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TPS630250: 10uF input capacitor operation

K. Sasaki14
Guru 10200 points
Part Number: TPS630250

There is typical application schematic on datasheet P.13.
Have you observed device operation with this schematic?

Our customer tested with TPS630250EVM-668 at the following condition. And they removed C5 (100uF input capacitor) of EVM.
Vin: 3.3V
Vout: 3.3V
Iout: 2A

As a result, output voltage was not stable because input voltage swung.
Can TPS630250 operate with only 10uF 6.3V input capacitor at the above condition?

Best Regards,
Kohei Sasaki

  • 0
    TI__Expert 8420 points
    The 100uF capacitor helps to have a clean supply to the EVM, here is a blogpost explaining the purpose of it on an EVM:

    e2e.ti.com/.../what-is-that-giant-tantalum-cap-on-the-input-of-the-evm

    On the customer application, with a clean input on VIN, the big bulk capacitor is not needed.
  • 0 in reply to Sabrina
    Guru 10200 points

    Sabrina-san,

    I tested with TPS630250EVM, and I observed input voltage waveform.
    Test condition was 3.3Vin, 3.3Vout, 2A load.
    I took the following waveform. The input voltage swung when 2A load flowed.
    From this result, should we judge more input capacitors are needed? Or do you have any idea about the cause of this swing?

    TEK00000.TIF

    Best Regards,
    Kohei Sasaki

  • 0 in reply to K. Sasaki14
    TI__Expert 8420 points

    This issue is related to the measurement setup. the 100 uF capacitor helps to provide this clean supply to the power stage. If you remove it please make sure you you provide a clean supply, which can be a challenge. The different options are : try to use shorter cables to connect the power supply to the EVM, connect a big capacitor ( for example 5mF capacitor) at the end of the cable connecting the power supply to the EVM.

    What is the end application? Could you share the business opportunity through private message?

  • 0 in reply to Sabrina
    Guru 10200 points

    Sabrina-san,

    Please e-mail to me, my adress is "sasaki-k@clv.macnica.co.jp".

    I tried shorter cable, however it didn't improve. I used the "E3632A" DC power supply of HP.
    Is this cause due to cable inductance?
    About big capacitor, where should we connect to? DC power supply side of cable? or EVM side?
    Our customer is concerned that 10uF is not enough for input capacitor on their system. Our customer is testing with TPS630250EVM too.


    Best Regards,
    Kohei Sasaki