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TPS2640: About overcurrent behvier

Jimmy WANG
Genius 3585 points
Part Number: TPS2640

Tool/software:

Hi team,

My customer found some issues here. I can not explain it.  Could you provide your suggestion?

The schematic and waveform as below.

Test condition.

The original current limit setting is 0.8A. It's a Fan power as input application.

Next step: The customer blocked the fan on purpose then the input current will increase.

From the datasheet if Io>ICB then the timer will count 4ms.

It seems that the overcurrent does not exceed 4ms. Why does the voltage drop?

CH1 = Vo

CH3= Fan speed (Frequency Generator)

CH4= Input current

  • 0
    Genius 3585 points

    Hi team,

    Could you reply it? thanks 

  • 0 in reply to Jimmy WANG
    TI__Genius 16301 points

    Hello Jimmy,

    I can't read the waveform clearly attached.

    What's the input current per division value.

    When Vout drops, does it turn off the FAN. because I can't see FAN speed after last one.

    Thanks 

    Amrit 

  • 0 in reply to Amrit Jit
    Genius 3585 points

    Hi Amrit,

    Input current is 500mA per division. Due to Vo drop so some external circuit detect then shut down the fan.

    So customer's question is seems no over current event occur why Vo drop? Thanks 

    Another question is If the peak current reaches the set value, the Timer starts counting for 4ms.
    If it exceeds 4ms, turn off the MOSFET 

  • 0 in reply to Jimmy WANG
    TI__Genius 16301 points

    Hello Jimmy,

    Jimmy WANG said:
    Another question is If the peak current reaches the set value, the Timer starts counting for 4ms.
    If it exceeds 4ms, turn off the MOSFET 

    Yes, Correct. That's the circuit breaker action.

    Is there any other fault which could be registering? Can you prove VIN and FLT pin as well.

    Thanks

    Amrit