• Resolved

TPS715: about reverse voltage condition

Part Number: TPS715

Hi,

Could you tell me about TPS715 protection and additional circuits?
My customer is considering TPS715.
During the evaluation,The output voltage appeared to the input side in Vin=open condition.

I expected the parasitic diode of the internal FET to be on.
Is my understanding correct?
And could you tell me the reverse voltage and current protection circuit example.

Customer condition is:
Vin=19.5,Vout=3.3V,Iout=10mA

Best Regards,
Yusuke/Japan Disty

  • Hi Yusuke,

    You are correct that in a reverse current situation (Vout exceeds Vin), the parasitic diode of the internal FET for TPS715 will turn on to provide a path for the current. Please note that current in the direction from OUT to IN is not limited; therefore, if extended reverse current is expected, external circuitry should be added.

    Commonly a Schottky diode is placed in parallel with the internal parasitic diode to provide a robust path for the reverse current.

    Very Respectfully,
    Ryan
  • In reply to Ryan Eslinger:

    Ryan-san,

    Thank you for your response.
    I understood what you explained.
    Let me ask you one more thing.

    Input voltage appears to the output when the turned on.
    Please tell me the cause and the countermeasure method.



    Best Regards,
    Yusuke/Japan Disty

  • In reply to Tsukui Yusuke:

    Hi Yusuke-san,

    During device startup, the device will be in dropout because VIN will be less than VOUT(nominal). When the device is in dropout, the transient response capability from a VIN line transient is reduced. In this case, when there is a high voltage slew rate (dV/dT) on the input, that slew rate can couple into the output. This is why the output (VOUT) steps up when VIN steps up.

    For this device, the only option is to reduce the slew rate on the input, or clamp the output voltage with a zener diode. A resistor in series with the LDO can help reduce the slew rate.

    Regards,
    Mike