3.3V High Efficiency Step-Down Switching Regulator Controller

OBSOLETE: For Information Purposes Only. Contact Analog Devices for Potential Replacement.

The LT1432-3.3 is a control chip designed to operate with the LT1171/LT1271 family of switching regulators to make a very high efficiency 3.3V step-down (buck) switching regulator. A minimum of external components is needed.

Included is an accurate current limit which uses only 60mV sense voltage and uses “free” PC board trace material for the sense resistor. Logic controlled electronic shutdown mode draws only 15µA battery current. The switching regulator operates down to 4.5V input.

The LT1432-3.3 has a logic controlled BurstMode operation to achieve high efficiency at very light load currents (0mA to 100mA) such as memory keep-alive. In normal switching mode, the standby power loss is about 30mW, limiting efficiency at light loads. In Burst Mode operation, standby loss is reduced to approximately 11mW. Output current in this mode is typically in the 5mA to 100mA range.

The LT1432-3.3 is available in 8-pin SO and PDIP packages. The LT1171/LT1271 is also available in surface mount DD packages.

Applications

* Laptop and Palmtop Computers

* Portable Data-Gathering Instruments

* OBSOLETE: For Information Purposes Only. Contact Analog Devices for Potential Replacement.

* Accurate Preset 3.3V Output

* Up to 87% Efficiency

* Optional Burst Mode™ Operation for Light Loads

* Can Be Used with Many LTC Switching ICs

* Accurate Ultra-Low-Loss Current Limit

* Operates with Inputs from 4.5V to 30V

* Shutdown Mode Draws Only 15µA

* Uses Small 30µH Inductor