This application note describes the design of an efficient and low-cost single-battery power supply for notebook and palmtop computers. The system uses the high-efficiency LT1432 dual-channel switching regulator to provide 5V and 3.3V power to the circuits.
The document introduces the Linear Technology LT1432, a control chip designed to operate with the LT1170 or LT1270 family of switching regulators. It is intended for creating highly efficient 5V or 3.3V step-down (buck) converters suitable for notebook and palmtop systems where small size, light weight, and high efficiency are mandatory. The text highlights that the LT1432 allows the power switch to be floated as required in a step-down converter while providing full saturation for maximum efficiency.
In normal switching mode, the standby power loss is about 60mW.
The input supply current is typically 1.3mA in this mode.
Pulling the mode pin above 2.5V forces the entire regulator into micropower shutdown, drawing less than 20µA.