LT3505 1.2A, Step-Down Switching Regulator in 3mm 3mm DFN FEATURES DESCRIPTION Wide Input Range: 3.6V to 36V Operating, The LT 3505 is a current mode PWM step-down DC/DC 40V Maximum converter with an internal 1.4A power switch. The wide Up to 1.2A Output Current operating input range of 3.6V to 36V (40V maximum) Resistor-Programmable Fixed-Frequency Operation makes the LT3505 ideal for regulating power from a wide from 200kHz to 3MHz variety of sources, including unregulated wall transform- Output Adjustable Down to 780mV ers, 24V industrial supplies and automotive batteries. The Short-Circuit Robust oscillator can be programmed for high frequency operation Uses Tiny Capacitors and Inductors allowing the use of tiny, low cost external components or Soft-Start it can be programmed for lower frequency operation to Low Shutdown Current: <2A maximize ef ciency. Low V Switch: 350mV at 1A CESAT Cycle-by-cycle current limit provides protection against Thermally Enhanced, Low Pro le 3mm x 3mm shorted outputs and soft-start eliminates input current DFN-8 and MSOP-8 Packages surge during start-up. The low current (<2A) shutdown mode provides output disconnect, enabling easy power management in battery-powered systems. APPLICATIONS , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Automotive Battery Regulation All other trademarks are the property of their respective owners. Industrial Control Supplies Wall Transformer Regulation Distributed Supply Regulation Battery-Powered Equipment TYPICAL APPLICATION 750kHz, 3.3V Step-Down Converter Ef ciency V OUT 90 V IN 3.3V V BOOST IN 4.2V TO 36V 1.1A, V > 5V IN 85 0.1F 10H 1.2A, V > 8V IN SHDN SW ON OFF 80 LT3505 36.5k 22pF 75 FB 70 10F 11.3k R GND V T C 65 60 V = 12V 75.0k 69.8k IN V = 3.3V OUT 55 f = 750kHz 1F 68pF SW L = 10 H 50 0 0.2 0.4 0.6 0.8 1.0 1.2 3505 TA01 LOAD CURRENT (A) 3505fc 1 EFFICIENCY (%)LT3505 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Voltage (V ) ....................................................40V Operating Temperature Range (Note 2) IN BOOST Pin Voltage ..................................................50V LT3505E .............................................. 40C to 85C BOOST Pin Above SW Pin .........................................25V LT3505I ............................................. 40C to 125C SHDN Pin ..................................................................40V Maximum Junction Temperature .......................... 125C FB Pin .........................................................................6V Storage Temperature Range ................... 65C to 150C V Pin .........................................................................3V C R Pin .........................................................................3V T PIN CONFIGURATION TOP VIEW TOP VIEW BOOST 1 8 V C BOOST 1 8 V SW 2 7 FB C 9 SW 2 7 FB 9 V 3 6 R IN T V 3 6 R IN T SHDN GND SHDN 4 5 GND 4 5 MS8E PACKAGE 8-LEAD PLASTIC MSOP DD PACKAGE T = 125C, = 40C/W, = 5C/W 8-LEAD (3mm 3mm) PLASTIC DFN JMAX JA JC EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB T = 125C, = 43C/W, = 5C/W JMAX JA JC EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3505EDD PBF LT3505EDD TRPBF LCHB 8-Lead (3mm x 3mm) Plastic DFN 40C to 85C LT3505IDD PBF LT3505IDD TRPBF LCHC 8-Lead (3mm x 3mm) Plastic DFN 40C to 125C LT3505EMS8E PBF LT3505EMS8E TRPBF LTCNX 8-Lead Plastic MSOP 40C to 85C LT3505IMS8E PBF LT3505IMS8E TRPBF LTCNY 8-Lead Plastic MSOP 40C to 125C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3505EDD LT3505EDD TR LCHB 8-Lead (3mm x 3mm) Plastic DFN 40C to 85C LT3505IDD LT3505IDD TR LCHC 8-Lead (3mm x 3mm) Plastic DFN 40C to 125C LT3505EMS8E LT3505EMS8E TR LTCNX 8-Lead Plastic MSOP 40C to 85C LT3505IMS8E LT3505IMS8E TR LTCNY 8-Lead Plastic MSOP 40C to 125C Consult LTC Marketing for parts speci ed with wider operating temperature ranges. For more information on lead free part marking, go to: