BQ76200: How to select BOOT capacitor value

Dillen Chen

Part Number: BQ76200

Hi Team,

We want to know how to select BOOT capacitor value. If we calculate the value based on the formula C=Qgtotal/ΔV, ΔV=VDD-UVLO, then we choose 10 times to the calculated value. This boot capacitor can not drives normally. The waveform as follow: red line is Vgs, blue line is Vboot.

If we set the boot capacitor to be particularly large， what influence will it happen? BTW, can you confirm whether we can combine two BQ76200 DSG or CHG to Improve driving ability？

over 2 years ago

0 Luis H. S. over 2 years ago

TI__Mastermind 42060 points

Hello Dillen,

There is a FET capacitance vs. charge-pump capacitor values that may be useful to find the right sized capacitor there.

You can find it in Section 6 VDDCP Capacitance Reference Table of the FET Configurations for the bq76200 High-Side N-Channel FET Driver application note. There's also discussion on the charge-pump in Section 2.1 Charge Pump of the bq76200 Beyond the Simple Application Schematic application note.

If the boot capacitor is too large, the biggest downside would become that the FET switching may be too slow, see E2E thread below:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/847260/bq76200-bq76200-charge-pump-capacitor

Best Regards,

Luis Hernandez Salomon

Power management

Power management forum

BQ76200: How to select BOOT capacitor value