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BQ24650: Abnormal charge using 10A or 4A

Cherry Zhou
Mastermind 22235 points
Part Number: BQ24650

Hi team,

Here's an issue from the customer may need your help:

The circuit is designed as follows:

Change current sense resistor to 20mΩ and inductance to 10uH, charging is fine.  Change the current sense resistor to 4mΩ and inductance to 3.3uH, charging is not good.  The status 1 light blinks at a certain frequency, and the circuit appears to be switching all the time, with an input power supply of 27.2V, 2.1A, and an inductor saturation current of 14A.

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Mastermind 37105 points

    Hello Cherry,

    I notice one thing right of the bat. You have an input supply capable of 57.12 W. However you are requesting a charge power of maximum 25.2 V x 10 A or 252 W. Even at LOWV of 18.6 V, you are still requesting 186 W of output power. In other words your input cannot support your output. As a result, the input voltage may be dropping below the MPPSET pin stopping charge only to rise again and then fail again. Your chosen MPPSET voltage it appears is 6.84 V. At this voltage the input will limit the charge current to keep this pin at 6.84 V.

    Regards,

    Mike Emanuel