Buck-boost converter extends usable life of Li-ion batteries

17th October 2014
Siobhan O'Gorman

Designed to prolong battery life in single-cell Li-ion battery applications where the output voltage is within the battery voltage range, the XC9306 converter has been released by Torex Semiconductor. When discharged, a Li-ion battery's operating voltage declines to the point that it can no longer power it's load. The synchronous buck-boost converter boosts the output voltage of the battery, extending it’s usable life.

By using the remaining charge of the Li-ion battery, the converter extends it’s life more efficiently. Reducing the overall mounting area by as much as 50%, the XC9306 uses a 6MHz switching frequency which allows for a smaller inductor and capacitors. To obtain maximum efficiency, the buck-boost converter operates in fixed frequency PWM mode (MODE pin: “High”) using synchronous rectification. To maintain high efficiency over a wide load current range, the converter can be switched over to Power Save mode (MODE pin: “Low”) at low load currents.

The device has a 2.5-5.5V voltage range and allows input current to be limited to a typical value of 3.1, 1.3 or 0.49A. Maximum output currents of 1.2 (Buck PWM Mode) and 0.8A (Boost PWM Mode) are supported by the buck-boost converter.

Using an external resistor divider in the range 0.8-5.0V, the output voltage can be programmed. For applications that require a lower chipset core voltage during standby, the VSEL pin can be used to select a second output voltage level. Measuring 2.15x1.94x0.625mm, the XC9306 synchronous buck-boost converter is offered in the WLP-20-01 package.

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