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BQ25731: Thoughts on Changing FETs from CSD17551Q3A to CSD17579Q3A

Part Number: BQ25731
Other Parts Discussed in Thread: CSD17551Q3A, CSD17579Q3A, CSD17578Q3A

We're looking to update FETs to reduce thermals and power consumption on board. Are there any concerns with changing from the CSD17551Q3A  to the  CSD17579Q3A FETs?

The specs look better in general but I notice the gate and input capacitance is a little different.


  • Hi Nick,

    The two FETs that you named are very similar, so it should be fine to switch from the CSD17551Q3A to the CSD17579Q3A.

    However, I'm not sure if this will improve the power consumption. The CSD17579Q3A has lower Qg, but higher Rdson. Therefore, I would expect the switching losses to be lower, but the conduction losses to be higher. You will need to test the efficiency on your own board using both FETs in order to determine which FET provides better performance.

    Another option you could consider is the CSD17578Q3A, which has the lowest Rdson out of the 3 FETs, but the highest Qg. All of these FETs are pin-to-pin compatible, so you can replace the FETs on the same board when testing the efficiency.

    Best regards,