ZHCSCE2I October 2013 – March 2022 BQ76920 , BQ76930 , BQ76940
PRODMIX
The BQ769x0 devices are powered through the BAT and REGSRC pins but the BQ76930 and BQ76940 have additional ‘Power’ pins to provide the power to the entire device in the higher cell configurations.
The use of Rf and Cf connected to the BAT pin, noted in the typical application diagrams, are required to filter system transients from disturbing the device power supply. These components should be placed as close as to the IC as possible.
Additionally, for the BQ76930 and BQ76940 there are additional requirements to ensure a stable power supply to the device. The REGSRC pin is powered through a source follower circuit where the FET is used to provide current for REGSRC from the battery positive terminal while reducing the voltage to a suitable value for the IC. The FET also dissipates the power resulting from the load current and dropped voltage external to the IC and care should be taken to ensure the correct dissipation ratings are specified by the chosen FET.
The BQ76920 does not use a FET because the battery voltage is within the REGSRC range.
More information on this topic is available in the BQ769x0 Family Top Design Considerations Application Report.