LT3741/LT3741-1 High Power, Constant Current, Constant Voltage, Step-Down Controller FEATURES DESCRIPTION n Control Pin Provides Accurate Control of Regulated The LT 3741 and LT3741-1 are fixed frequency synchro- Output Current nous step-down DC/DC controllers designed to accurately n 1.5% Voltage Regulation Accuracy regulate the output current at up to 20A. The average current- n 6% Current Regulation Accuracy mode controller will maintain inductor current regulation n 6V to 36V Input Voltage Range over a wide output voltage range of 0V to (V 2V). The IN n Wide Output Voltage Range Up to (V 2V) regulated current is set by an analog voltage on the CTRL IN n Average Current Mode Control pins and an external sense resistor. Due to its unique n <1A Shutdown Current topology, the LT3741 is capable of sourcing and sinking n Up to 94% Efficiency current. If sinking current is not required, or for parallel n Additional Pin for Thermal Control of Load Current applications, use the LT3741-1. The regulated voltage and n overvoltage protection are set with a voltage divider from Thermally Enhanced 4mm 4mm QFN and 20-Pin the output to the FB pin. Soft-Start is provided to allow a FE Package gradual increase in the regulated current during startup. The switching frequency is programmable from 200kHz to APPLICATIONS 1MHz through an external resistor on the RT pin or through n the use of the SYNC pin and an external clock signal. General Purpose Industrial n Super-Cap Charging Additional Features include an accurate external reference n Applications Needing Extreme Short-Circuit Protec- voltage for use with the CTRL pins, an accurate UVLO/EN tion and/or Accurate Output Current Limit pin that allows for programmable UVLO hysteresis, and n Constant Current or Constant Voltage Source thermal shutdown. All registered trademarks and trademarks are the property of their respective owners. Protected by U.S. Patents including 7199560, 7321203 and others pending. TYPICAL APPLICATION 10V/20A Constant Current, Constant Voltage Step-Down Converter V vs I V IN OUT OUT EN/UVLO EN/UVLO V IN 14V TO 36V 12 RT 1F 100F SYNC 82.5k HG 10 LT3741 220nF V REF CBOOT 2.2H V 10nF 2.5m OUT 8 10V SW 20A CTRL1 6 V CC INT VC 22F 39.2k 4 R LG HOT 150F 45.3k 2 5.6nF GND V = 18V 2 IN + CTRL2 SENSE V = 10V OUT 88.7k I = 20A SENSE LIMIT 0 R NTC SS FB 0 2 4 6 8 10 12 14 16 18 20 22 10nF 12.1k I (A) OUT 3741 TA01b 3741 TA01a 37411fg 1 For more information www.linear.com/LT3741 V (V) OUTLT3741/LT3741-1 ABSOLUTE MAXIMUM RATINGS (Note 1) V Voltage ................................................................40V RT Voltage ..................................................................3V IN EN/UVLO Voltage ........................................................6V FB Voltage ...................................................................3V V Voltage ...............................................................3V SS Voltage ..................................................................6V REF CTRL1 and CTRL2 Voltage ..........................................3V V Voltage ...........................................................6V CC INT + SENSE Voltage ........................................................40V SYNC Voltage ..............................................................6V SENSE Voltage ........................................................40V Storage Temperature Range .................. 65C to 150C VC Voltage ..................................................................3V Lead Temperature (Soldering, 10 sec) SW Voltage ...............................................................40V TSSOP ..............................................................300C CBOOT ......................................................................46V PIN CONFIGURATION TOP VIEW TOP VIEW V 1 20 LG CC INT GND 2 19 CBOOT 20 19 18 17 16 V 3 18 SW IN EN/UVLO 1 15 HG EN/UVLO 4 17 HG V 2 14 GND REF V 5 16 GND REF 21 21 CTRL2 3 13 SYNC GND GND CTRL2 6 15 SYNC GND 4 RT 12 GND 7 14 RT CTRL1 GND 5 11 CTRL1 8 13 VC 6 7 8 9 10 SS 9 12 SENSE + FB 10 11 SENSE FE PACKAGE 20-LEAD PLASTIC TSSOP UF PACKAGE 20-LEAD (4mm 4mm) PLASTIC QFN T = 125C, = 38C/W JMAX JA EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB T = 125C, = 37C/W JMAX JA EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB