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Original question:

TPS25750: Abnormal 18W Source with TPS25750EVM

TPS25750: TPS25750EVM 9V problem

Michael Koelbl
Intellectual 290 points

Part Number: TPS25750
Other Parts Discussed in Thread: TPS55288, , , TPS51225

Hello,

on our TPS25750EVM we see the 9V problem as described in the thread "TPS25750: Abnormal 18W Source with TPS25750EVM", too. Are there any new findings on that problem? We want to use the TPS55288 buck-boost converter as adjustable source and are afraid that we get the same problem.

By the way we had the same problem with 15V but only some times. With 20V we never have seen the problem. 

Have you recognized that both PP5V and PPHV are connected to VBUS at the same time when the error occurs? One can see the increasing voltage (from 5V to higher voltage) on P5V which seems to switch off the TPS51225 3.3V supply.

  • 0
    TI__Mastermind 30000 points

    Hello Michael,

    There is no new findings for this fail case and is a known failure. This is not the final version of the EVM. The final version of the EVM will not use a DCDC, but instead a battery charger that the TPS25750 controls via I2C. Since we are changing the architecture of the TPS25750EVM, and will not longer have the problem you described, we have not invested resources into determining the failure you highlight. 

  • 0 in reply to Adam Mc Gaffin
    Intellectual 290 points

    Hello Adam,

    that means the TPS25750 cannot be used for high voltage power source! As a workaround you're changing the Evalboard to 5V source and high voltage sink but what shall customers do who want a high voltage power source? We'll always will have a kind of slew rate on the changing voltages. We need an information how the voltage transitions have to be.

    Or can we do another way: As mentioned we want to use TPS55288 as buck-boost converter and of course it also delivers 5V. So in my opinion we do not need the PP5V to VBUS switch at all as I can supply 5V also at PPHV. At PP5V I would connect a low current 5V supply (for CC pins, VCON). With this solution we would be more than glad. Is this possible?

    Michael

  • 0 in reply to Michael Koelbl
    TI__Mastermind 30000 points

    Michael Koelbl said:
    that means the TPS25750 cannot be used for high voltage power source! As a workaround you're changing the Evalboard to 5V source and high voltage sink but what shall customers do who want a high voltage power source? We'll always will have a kind of slew rate on the changing voltages. We need an information how the voltage transitions have to be.

    This is not correct. The TPS25750 is capable of sourcing high voltage contracts, as you were able to verify with the 20V source contract. What I am saying is that in the final version of this EVM, it will use a battery charger instead of a DCDC. The EVM will still offer 20V source, 20V sink capabilities as the TPS25750 is capable of acting as both a high voltage source and sink. 

    Michael Koelbl said:
    s mentioned we want to use TPS55288 as buck-boost converter and of course it also delivers 5V. So in my opinion we do not need the PP5V to VBUS switch at all as I can supply 5V also at PPHV. At PP5V I would connect a low current 5V supply (for CC pins, VCON). With this solution we would be more than glad. Is this possible?

    No since the TPS25750 always uses the PP5V to VBUS power path for a 5V contract.