Charge pump capacitor value estimation

[B-hafedh]

How do you estimate the charge pump capacitor value ? 416nF10=640nF

[martinjaeger]

That rule of thumb with a factor of 10 times gate capacitance was mentioned in the reference manual or one of the other documents provided by TI.

[B-hafedh]

Thank you, but there is no information about it in bq76952 datasheet, can you provide me the document please. and i have another question: what is the role of the schottky diode & zener diode connected to VC0, i thought they are used for reverse polarity protection, but you already used a schottky diode connected to VC16.

[martinjaeger]

It was not necessarily the datasheet. There are lots of documents for this chip provided by TI, I don't remember which one it was.

In any case you can also estimate the value yourself. It is a trade-off between startup-time (faster if capacitance is lower) and voltage drop during switch-on event (lower if capacitance is higher).