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TPS25940EVM-635: TPS25940

Part Number: TPS25940EVM-635
Other Parts Discussed in Thread: TPS25940

Hi,

I'm trying to implement the TPS25940EVM-635 as a super capacitor charger. Concerned about that I have few questions.

I used C_ss or C_dVdT approx 15uF and in general it's working as expected. However there is a delay between the power applying and starting of charging (indicated with a red ring)

I noticed that this delay is depending on the used C_dVdT (C_ss) value. How could I reduce the delay?

Thanks.

  • Hi Tonis,

    Yes, your observation is correct. The startup selay is dependent on the C_dVdT (C_ss) value used. 

    As you know the C_ss cap decides the output ramp rate which is in actually realized by controlling the slew rate of the internal gate signal to the internal FET.

    Untill the gate voltage reaches the Vgs threshold of the internal FET, you wouldn't see any output rising as per the Mosfet functionality.

    In order to avoid this, you can use the current limit feature of TPS25940 instead of Cdvdt based startup. For example, set the current limit to 1A without any Cdvdt cap. You will see that the device starts up with 1A current limit without any delay at startup. 

  • Hi,

    (I asked about this question already in another thread, but haven't heard anything about it already two days)

    I removed the C_ss capacitor and remvoed the current limit jumper. Like this the current should be limited to ~2A.

    But when I do the test it doesn't work. The output is just blocked:

    Here I used the C_ss capacitor, but the result is the same. What could cause the Error mode?

    Thanks

  • Hi Tonis,

    Below is the link to your other query. It has been answered the same day. Please let me know if you are facing issues in viewing the thread. 

    https://e2e.ti.com/support/power-management/f/196/t/892758