DESCRIPTION The is a V synchronous dual LED driver with I C featuring the LT 94. It drives two separate LEDs (or channels of LEDs) at A when V IN is between V and V. runs at MHz switching frequency. Its two channels can drive separate LED strings which can have different currents, voltages, or dimming ratios. It can be controlled with I C communications or it can be run in non-i C mode with proper ADDR pin settings. It is protected against both open and short LED conditions and reports the faults. In I C mode, faults can be enabled or disabled. Up to 9 different s can be placed on the same I C bus with unique addresses. A graphical user interface (GUI) is available through QuikEval when connected to a DC0C Linduino One demo circuit. The LT94 has an input voltage range from 4V to V. It has two independent.a, 40V bucks with internal, synchronous 40V switches for high efficiency and small size. It has adjustable switching frequency between 00kHz and MHz. It can be synchronized to an external source or programmed with a clock output (CLKOUT) from the serial interface. The PWMTG high side PWM MOSFET drivers assist with short-circuit protection and versatility. Although the demo circuit is optimized for just one LED per channel, it can be altered to be buck regulators with as high as V of LEDs if V IN is high enough and circuit components are changed appropriately. DEMO MANUAL LT94 V Synchronous Dual LED Driver with I C In non-i C mode, each channel can separately be PWMand analog-dimmed by placing a PWM signal or CTRL voltage on the provided turrets. In I C mode, each channel can be dimmed to up to 89: and analog dimmed to a high ratio using serial communications. 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 4.V if the LED string is opened. There is a protection diode from each LED+ to to prevent negative ringing during a short-circuit condition. Undervoltage lockout can be adjusted on the circuit with a few simple resistor choices. The output voltage (overvoltage protection) can be adjusted by changing the feedback resistors for higher string voltages. Other components may need to be changed to accommodate higher voltages also. The LT94 data sheet gives a complete description of the device, operation and applications information. The data sheet must be read in conjunction with this demo manual for. The LT94EUHE is assembled in a -lead plastic mm mm QFN package with a thermally enhanced ground pad. Proper board layout is essential for maximum thermal performance. See the data sheet Layout Considerations section. Design files for this circuit board are available at http://www.linear.com/demo/ L, LT, LTC, LTM, Linear Technology, the Linear logo and Linduino are registered trademarks and QuikEval is a trademark of Analog Devices, Inc. All other trademarks are the property of their respective owners.
PERFORMANCE SUMMARY Specifications are at T A = C PARAMETER CONDITION MIN TYP MAX Input Voltage PV IN Range Operating V V Switching Frequency R8 = 7.4k.0MHz I LED, I LED R = R = 0.Ω.0A Open LED Voltage V OUT (V COUT) R0 = R4 = M R = R = 8k 4.V Efficiency (00% PWM DC).0V PV IN, MHz, I LED = I LED =.0A, LED 8% V LED Range R0 = R4 = M R = R=8k.V.V I C PWM Dimming Frequency R8 = 7.4k 44Hz PV IN Undervoltage Lockout (Falling) R = k R = 0k.0V PV IN Turn-On Voltage (Rising) R = k R = 0k.0V QUICK START PROCEDURE How to Operate in Non-I C Mode The is easy to set up to evaluate the performance of the LT94 in non-i C mode. Follow the procedure below:. With power off, connect a single LED between LED+ and LED terminals and the same for LED+ and LED. Connect the EN/UVLO terminal to to keep the circuit shut down. With power off, connect the input power supply to the V IN and terminals. Make sure that the input voltage will not exceed V.. For non-i C mode operation, set both JP and JP (ADDR and ADDR) to 0. The 00 address pins setting is for non-i C mode, but all other settings are for I C serial communications mode.. Turn the input power supply on and make sure the voltage is between 8V and V to start operation. 4. Release the EN/UVLO-to- connection.. Observe the LED string running at the programmed LED current.. To change the brightness with analog dimming in non- I C mode, simply attach a voltage source the CTRL and/or CTRL terminals and set the voltage between 0V and.v. See data sheet for details. 7. To change brightness with external PWM dimming in non-i C mode, simply attach a rectangular waveform with varying duty cycle to the PWM and/or PWM terminals. How to Operate with Graphical User Interface (GUI) I C Serial Communications Mode. With power off, connect a single LED between LED+ and LED terminals and the same for LED+ and LED. Connect the EN/UVLO terminal to to keep the circuit shut down. With power off, connect the input power supply to the V IN and terminals. Make sure that the input voltage will not exceed V.. For I C serial communications operation, set JP (ADDR) to 0 and JP (ADDR) to. The 0 address setting works seamlessly with the GUI in QuikEval. In general, serial communications can be used with the LT94 as long as ADDR and ADDR settings are anything other than 00. There are three states to each ADDRX pin, 0,, or float. There are 9 unique I C address settings.. Connect a ribbon cable between the J serial communications connection and a Linduino One (DC0C) demo circuit. 4. Connect a USB cable between a PC and the DC0C.. Turn on V power to the PV IN and pins of the.
QUICK START PROCEDURE. Launch QuikEval (find installation instructions on the www.linear.com website) and the LT94 GUI launches. 7. Use the GUI in QuikEval to test the performance of the LT94 demo circuit. DEMO MANUAL NOTE: A LT94 GUI user guide is posted on the landing page for the LT94 and. It contains the GUI pages, commands, and other details. Please contact Linear support for help with the GUI and User Guide. Figure. Test Procedure Setup Drawing for Figure. Efficiency vs Input Voltage with MHz and Single A LED on Each Channel Figure. PWM Dimming Using I C Settings for 89: and 048: Dimming Ratios
PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components C, C7 CAP., μf, XR,, 0%, MURATA, GRM88RH0KAALD C0, C CAP., 4.7μF, X7R,0V,0%, MURATA, GRMBR7A47KA7L 4 C, C4 CAP., 0μF, XR,, 0%, 0 MURATA, GRMCRH0KAL C CAP.,.μF, XR, V, 0%, MURATA, GRM88REME84D 7 C9, C CAP., 0.μF, XR, V, 0%, 040 MURATA, GRMRE4KE0D 9 L, L INDUCTOR,.μH WURTH ELEKTRONIK, 74480 M, M MOSFET P-CH, 0V,.9A, SOT- VISHAY, SiEDS-T-GE R RES., k, /W, %, 040 VISHAY, CRCW040KFKED 4 R RES., 0k, /W, %, 040 VISHAY, CRCW0400KFKED R RES., 00k, /W, %, 040 VISHAY, CRCW04000KFKED R RES., 499k, /W, %, 040 VISHAY, CRCW040499KFKED R7 RES., K, /W, %, 040 VISHAY, CRCW040KFKED 7 R8 RES., 7.4k, /W, %, 040 VISHAY, CRCW0407K4FKED 8 R, R RES., 8k, /W, %, 040 VISHAY, CRCW0408KFKED 0 R0, R4 RES., M, /W, %, 040 VISHAY, CRCW040M00FKED R, R RES., 0.Ω, /W, %, SUSUMU, KRL0E-M-R00-F-T 4 U I.C. LED DRIVER QFN- LINEAR, LT94EUHE#PBF Optional Electrical Components 0 C, C8 () CAP., ION C CAP., ALUM., µf,,. 7.7 SUNCON, 0CEFS 8 0 C, C, C8, C9 () CAP., 040 ION 9 0 C4 () CAP., 0 ION 0 C CAP., 0.μF, X7R, V,0%, MURATA, GRM88R7C04KA0D D, D DIODE SCHOTTKY, 0V, A, SODF NXP., PMEG00EJ, 4 0 FB, FB, FB () FERRITE BEAD, CHIP, 0 0 L () INDUCTOR,.μH WURTH ELEKTRONIK, 74480 4 R4, R, R, R7 RES., 00k, /W, %, 040 VISHAY, CRCW04000KFKED 9 0 R9, R () RES,, 0 R, R7, R, R, R4, R RES, 040 ION R8, R9, R0 RES., 4.99k, /0W, %, VISHAY, CRCW4K99FKEA U I.C., EEPROM -KBIT 400kHz 8-TSSOP MICROCHIP, 4LC0-I/ST Hardware E-E TESTPOINT, TURRET, 0.094" PBF MILL-MAX, 0--00-80-00-00-07-0 7 E7-E TESTPOINT, TURRET, 0.0" PBF MILL-MAX, 08--00-80-00-00-07-0 JP, JP HEADER, PIN, 0.079 DOUBLE ROW WURTH ELEKTRONIK, 000 4 JP HEADOR, PIN, 0.079", SINGLE ROW WURTH ELEKTRONIK, 000 XJP, XJP, XJP SHUNT, 0.079" CENTER WURTH ELEKTRONIK, 08004 J HEADER, 7 DUAL ROW MOLEX, 878-40 4
SCHEMATIC DIAGRAM C 0uF 0 R 499K FLOAT 0 0 FLOAT NOTE: UNLESS OTHERWISE SPECIFIED. ALL RESISTORS ARE 040. ALL CAPACITORS ARE 040. 00 IS NON-I C MODE. SCL SDA EEVCC TP FB R 00K R SUSUMU 0.OHM% J 4 7 0 9 4 V+ V CS SCK/SCL MOSI/SDA MISO EEVCC EESDA EESCL EE GPIO 8 C C4 0 U LT94EUHE + C uf C7 C uf 4 EN/UVLO BST 9 SW SW 0 SUNCON-CE-FS R R EN 0K R4 E7 4 VIN VIN FB 4 C9 0.uF CTRL E8 R4 00K 4 CTRL CTRL VIN VIN TSET ISP 8 ISN 7 PWMTG BST 8 SW SW 7 FB R R9 R7 K R8 7.4K MHz RT ISP 9 ISN 0 PWMTG R 00K 8 R7 00K SYNC/CLKOUT 7 PWM PWM SCL 0 SCL SDA 9 R 8K C R SUSUMU 0.OHM% E LED+ R4 M R 8K C8 R7 M SiEDS D PMEG00EJ E E LED+ TP4 R8 4.99K TP 8 7 U VCC C 0.uF A0 WP A SCL A SDA VSS 4 R JP 4LC0 NO WRITE WRITE CUSTOMER NOTICE LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. TITLE: SCHEMATIC TECHNOLOGY 0 McCarthy Blvd. Milpitas, CA 90 Phone: (408)4-900 www.linear.com Fax: (408)44-007 LTC Confidential-For Customer Use Only V SYNCHRONOUS DUAL LED DRIVER WITH I C THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. SIZE N/A DATE: IC NO. LT94EUHE REV. Thursday, July, 07 SHEET OF NC NC ADDR ADDR 7 P C4 0uF 0 R 00K C SYNC/CLKOUT E PWM E C0 4.7uF 0V R M SiEDS C8 L PVIN V-V E E VIN R K CTRL E9 E0 R VIN C.uF C7 uf C 0.uF SDA PWM E JP JP ADDR ADDR L.uH WURTH 74480 R0 M D PMEG00EJ FB E4 LED- LED- L.uH WURTH 74480 C 4.7uF 0V FB C9 TP R0 4.99K R9 4.99K 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.
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 0 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 0 McCarthy Blvd. Milpitas, CA 90 Copyright 004, Linear Technology Corporation LT 087 PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 07