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TPS62136: PowerGood behaviour during Tracking

Bernhard Boehmer
Expert 1110 points
Part Number: TPS62136

Hello TI,

Since FB internally tracks the TR pin, please could you confirm the working of the PG pin in a tracking scenario? The PG rising threshold is typically 96% - is this of the final FB value (0.7V, when TR >= 0.7V) or is this of the instantanious tracked FB value (TR pin) which could be lower than 0.7V?


Stated differently, is there a possibility of a PowerGood during tracking when TR is less than 0.7V, or can PowerGood only occur once TR reaches 0.7V?

And therefore, once a tracked supply is stable and PG released high, will PG be pulled low if TR subsequently decreases below 0.7V?

  • 0
    TI__Guru**** 150770 points
    Hi Bernhard,

    Yes, PG is based on the 0.7V level on FB not on the SS/TR voltage. This can be understood under a normal startup scenario, without driving SS/TR. SS/TR will ramp up and Vout with it. When Vout gets to the right level, PG goes high. SS/TR will also be at the same voltage, as there is a 1:1 gain between SS/TR and FB.

    If SS/TR is actively driven down, PG will go low when Vout drops sufficiently. Note that PG is based on Vout, not on SS/TR so if the load is light in PFM mode, Vout will stay higher above SS/TR as described in the D/S:
    For decreasing SS/TR pin voltage in PFM mode, the device does not sink current from the output. The resulting decrease of the output voltage may therefore be slower than the SS/TR pin voltage if the load is light.