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TLV713: Active pull-down engaging when Vout >> Vin, with EN tied to Vin

Jeffrey Wright
Expert 2855 points
Part Number: TLV713

Hello;

There seems to be indeterminant behavior when the TLV71333's output is pulled to another 3.3V rail, while its input slowly rises from ground, and EN is tied to Vin. During a transition from a buck switcher (which supplies the 713's input) from another 3.3V LDO, on some boards it appears that the 713's active pull-down gets enabled, when its input is below its minimum, even though EN is tied to Vin

I note from the datasheet the graph of the power up and down sequences, where the 713 doesn't begin operating until Vin is approx 1.3V.  I understand this scenario is out of bounds, but can you clarify what short of behavior to expect when its Vout is pulled to 3.3V, while its input is much lower? My assumption is that, once it begins to regulate, it will just turn of its pfet, but since its body diode will conduct, will that somehow enable the active pulldown??

Thanks 

  • 0
    TI__Genius 13085 points

    Hi Jeffrey,

    I think what you are describing is actually is the internal body diode you mentioned conducting current from Vout back to Vin since Vout is more than a diode drop higher than Vin. This is a very risky thing to do with an LDO unless the LDO datasheet specifically says it has reverse current protection. 

    TLV713 (like most LDOs) does not have reverse current protection and so the LDO can be damaged if too much current is flowing through the LDO (this is mentioned in the datasheet, I've added a quick snippet for reference). 

    Here is some more info from our Preventing Reverse Current blog post about how to protect an LDO from being damaged due to reverse current. The Load Switch product line also has a blog post on how to use a load switch to protect systems from reverse current.