Features

• Wide Input Range:
  Operation from 3.6V to 36V
  Overvoltage Lockout Protects Circuit Through 55V Transients on Input
• 500mA Output Current Switching Regulator
• High Switching Frequency: 750kHz
• 200mA Low Dropout Linear Regulator
  1.2V to 16V Input; 0.8V to 8V Output
  310mV Dropout Voltage V_CC2 to OUT2
• Precision Programmable Undervoltage Lockout
• Short-Circuit Robust
• Internal Soft-Start
• <2μA Shutdown Current
• Small Thermally Enhanced 16-Lead (3mm × 3mm) QFN and 12-Lead MSE Packages

Typical Application

Description

The LT®3645 is a dual output regulator combining a 500mA buck regulator and a 200mA low dropout linear regulator (LDO). The wide input voltage range of 3.6V to 36V makes the LT3645 suitable for regulating power from a wide variety of sources, including 24V industrial supplies and automotive batteries. Its high operating frequency allows the use of tiny, low cost inductors and capacitors, resulting in a very small solution.

Cycle-by-cycle current limit and frequency foldback provide protection against shorted outputs. Soft-start and frequency foldback eliminate input current surge during start-up.

The linear regulator operates from the V_CC2 pin at voltages down to 1.2V. It supplies 200mA of output current with a typical dropout voltage of 310mV.

Other features of the LT3645 include a <2μA shutdown, short circuit protection, soft-start and thermal shutdown. The LT3645 is available in the thermally enhanced 16-lead (3mm × 3mm) QFN package, or a 12-lead MSE package.