MCU-Based Battery Charging Reference Design From Zilog

19th March 2013

Zilog Inc

ES Admin

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Whitepaper

Zilog announces its new Buck Converter Battery Charger Reference Design that employs Zilog’s Z8F042A MCU to control a step-down DC-DC converter (also known as a buck converter) that functions as a regulated power source. This buck converter battery charger hardware is capable of regulating charger output in a number of modes such as constant voltage, or constant current with set current limits.

The charger can be viewed as a complete control system. The type and capacity of the battery determines the mode of operation of the battery controller. The voltage and current setpoints are also determined by the type and capacity of the battery. All battery control loop operations can be controlled by the user via the Z8F042A MCU’s UART block, and feedback is provided in the HyperTerminal console. Additionally, LEDs provide a visual status of the charging process.

This low-cost reference design demonstrates a lithium ion battery charger consisting of a Z8F042A MCU and a buck converter. The charging process utilizes the highly accurate ADC peripheral and alternates between current and voltage monitoring which is controlled in the background software routine to allow for the UART to be processed in the main function. With the HyperTerminal GUI, the user can enter desired setvoltages and setcurrents. A proportional/integral control loop is used to charge the battery and to monitor the battery voltage after the charging process is completed. To save memory resources, the provided UART does not implement the STDIO.H libraries. Instead, a simple UART using only integer values is used.

“This battery charger reference design allows operation either via UART or an external 5–15V power supply. The advantage of this battery charger implementation is in the efficient utilization of the Zilog MCU resources, allowing for a low-cost digital power management solution that is flexible and adaptable to different batteries,” commented Steve Darrough, Zilog’s VP of Marketing.