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TPS25982: Skipping cycle on start up

GY Hanna
Prodigy 10 points
Part Number: TPS25982


In my design, the input power cycles on and off.

While the device works as expected, we have seen a skipped cycles. That's the output is off.

In this scope picture, the green line is the input, Blue is the output and yellow is the PG.

The circuit design is as follow:

The input voltage is 12VDC.

Current consumption in less than 1A

Appreciate your input/help.

  • 0
    TI__Guru* 79181 points

    Hi,

    Thanks for reaching out. What is capacitance value  at efuse output ? Is there any other load at efuse output during startup?

    What is the value of CDVDT cap? It would be helpful if  you could also  probe current through efuse .

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 10 points

    The CDVDT is open (no CAP)

    the output is an LED light

    No other load at the output.

  • 0 in reply to GY Hanna
    TI__Guru* 79181 points

    Hi ,

    It looks that device is hitting thermal shutdown in skipped cycle. During startup power dissipation is high across the device and can cause junction temperature to cross thermal shutdown temperature and turn off before device fully turn on. 

    Increasing start up time helps in reducing power dissipation. To increase startup time, CDVDT has to be increased.

    Please try with different cdvdt cap values(2.2nf,4.7nf)  in increasing order and see at what cap value this issue is gone.

    Can you tell more about led load? How much current it draws during startup?

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Guru* 79181 points

    Hi,

    Closing thread for now. Let me know if there is further query.

    Regards

    Kunal Goel