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BQ25713: About FET Selection

NAIM OTHMAN
Intellectual 270 points
Part Number: BQ25713
Other Parts Discussed in Thread: CSD17551Q3A

Hi TI Team,

I would like to confirm about FET selection for BQ25713 buck-boost circuit.

We need to change FET from AON7934 to FDMC007N30D .

The gate voltage rating decrease from 20V → 12V.

From the datasheet page 73, it says the gate drivers are internally integrated into the IC with 6 V of gate drive voltage.

So I assume there will be no problem. Can you kindly confirm?

Design parameters

Vin  = 15V ~ 20V

Vout = 10V ~ 17V

Pout  max = 45W

Best Regards

Naim

  • 0
    TI__Expert 5330 points

    Hi Naim,

    You are correct.  The low-side FET is driven from REGN (6V nominal) and GND.  The high-side FET is driven from BTST (SW + REGN charge pump) and SW, so the gate drives are always driving G-S differential voltage on these FETs to either REGN voltage or 0V.  This is confirmed by the ABSMAX ratings for HIDRV and LODRV pins in the datasheet.  LODRV ABSMAX is -0.4 to 7V (GND referenced) and HIDRV - SW has same range.  (These are the absolute max differential voltage that these pins were designed to support, so confirms that these are max ranges we expect during normal operation.)

    Based on this, I do not see an issue with the change to +/-12V G-S rating.  That said, our EVM is validated with the CSD17551Q3A TI NexFET, which has +/- 20V G-S rating.  As with any deviation from our validated solution, please be sure to validate the design change.

    Regards,

    Steve