LT3957 Boost, Flyback, SEPIC and Inverting Converter with 5A, 40V Switch FEATURES DESCRIPTION n Wide Input Voltage Range: 3V to 40V The LT 3957 is a wide input range, current mode DC/DC n Single Feedback Pin for Positive or Negative converter which is capable of generating either positive Output Voltage or negative output voltages. It can be con gured as either n Internal 5A/40V Power Switch a boost, yback, SEPIC or inverting converter. It features n Current Mode Control Provides Excellent Transient an internal low side N-channel power MOSFET rated for Response 40V at 5A and driven from an internal regulated 5.2V n Programmable Operating Frequency (100kHz to supply. The xed frequency, current-mode architecture 1MHz) with One External Resistor results in stable operation over a wide range of supply n Synchronizable to an External Clock and output voltages. n Low Shutdown Current < 1A The operating frequency of LT3957 can be set with an n Internal 5.2V Low Dropout Voltage Regulator external resistor over a 100kHz to 1MHz range, and can n Programmable Input Undervoltage Lockout with be synchronized to an external clock using the SYNC pin. Hysteresis A minimum operating supply voltage of 3V, and a low n Programmable Soft-Start shutdown quiescent current of less than 1A, make the n Thermally Enhanced QFN (5mm 6mm) Package LT3957 ideally suited for battery-powered systems. The LT3957 features soft-start and frequency foldback APPLICATIONS functions to limit inductor current during start-up. n Automotive L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and No R and ThinSOT are trademarks of Linear Technology Corporation. SENSE n Telecom All other trademarks are the property of their respective owners. Patents pending. n Industrial TYPICAL APPLICATION High Ef ciency Output Boost Converter Ef ciency vs Output Current 10H V OUT 100 V IN 24V V = 12V IN 4.5V TO 16V 600mA 10F 10F 95 200k V SW s 2 IN EN/UVLO GND 90 95.3k LT3957 85 SGND SENSE1 226k SYNC SENSE2 80 FBX INTV RT SS VC 15.8k 75 CC 41.2k 6.8k 0.33F 4.7F 70 300kHz 0 400 500 600 100 200 300 22nF OUTPUT CURRENT (mA) 3957 TA01b 3957 TA01a 3957f 1 EFFICIENCY (%)LT3957 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW V , EN/UVLO (Note 5), SW ......................................40V IN INTV ......................................................V + 0.3V, 8V CC IN SYNC ..........................................................................8V 36 35 34 33 32 31 30 VC, SS .........................................................................3V NC 1 28 INTV CC RT 1.5V NC V ............................................................................................... 2 27 IN SENSE1, SGND .................. Internally Connected to GND SENSE2 3 SGND 37 SGND 4 25 EN/UVLO SENSE 2 .................................................................. 0.3V 24 SGND FBX ................................................................. 6V to 6V SENSE1 6 23 SGND Operating Junction Temperature Range (Note 2) .................................................. 40C to 125C SW SW 8 21 SW 38 Maximum Junction Temperature .......................... 125C SW 9 20 SW Storage Temperature Range .................. 65C to 125C NC 10 12 13 14 15 16 17 UHE PACKAGE 36-LEAD (5mm s 6mm) PLASTIC QFN T = 125C, = 42C/W, = 3C/W JMAX JA JC EXPOSED PAD (PIN 37) IS SGND, MUST BE SOLDERED TO SGND PLANE EXPOSED PAD (PIN 38) IS SW, MUST BE SOLDERED TO SW PLANE ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3957EUHE PBF LT3957EUHE TRPBF 3957 40C to 125C 36-Lead (5mm 6mm) Plastic QFN LT3957IUHE PBF LT3957IUHE TRPBF 3957 36-Lead (5mm 6mm) Plastic QFN 40C to 125C Consult LTC Marketing for parts speci ed with wider operating temperature ranges. *The temperature grade is identi ed by a label on the shipping container. For more information on lead free part marking, go to: