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BQ24780S: Low-side gate control rises slowly

Antony Lin
Genius 13480 points
Part Number: BQ24780S

Hi,

During charging behavior test we found low-side gate rises a little bit slower like below.  Would there be any concern or risk for this?

Thanks.

Antony

Case1: Charging current is 0.5A (no system load)

CH1: Low side gate   CH3: SW  

Case2: 

Charging current is 5.5A (no system load)

CH1: Low side gate   CH3: SW 

  • 0
    TI__Expert 5330 points

    Hi Anthony,

    The most important parameter is the amount of time it takes the SW node to transition.  If it takes too long, then you will loose efficiency or even burn up the FET.

    Here is a capture from the EVM:

    It takes about 20 nSec for the SW node to transition and about 40 nS total for the gate to transition.  Your captures are slower than that, so you will have lower efficiency and possibly a thermal issue.

    Have you checked the gate charge of the FETs you are using against the EVM? 

    Regards,

    Steve