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TPS62067-Q1: Regarding Rise & Fall time & over current limit protection of IC

Vignesh T
Prodigy 40 points
Part Number: TPS62067-Q1

We are using this IC to generate 1.5V & 1.8V individually from 3.3.V.

Need the rise time & fall time of the internal FETs to calculate the switching loss.

Also, if there is short at the output side, will the IC retry after certain time. Or will the IC latch off? Based on datasheet, As soon as the switch current-limits are met and the output voltage falls below 1/3 of the nominal output voltage because of overload or short circuit condition, the foldback current-limit is enabled. In this case the switch current-limit is reduced to 1/3 of the nominal value ILIMF. Will this operational cycle repeat? Or, will it stop after the first iteration?

Thank You,

Vignesh T

  • 0
    TI__Genius 13440 points

    Hi Vignesh,

    Switching loss depends on the load current and the operating conditions. There is no data available for the rise and fall time but the expected typical value would be around 8ns.

    Short circuit, protection try to protect the device and the operation will continue till the output voltage exceeds 1/3 of the nominal output voltage.

    Best regards,

    Tanvee

  • 0 in reply to Tanvee
    Prodigy 40 points

    HI,

    Thanks for the response.

    With regard to short & over current protection, we are trying to analysis what will be the power dissipation of the IC during overcurrent or short fault to ensure the IC is not damaged.

    Is the thermal shutdown feature enough to protect the IC?

    Also the recommended junction temperature is provided in datasheet as 125C but absolute is 150C. So what will happen if the IC is heated upto 135C, will the IC be damaged or will it function improperely.

    Thanks!

    Vignesh T

  • 0 in reply to Vignesh T
    TI__Genius 13440 points

    Hi Vignesh,

    The thermal shutdown protects the IC once the junction temp exceeds 150deg. and the device will shut down. The junction temp. high above the abs max can damage the internals of the device. The recommended and absolute values have a difference  to ensure that the device will not shut down during the operation.  

    I would suggest using the recommended values given in the datasheet.

    Best regards,

    Tanvee

  • 0 in reply to Tanvee
    Prodigy 40 points

    Hi,

    Thank you very much for the response. This clears up our doubts.

    One another deviation, that we saw in the datasheet is that the electrical characteristics is provided for Tj=--40 to 125C. The typical value is defined for Tj=25C

    In that table Rds on high side typical is 120mohm. (Vin=3.6V)

    But in the graph below figure 5, the Rds value is approx 100moh, (Vin=3.6V). Which is the correct value. Same applies with Low Side also

    We are looking to get the values of Rds at min -40C, typ 25C & max 105C.

    Thanks

    Vignesh T

  • 0 in reply to Vignesh T
    TI__Genius 13440 points

    Hi Vignesh,

    In the table, the min value and max values are given for worse case operating conditions. the typical value is the normal behavior of device. I would suggest following the figure 5 that define rds value for different temperature.  Could you explain more about the application concern that helps to understand?

    Best regards,

    Tanvee