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CSD16570Q5B: Why CSD16570Q5B is not designed for switching applications?

Ocean Chen
Prodigy 70 points
Part Number: CSD16570Q5B
Other Parts Discussed in Thread: CSD17573Q5B

Hi Pro. :

I am looking for a low Rds(on) MOS to implement MOS relay. 

But see the warring description in datasheet. Why CSD16570Q5B is not designed for switching applications? 

The MOS as relay in my design, operation frequency <1KHz. Bypass about DC 25A current.

Can CSD16570Q5B be used?  Could I have recommend solution?

Thank you.

  • 0
    TI__Mastermind 29525 points

    Hi Ocean,

    Thank you for your interest in TI MOSFETs. The CSD16570Q5B is optimized for hot swap and OR'ing applications where the device is turned on and left on for long periods of time to conduct significant current to the downstream load, typically DC-DC converter(s). The part was therefore designed for lowest rds(on) to minimize conduction loss. There are a couple reasons why it is not recommended for switch-mode applications: the gate charge and capacitance are very large (250nC max at VGS = 10V) making it difficult to drive efficiently and the QGD:QGS charge ratio > 1 which makes it susceptible to CdV/dt induced turn-on in half bridge configurations such as a synchronous buck converter. It may be possible to use this FET in a low frequency switching application like yours but unfortunately we have no data for how it will perform. TI has not tested the CSD1657Q5B in this type of application.

    You can try an alternative device such as CSD17573Q5B. The on resistance is higher but it is better suited to switching applications. In any case, your board can be laid for the 5x6mm SON package and you can test multiple devices such as the CSD17573Q5B and the CSD16570Q5B to see how they perform in your application.