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Original question:

TLV767: Does Cout 47uF need a schottky diode to prevent reverse current?

TLV767: Reverse protection diode required?

Leon Hermans
Prodigy 130 points
Part Number: TLV767

Tool/software:

Hello -

In our application we have a 12V input to the TLV76701DRVR with output set at 5V.  The output capacitor is 4.7uF.  The load is minimal (<<1mA).

On the input side we have ~ 13.3uF of combined capacitance with a load of 1400ohms.  In the event that the 12V supply disappears due to mains power loss, we would expect this voltage to decay below Vout.  We don't expect Vin to ever suffer a direct short however.  

Is the TLV767 able to support a reverse current on the order of 5mA? or do you recommend installing the reverse Schottky diode? 

Thank you

Leon

  • +1
    TI__Guru 50025 points

    Hi Leon,

    The issue is that if the input disappears quickly, it's not just the 1400Ω that will result in reverse current; the voltage differential from OUT to IN, if large, can result in a reverse current that is much larger than 5mA. In general, the normal guidance is to limit reverse current to 5% of the rated current (50mA for this device), but in this scenario the reverse current is not limited. So, either the reverse diode from OUT to IN would be required to protect the device, or a diode at the input (before the input cap) would also prevent the LDO input from collapsing along with the main supply. 

    Regards,

    Nick