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TPS65400: TPS65400 ISSUES

JAMES MARR97
Prodigy 50 points
Part Number: TPS65400

1)  Is there any way to get temperature out of the chip?

2) When we turn a ENABLE off it takes the chip 40-50uS to stop output switching, is there something we can do to speed this up?  INFO - we are making a power supply for an FPGA that needs sequencing which is done with a PIC uContoller.  We have 3 shutdown modes, a standard shutdown controlled by the PIC, a FAULT shutdown (all supplies shut down at the same time, are pulled to ground with FETs, using the chip CE line, in case of any supply overvoltage, this works great by the way, no CE delay to output), and a FAST sequenced shutdown, in case we loose battery.  This is controlled by the PIC by a fast de-sequencing using the ENABLE lines and we are shorting the output of the supply to ground with our pull down FETs for 40-50uS until the chip stops switching.

  • 0
    TI__Genius 9550 points

    Hi James,

    I am looking into this thread. And will give you feedback on Monday.

  • 0
    TI__Mastermind 19080 points

    Hi James,

    1. Are you asking how to measure the IC temperature with non-contact method? You may use a thermal camera to measure the case temperature, and then calculate the juction temp with thermal resistance.

    2. The switching should be stopped immediately when CE falls below the disable threshold. There should be no 40-50us delay. Please double check it. Thanks!

    Regards,

    Hao

  • 0 in reply to Sam(MPAA) Zhang
    Prodigy 50 points

    1)  Basically I want the know what the die temperature is so we can shut down the supply (chip) before the chip shuts itself down.       We need to do a sequenced shutdown.       We have temp sensors on both chips but that is not the die temp that will shut down at 160 degree C.

    2)  As I said the CE functions works fine and there is no delay but you cant do a sequenced shutdown using this pin.       We are using the ENx pins to do a controlled shutdown but there is a 40-50uS delay from the ENx pin input to the output to stop switching.  Please re-read my #2, it has all the info there!

    JMarr

  • 0 in reply to JAMES MARR97
    TI__Mastermind 19080 points

    Hi,

    1. To know the junction temperature, please refer to Chapter 7.4 in the datasheet. You may need to know the board temperature near the IC and also the power loss. Then junction temperature can be calculated. Power loss can be inferred by Vin/Vout and the efficiency curve.

    2. I did see the tens of microsecond disable delay on the EVM. For the application you described, I suggest you to,

        a. Turn off the device via I2C command. This can keep the power off sequence by a simple I2C written to the device. No need for split ENSWx control.

        b. Set the single enable in (D2h) PIN_CONFIG_00. Then you can use a single ENSW1 to power off the device with a sequence. 

    Regards,

    Hao

  • 0 in reply to JAMES MARR97
    TI__Mastermind 19080 points
    Also, all the 3 power off models you described are supported by the I2C commmand of the device. They are, normal power off with programmed sequence, immediately off(shut down at the same time), soft off(with internal discharge FET). Please refer to the register (01h) OPERATION.