BQ24780S: Reason for Gate-Source and Gate-Drain capacitance for Q1 and Q2?

Biswadeep Indu33

Part Number: BQ24780S
Other Parts Discussed in Thread: CSD17308Q3

The EVM Schematic recommends 1nF and 47nF capacitor at C12 and C13. Whereas the MOSFET, CSD17308Q3, Ciss = 1000pF and Coss= 150pF. What is the reason for C12 and C13?

over 6 years ago

0 Steve Preissig over 6 years ago

TI__Expert 5330 points

These capacitors slow the turn-on of the FET, providing a soft start that limits the inrush current when an adapter is hot plugged. Though not based on BQ25780s EVM, the following app note provides some details on a similar circuit that may provide further insight:
www.ti.com/.../slva156.pdf

Regards,
Steve

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BQ24780S: Reason for Gate-Source and Gate-Drain capacitance for Q1 and Q2?