BQ25710: MOSFET selection from gate driver

Kazuto Tatsumi

Part Number: BQ25710
Other Parts Discussed in Thread: CSD17551Q3A, CSD17578Q3A

Hi,

The datasheet describes how to select Buck-Boost MOSFET in terms of switching loss, but the ability of gate driver is not mentioned. Do you have any recommendation value to choose Buck-Boost MOSFET from Ciss or perspective of gate drive ability like BATFET below?

>The BATDRV pin is only able to drive a battery MOSFET with Ciss lower than 5nF. The Ciss in the range of 1nF~3nF is recommended.

Regards,
Kazuto

over 3 years ago

0 Angelo Zhang87 over 3 years ago

TI__Genius 11850 points

Hi Kazuto,

We recommend using switching FETs with low Ciss as well. For example, the CSD17551Q3A FETs that are used on the EVM have a typical Ciss of 1050 pF. If the Ciss is large, then the switching FETs will have slower turn on/turn off times, which will reduce the efficiency.

Some of the key considerations when selecting the switching FETs are to avoid very large Rdson, Qg, Qgd, Ciss, and Vgs(th). These parameters all affect the turn on speed of the FET, as well as the resistance level when the FET is on. We recommend using either the CSD17551Q3A FETs (used on the EVM), or the newer CSD17578Q3A (which has lower Rdson). It is possible to use other FETs as well, but please use these two TI FET suggestions as a reference point and do not deviate too far from them.

Best regards,

Angelo

0 Kazuto Tatsumi over 3 years ago in reply to Angelo Zhang87

TI__Intellectual 2820 points

Hi Angelo, got it. thanks!

Regards,
Kazuto

0 Kazuto Tatsumi over 3 years ago in reply to Angelo Zhang87

TI__Intellectual 2820 points

Hi Angelo,

The customer needs to know the gate drive ability of REGN. Could you share V-I curve of REGN?

If the calculation below is appropriate to get the drive current, V_regn at 96mA must be higher than V_th, correct?

I_drv = Qg * [number of MOSFET] *Fsw
= 30nC * 4 * 800kHz
= 96mA

(All of FETs are not turn on at the same time, so number of MOSFET should be *2?)

Regards,

Kazuto

0 Kazuto Tatsumi over 3 years ago in reply to Kazuto Tatsumi

TI__Intellectual 2820 points

The question above has been posted as a new thread below.

https://e2e.ti.com/support/power-management/f/196/t/977900

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BQ25710: MOSFET selection from gate driver