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TPS7A85: Shottky Diode for reverse current protection

Omer Kvitel
Prodigy 140 points
Part Number: TPS7A85

Hi

I would like to understand how to choose the shottky diode for reverse current protection:

From the data sheet, there is a recommendation to use a shottky diode for reverse current protection:

(Figure 57)

http://www.ti.com/tool/TPS7A85EVM-754?keyMatch=TPS7A85%20&tisearch=Search-EN-everything&usecase=part-number

 

I would like to know if there is a recommendation by TI to such a diode (what they used in order to verify it).

In the EVB: http://www.ti.com/lit/ug/sbvu029/sbvu029.pdf I didn’t find this implementation.

 

Regards

Omer

  • 0
    TI__Mastermind 43630 points

    Hi Omer,

    I would recommend picking a diode that can handle the worst-case peak current based on how much output capacitance you have at VOUT.  The worst-case scenario for reverse current is when the regulator is actively regulating and the input voltage is suddenly shorted. 

    I hope this helps.

  • 0 in reply to JCHK
    Prodigy 140 points

    Dear John

    Meaning if I plan for a 4[A] maximum current from the LDO - the diode needs to have this limit as well?

    Regards

    Omer

  • 0 in reply to Omer Kvitel
    TI__Mastermind 43630 points

    Hi Omer,

    No. The diode is only providing a path to discharge VOUT to VIN in the event that VIN is suddently shorted. Assuming you have a 47uF capacitor at COUT and VOUT is 3.3V, then the amount of energy stored on the capacitor is 1/2CV^2. or 255mW. if the load was drawing essential no power and VIN is shorted, this is the amount of energy that would be dissipated by the diode. In this case something like this could be sufficient.

    I hope this helps to clarify.