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TPS60401: Typical value for Rswitch (datasheet equation 1 and 2)

Renan Santos Adriano
Mastermind 22380 points
Part Number: TPS60401

Hi Team,

My customer is testing the TPS60401 and getting a lower output than expected. He suspected the output resistance of the converter is higher than the initial analysis. Looking to use equations 1 and 2 of the datasheet (SGLS246B, June 2004) which defines "Rswitch" as the resistance of a single MOSFET-switch inside the converter.

However, I cannot find any typical values for Rswitch in the datasheet. Could you please advise a suitable value of Rswitch? I would be happy with knowing the magnitude i.e hundreds of milliohms or tens of ohms just so that we can calculate the dominating factor of the output resistance.

Thank in advance.

Regards,

Renan 

  • 0
    TI__Mastermind 25430 points

    Hi Renan,

    The datasheet provides the formula to calculate Rswitch value. Unfortunately, it does not give any specific range. Anything beyond the datasheet specifications is not characterized.

    However you may do a reverse calculation from the output resistance formula. From equation 1, you can see that 4*2*Rswitch is the most dominant variable. 1/(fosc*Cfly) shouldn't be more than 1/1.5 Ohm. The average is about 10/15 ohm for output resistance. But again output resistance is also dependent on VIN and temperature (As seen from figures 7 and 8).

    I hope this would be helpful in making an estimate for Rswitch. Please let me know if you need further support.
    Regards,
    Febin
  • 0 in reply to Febin
    TI__Mastermind 25430 points

    Hi Renan,

    I hope my suggestion helped resolve your problem.

    I would like to close this thread now and please reach out to us for any further support.

    Regards,

    Febin