Datasheet LT3505 (Analog Devices)

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 oscil ator 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: <2µA maximize effi ciency. ! Low VCESAT Switch: 350mV at 1A Cycle-by-cycle current limit provides protection against ! Thermally Enhanced, Low Profi 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 (<2µA) shutdown mode provides output disconnect, enabling easy power APPLICATIONS management in battery-powered systems. , 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 Effi ciency
V VOUT IN 90 4.2V TO 36V VIN BOOST 3.3V 0.1µF 1.1A, VIN > 5V 10µH 85 1.2A, VIN > 8V ON OFF SHDN SW 80 LT3505 36.5k 22pF 75 FB 70 11.3k 10µF RT GND VC EFFICIENCY (%) 65 75.0k 69.8k 60 VIN = 12V VOUT = 3.3V 1µF 68pF 55 fSW = 750kHz L = 10 H 50 0 0.2 0.4 0.6 0.8 1.0 1.2 3505 TA01 LOAD CURRENT (A) 3505fc 1