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TPS43060: Rated Power of RCHARGE

Shinichi Inoue
Guru 19941 points
Part Number: TPS43060

Dear Specialists,

My customer is considering TPS43060 and has a question.

I would be grateful if you could advise.

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I have a question about the rating of Rcharge

I understand Rcharge is for limiting the current charging the bootstrap capacitor,

A current of VCC/Rcharge flows when the capacitor is not charged at all. It will be 7.5V/4.7ohm= 1.6A, but it doesn't always flow. It just flows a few times.

When switching is performed, I think that the current does not flow so much because the charge consumed by switching is additionally charged.

The value obtained by multiplying that current by the switching frequency is the current value.

After all, how many watts should Rcharge power rating be?

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I appreciate your great help in advance.

Best regards,

Shinichi

  • +1
    TI__Mastermind 19420 points

    Hi Shinichi,

    Thanks for using the e2e forum.
    I agree with your consideration. There will be one initial charge up when the device is powered up, and then there will be the current to drive the switches, which is supplied by VCC as well.

    Overall, I would not assume the power requirements for the resistor are high, so a rating of e.g. 0.1W, which is common for 0603 packages, should be fully sufficient.
    For TPS43060, this charge resistor at VCC is optional. If a slow down of the gate charge is desired, the same resistor can be implemented as gate resistor directly at the FET. This way, there is no risk of the internal VCC voltage cranking.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Guru 19941 points

    Hi Niklas,

    Thank you for your reply.

    I understand 0.1W is enough for power rating of Rcharge.

    I'll share this with the customer.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi