: PWM must be pulled high to work. If PWM is not used, connect the PWM terminal to a 2V to 5V DC source or connect the PWM pin to VREF on the PCB using R18. 1.Connect a string of LEDs with a forward voltage of 87V or less, but greater than the PVIN voltage, to the LED+ and GND terminals on the PCB as shown in Figure 1. 2.Connect the EN/UVLO terminal to GND. 3.With the power off, connect the input power supply to the PVIN and GND terminals within the voltage range specified on the PCB. Make sure that the input power supply voltage does not exceed the forward voltage of the LED string. OVLO becomes active to inhibit switching for an input voltage greater than 63V. 2 4.Connect an input to the PWM terminal. If PWM is not used, connect PWM to a 2V to 5V DC source or to VREF on the PCB using resistor R18. PWM must be pulled high to work. For PWM dimming, connect a 100Hz or higher PWM signal to the PWM terminal. 5.Turn the PVIN power supply on. 6.Release the EN/UVLO to GND connection. 7.Observe the LED string running at the programmed LED current; or, observe the reduction of brightness in the LED string with PWM dimming. dc1827af DEMO MANUAL DC1827A Quick Start Procedure Figure 1. Proper Measurement Equipment Setup for DC1827A dc1827af 3 DEMO MANUAL DC1827A Quick Start Procedure 100 100 95 80 47nF AT RAMP PIN 70 EFFICIENCY (%) AMPLITUDE (dBµV) 87VLED 400mA RAMP PIN GROUNDED 90 60 50 40 30 20 0 150 200 80 70 350 250 300 FREQUENCY (kHz) 85 75 EMI AVERAGE SA DETECTOR 10 90 0 10 20 30 40 PVIN (V) 0.45 70 Figure 3. DC1827A Efficiency with 87VLED at 400mA 12VIN, 87VLED 400mA 87VLED 0.40 60 DC1827A F03 DC1827A F02 Figure 2. Conducted Emissions without Spread Spectrum (RAMP Pin Grounded) and the Improvement that Occurs with Spread Spectrum Switching (47nF at RAMP Pin) 50 LED CURRENT (A) 0.35 0.30 200 TO 1 ILED 100mA/DIV 0.25 100 TO 1 67 TO 1 0.20 0.15 750 TO 1 500 TO 1 0.10 0.05 0 –0.05 0 5 10 60 65 PVIN (V) 110 115 20µs/DIV DC1827A F05 DC1827A F04 Figure 4. The LED String is 87V. This Output Current vs Input Voltage Graph Shows the Wide Input Voltage Range and the Input Voltages at Which UVLO, Turn-On and OVLO Occur. Input Current Limit Occurs When VIN Is 10V or Less. 4 Figure 5. LED Current During PWM Dimming at 100Hz dc1827af DEMO MANUAL DC1827A Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 1 C1 Cap., X7R 1µF 100V 20% 1206 AVX 12061C105MAT2A 2 7 C2, C3, C4, C7, C8, C9 Cap., X7R 2.2µF 100V 10% 1210 Murata GRM32ER72A225KA35L 3 1 C5 Cap., X5R 4.7µF 10V 10% 0603 AVX 0603ZD475KAT2A 4 1 C6 Cap., X7R 0.1µF 25V 10% 0603 AVX 06033C104KAT2A 5 1 C12 Cap., X7R 0.01µF 10V 10% 0603 AVX 0603ZC103KAT1A 6 1 D1 Schottky Diode 5A POWERDI5 Diodes Inc. PDS5100-13 7 1 L1 Inductor, 22µH HC9-SERIES Cooper Bussmann HC9-220-R 8 1 M1 Mosfet N-Channel, 120V/44A Super SO8 Infineon BSC190N12NS3G 9 1 M2 Mosfet P-Channel, 150V PowerPak 1212-8 Vishay Siliconix Si7115DN-T1-E3 10 1 RS1 Res., LRC 0.015 0.5W 1% 2010 IRC LRC-LR2010LF-01-R015-F 11 1 RS2 Res., LRC 0.620 0.5W 1% 2010 SEI CSRN2010FKR620 12 1 R4 Res., Chip 1.00M 0.06W 1% 0603 NIC NRC06F1004TRF 13 1 R5 Res., Chip 31.6k 0.06W 1% 0402 Vishay CRCW040231K6FKED 14 1 R6 Res., Chip 13.3k 0.06W 1% 0402 Vishay CRCW040213K3FKED 15 1 R7 Res., Chip 10k 0.06W 5% 0402 Vishay CRCW040210K0JNED 16 1 U1 I.C., LED Driver TSSOP28-FE/EB Linear Tech. Corp. LT3795EFE C10 Optional Demo Circuit Components 1 1 C13 Cap., X5R 0.1µF 25V 10% 0603 AVX 06033C104KAT2A 2 1 C11 Cap., X7R 0.01µF 10V 10% 0603 AVX 0603ZC103KAT1A 3 1 C14 Cap., X7R 0.047µF 16V 10% 0603 AVX 0603YC473KAT1A 4 0 C15, C16, C17, C18, Cap., 1210 C19 5 0 C20 Cap., 0402 6 0 C21 Cap., 12.5mm Dia. 7 1 D2 Ultra Fast Rect., 150V/1A SMA 8 0 M3 Mosfet N-Channel SOT23 9 0 Q1,Q2 Trans., PNP SOT23 Zetex FMMT593 10 1 RS3 Res., LRC 0.015 0.5W 1% 2010 IRC LRC-LR2010LF-01-R015-F 11 1 R1 Res., Chip 499k 0.06W 1% 0603 Vishay CRCW0603499KFKEA 12 1 R2 Res., Chip 115k 0.06W 1% 0402 Vishay CRCW0402115KFKED 13 1 R3 Res., Chip 12.4k 0.06W 1% 0402 Vishay CRCW040212K4FKED 14 1 R8 Res./Jumper, Chip 0Ω 1/4W 1A 1206 Vishay CRCW12060000ZOEA 15 0 R9 Res., 1206 16 0 R10, R15, R19, R22 Res., 0402 17 1 R11 Res/Jumper, Chip 0Ω 1/16W 1A 0402 18 0 R12, R13, R14, R18, R21, R23, R24, R25, R26, R27, R30, R31, R32 Res., 0603 19 4 R16, R17, R28, R29 Res., Chip 100k 0.06W 5% 0402 Vishay CRCW0402100KJNED 20 1 R20 Res./Jumper, Chip 0Ω 1/16W 1A 0603 Vishay CRCW06030000Z0EA Fairchild Semi. ES1C Vishay CRCW04020000Z0ED dc1827af 5 DEMO MANUAL DC1827A Parts List ITEM QTY REFERENCE PART DESCRIPTION 18 E1, E2, E3, E4, E5, E6, E7, E8, Turret, Testpoint E9, E10, E11, E12, E13, E14, E15, E16, E17, E18 MANUFACTURER/PART NUMBER Hardware 1 6 Mill Max 2501-2-00-80-00-00-07-0 dc1827af VIN 8V - 60V 110V MAX. 63V OVLO 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. GND GND ISMON PWM CTRL2 CTRL1 GND E3 PVIN E8 E7 E6 + R15 (OPT) R13 (OPT) 0603 R9 (OPT) 1206 R20 0 Ohm 0603 R17 100k R14 (OPT) 0603 VOUT C2 2.2uF 100V 1210 C21 (OPT) 12.5mm DIA. SMD VOUT C13 0.1uF C1 1uF 100V 1206 R8 0 Ohm 1206 E5 E10 E9 E4 E2 PVIN 8V - 60V 110V MAX. 63V OVLO EN/UVLO E1 R18 (OPT) 0603 C4 2.2uF 100V 1210 INTVCC C14 0.047uF C5 4.7uF 10V R19 (OPT) R16 100k VREF C3 2.2uF 100V 1210 R10 (OPT) R1 499k 1% 0603 PVIN C6 0.1uF (OPT) R22 20 5 13 14 6 9 10 23 24 R3 12.4k 1% OVLO 25 11 SS IVINN 26 TG ISN ISP FB SENSE GATE 19 VC OPENLED SHORTLED 17 21 22 29 8 16 15 28 3 2 1 7 18 C12 0.01uF R7 10k M1 BSC190N12NS3G GND GND GND GND GND 4 L1 22uH HC9-220-R Cooper Bussmann IVINN IVINCOMP U1 LT3795EFE R5 31.6k 1% 250kHz 12 RT INTVCC ISMON RAMP PWM CTRL2 CTRL1 VREF VIN 27 0.015 1% 2010 RS3 R32 (OPT) 0603 PVIN IVINP R2 115k 1% EN/UVLO 0 Ohm R11 R12 (OPT) 0603 VOUT RS1 0.015 1% 2010 C7 2.2uF 100V 1210 (OPT) 1210 (OPT) 1210 C18 (OPT) 1210 C17 (OPT) 1210 C16 C15 100k R28 C8 2.2uF 100V 1210 100k R29 VREF (OPT) R6 0603 M3 13.3k (OPT) 1% SOT23 R24 (OPT) 0603 R23 /OPENLED C11 0.01uF R4 1.00M 1% 0603 PDS5100-13 D1 R21 (OPT) 0603 C10 2.2uF 100V 1210 INTVCC /OPENLED C9 2.2uF 100V 1210 IVINN R27 (OPT) 0603 Q1 (OPT) SOT23 C19 (OPT) 1210 R25 (OPT) 0603 PVIN R30 (OPT) 0603 R26 (OPT) 0603 WARNING! C20 (OPT) 0402 R31 (OPT) 0603 Q2 (OPT) SOT23 0.620 1% 2010 RS2 HIGH VOLTAGE E13 GND E14 GND E12 LED+ 400mA 87V D2 ES1C E11 VOUT OPENLED SHORTLED IVINCOMP E18 GND E17 E16 E15 M2 Si7115DN-T1-E3 VOUT DEMO MANUAL DC1827A Schematic Diagram dc1827af 7 DEMO MANUAL DC1827A 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 dc1827af Linear Technology Corporation LT 0713 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com LINEAR TECHNOLOGY CORPORATION 2013