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LibreSolar / bms-c1

16s / 100A Battery Management System
https://libre.solar/bms-c1/manual/
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Charge pump capacitor value estimation #29

Open B-hafedh opened 2 years ago

B-hafedh commented 2 years ago

CP1

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

martinjaeger commented 2 years ago

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 commented 2 years ago

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 commented 2 years ago

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).