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TPS544C25: Power Good low

LALIT VERMA
Expert 1695 points
Part Number: TPS544C25
Other Parts Discussed in Thread: TPS546C23, TPS543C20A, TPS543B20

Hi,

We have used TPS544C25 in our project for generating 1.2v @ 11A and 1.2v @ 7A.

We are getting 1.2v from both the regulators but power good signal from both the regulators are low.

And when we read the STATUS_VOUT register, we got 0x40h from both the regulators which means OVW fault is triggered.

We will not be using PMBUS, so please advise how to prevent OVW fault to trigger and power good to go low.

Also, as can be seen from the schematics, we have connected a transistor to TSNS pin, but as per datasheet this pin is set for soft start detection by default(and we haven't change the default condition using PMBUS) and for that a resistor should be connected to TSNS pin.

But still we are getting around 5ms rise time for the output.

So, my question is can we keep the schematic as same with transistor connected to TSNS pin and TSNS pin set for soft start detection by default, and still have the soft start circuitry works fine?

An early response will be highly appreciated.

Thanks,

Lalit

  • 0
    Expert 1695 points

    Hi TI Team, 

    Can you please update on this?

    Thanks,

    Lalit

  • 0
    TI__Guru 56985 points

     

    1) Over Voltage Warning (OVW) is triggered when the voltage sensed at the VOUTS+ minute VOUTS- pins exceeds the voltage programmed into the VOUT_OV_WARN_LIMIT.  With an external divider from DIFFO to FB and VOUT_SCALE_LOOP not updated to match, that is expected. 

    The TPS544C25 is not intended to operate with a mismatch between the internally programmed VOUT_SCALE_LOOP and the external divider.

    For alternatives:

    If you will use PMBus for status and telemetry, the TPS546C23 offerings similar PMBus features to the TPS544C25, but it intended to be used with an external divider which does not need to match the internal VOUT_SCALE_LOOP function.

    If you will not use PMBus, you can consider the TPS543B20 or TPS543C20A converters for you 1.2V supplies.

    2) The SS programming function of the TPS544C25 forces a 10μA current on the pin-detection pin and measures the voltage.  Using of a transistor is not recommended can could result in TSS programming to the value selected by adjacent resistor values. (the design is likely detecting the transistor as 34.8kOhms due to approximately 350mV on the transistor at 10μA.  Due to tolerance of the current source and transistor, that could be decoded as 3ms or 7ms on any given power-up.  If the design is tolerant to changes in the soft-start, that may be acceptable.