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TPS7A80: Reverse voltage between IN and OUT

Part Number: TPS7A80
Other Parts Discussed in Thread: TPS7A94

Hello team,

TPS7A80 datasheet abs max table says OUT abs voltage rating is 7V(max) independent from Vin voltage. However, datasheet 7.3.1 says reverse voltage measure needs to be done externally.

I would like to know profile what level of reverse voltage and its period of time requires external measure.

Could you let me know guideline what reverse voltage and its time can be fine for TPS7A80 without needing external circuit? Like, in case reverse voltage is 0.8V/0.5V/0.3V, TPS7A80 will be safe for xx msec/ yy msec/ zz msec.

The background of this inquiry is that reverse voltage will happen when input voltage is shutoff  and output voltage remains by output capacitor. and I would like to make the solution as small as possible so I don't want to add schottky diode unnecessarily.

Or, TPS7A94 output discharge function will protect from such reverse voltage condition caused by immediate input voltage shut off even though its abs max voltage of OUT is Vin + 0.3V?

Best regards,

  • Hi Sato-san,

    All of our LDOs without the reverse current protection feature should limit Vout<=Vin+0.3V in order to keep the parasitic body diode from starting to conduct. Our LDOs can survive some reverse current but it needs to be kept less than 5% of the nominal current (so 50mA for TPS7A80) and will likely happen at 400mV or more differential between Vout and Vin. 

    The Active discharge feature can help with this, however the active discharge circuit needs Vin>UVLO to ensure it operates properly (such as when the device is disabled) so if Vin falls quickly this may not discharge Cout enough. If you know the approximate ramp rate of the Vin when it falls then you could size the load (add some resistance to GND) to discharge Cout quickly enough, this could help eliminate the need of a protection diode but would reduce the power efficiency of the total solution.