Switching regulator optimizes battery charger efficiency

Linear Technology Corp. has developed the LT3653, a 1.2A, 1.5MHz monolithic current mode step-down switching regulator with a programmable output current limit.

The LT3653 is typically used with battery charger power path controllers to pre-regulate the output and optimize battery charger efficiency. Its wide operating input voltage of 7.5- to 30V makes the LT3653 suitable for a variety of input sources including unregulated 12V wall adapters, 24V industrial supplies and Firewire as well as automotive applications. Onboard input overvoltage lockout protects the device through input transients as high as 60V, such as those commonly found in automotive applications.

The LT3653's control pin, VC, is available for external battery tracking, known as Bat-Track control. This function keeps the output voltage only 300mV above the Li-ion battery voltage, which minimizes thermal issues while simultaneously optimizing charger efficiency. Similarly, the LT3653 offers an adjustable output current limit which can be set between 400mA and 1.2A via an external resistor.

In addition, the device does not allow reverse discharge from the battery to VIN, eliminating the need for a blocking FET. It also utilizes a 1.5MHz oscillator, internal compensation and an internal boost diode to minimize the overall solution footprint. Combined with a 2mm x 3mm DFN package, the LT3653 offers a very compact high voltage input regulator for battery charger applications.

The LT3653EDCB pricing starts at $2.50 each for 1,000-piece quantities. An industrial grade, the LT3653IDCB is tested and guaranteed to operate from a -40¡ãC to 125¡ãC operating junction temperature and are priced at $2.88 each for 1,000-piece quantities. Both versions are available from stock.