LT3500 Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller FEATURES DESCRIPTION n Wide Input Range: 3V to 36V Operating, The LT 3500 is a current mode PWM step-down DC/DC 40V Maximum converter with an internal 2.3A switch. The wide input range n Short-Circuit Protected Over Full Input Range of 3V to 40V makes the LT3500 suitable for regulating n 2A Output Current Capability power from a wide variety of sources, including automo- n Adjustable/Synchronizable Fixed Frequency tive batteries, 24V industrial supplies and unregulated Operation from 250kHz to 2.2MHz wall adapters. n Soft-Start/Tracking Capability Resistor-programmable 250kHz to 2.2MHz frequency n Output Adjustable Down to 0.8V range and synchronization capability enable optimization n Adjustable Linear Regulator/Driver with 13mA between ef ciency and external component size. Cycle- Output Capability by-cycle current limit, frequency foldback and thermal n Power Good Comparator with Complimentary shutdown provide protection against a shorted output. Outputs The soft-start feature controls the ramp rate of the output n Low Shutdown Current: 12A voltage, eliminating input current surge during start-up, n Thermally Enhanced 3mm 3mm DFN or 16-Pin and also provides output tracking. MSOP Package The LT3500 contains an internal NPN transistor with feed- APPLICATIONS back control which can be con gured as a linear regulator or as a linear regulator controller. n Automotive Battery Regulation n Industrial Control The LT3500s low current shutdown mode (<12A) enables n Wall Transformer Regulation easy power management in battery-powered systems. n Distributed Power Regulation 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. TYPICAL APPLICATION Dual Step-Down Converters Switching Converter Ef ciency Output Voltage Ripple 90 V IN V BST IN 6V TO 36V 85 0.47F 2.2F LT3500 6.8H V OUT1 80 V = 5V AT 1A OUT1 SW 5V AC COUPLED 1A B240A SHDN 75 2mV/DIV 42.2k SS 22F 70 0.47F FB PG 8.06k 65 PG V = 3.3V AT 1A OUT2 AC COUPLED 60 R SYNC LDRV 2mV/DIV T/ V = 12V IN V 55 53.6k C I = 0A 1k OUT2 V 330pF 24.9k OUT2 FREQUENCY = 800kHz 50 LFB 3.3V 3500 TA01c 500ns/DIV 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 40.2k 1A 8.06k 22F LOAD CURRENT (A) 3500 TA01b 3500 TA01a 3500fc 1 EFFICIENCY (%)LT3500 (Note 1) ABSOLUTE MAXIMUM RATINGS V , PG, PG Operating .................................... 40V/0.3V Operating Junction Temperature Range IN SW ............................................................................. V LT3500EDD (Note 2) .......................... 40C to 125C IN BST ................................................................ 55V/0.3V LT3500IDD (Note 2) ........................... 40C to 125C BST Pin Above SW ....................................................25V LT3500HDD (Note 2).......................... 40C to 150C LDRV, SHDN ..............................................................15V LT3500EMSE (Note 2)........................ 40C to 125C FB, LFB, R /SYNC .......................................................5V LT3500IMSE (Note 3) ........................ 40C to 125C T SS, V ......................................................................2.5V LT3500HMSE (Note 2) ....................... 40C to 150C C Storage Temperature Range ................... 65C to 150C PIN CONFIGURATION TOP VIEW TOP VIEW V 1 12 SW 1 IN NC1 16 NC16 V 2 15 SW 2 11 BST IN SHDN 3 SHDN 14 BST 3 LDRV SS 10 SS 4 13 LDRV 13 17 5 PG 12 LFB 4 LFB PG 9 V 6 11 FB C 5 FB V 8 C 7 R /SYNC 10 PG T NC8 8 9 NC9 6 7 R /SYNC PG T MSE PACKAGE DD PACKAGE 16-LEAD PLASTIC MSE 12-LEAD (3mm 3mm) PLASTIC DFN = 45C/W, = 10C/W JA JC(PAD) = 45C/W, = 10C/W JA JC(PAD) EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3500EDD PBF LT3500EDD TRPBF LCRN 12-Lead (3mm 3mm) Plastic DFN 40C to 125C LT3500IDD PBF LT3500IDD TRPBF LCRN 12-Lead (3mm 3mm) Plastic DFN 40C to 125C LT3500HDD PBF LT3500HDD TRPBF LDCY 12-Lead (3mm 3mm) Plastic DFN 40C to 150C LT3500EMSE PBF LT3500EMSE TRPBF 3500 16-Lead Plastic MSE 40C to 125C LT3500IMSE PBF LT3500IMSE TRPBF 3500 16-Lead Plastic MSE 40C to 125C LT3500HMSE PBF LT3500HMSE TRPBF 3500 16-Lead Plastic MSE 40C to 150C 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. Consult LTC Marketing for information on non-standard lead based nish parts. For more information on lead free part marking, go to: