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TLV700: Can I apply 5.5V on the OUT pin?

Sakeenah Khan
Expert 3355 points
Part Number: TLV700

Tool/software:

Hello,

I want to be able to disable the TLV70033 output using the switch S1 as shown below, so that a user can connect an external voltage up to 5.5V instead of the regulated 3.3V. Would it be ok to apply 5.5V on the OUT pin like this? The recommended operating conditions for VOUT is 4.8V max, but the abs max is 6V so I think it would be fine. Thanks!

Best, 

Sakeenah Khan

  • 0
    TI__Expert 4660 points

    Hi Sakeenah,

    While the part is disabled using the switch, what will be the Input voltage (VBUS)?

    If Vout (i.e 5.5V) > Vin, reverse current flow might happen. As described in Section 7.3.1 of the datasheet, there is a built in body diode for protection, but this current is not limited. So as noted in datasheet, "if extended reverse voltage operation is anticipated, external limiting to 5% of the rated output current is recommended."

    Other than this, since your voltage will be less than the abs max rating of the pin, it should not damage the device.

    Best Regards,

    Bobby

  • 0 in reply to Bobby
    TI__Expert 3355 points

    Hi Bobby,

    Thanks for your reply. In this case VBUS comes from USB power and it is 5V, which is less than VOUT=5.5V. Does that seem ok? 

    Best,

    Sakeenah

  • +1 in reply to Sakeenah Khan
    TI__Expert 4660 points

    Hi Sakeenah,

    In this case Vout>Vin, and reverse current will flow.

    Ideally, reverse current should not exceed 105% of Iout max (210mA in this case). Continuous reverse current, or overcurrent conditions could degrade device performance overtime. If this condition is brief, it may not impact performance. 

    If you need design recommendations regarding reverse current, please see this app note: LDO Basics: Preventing Reverse Current

    Regards,

    Bobby

  • 0 in reply to Bobby
    TI__Expert 3355 points

    Hi Bobby,

    Thanks for sharing the app note! I added D5 to prevent reverse current as shown below. Hopefully that looks right! 

    Best,

    Sakeenah

  • +1 in reply to Sakeenah Khan
    TI__Expert 4660 points

    Hi Sakeenah,

    This should be good. 

    Just letting you know, this diode will act as a resistor in the normal operation of LDO, and will cause a voltage drop across it. Your Vin=5V is much greater than the minimum input voltage (Vout+0.3V) required, so I don't see the LDO operation getting affected. But keep this in mind in case your Vin is reduced for any reason.

    Also, it is recommended to ground the NC pin to improve the thermal dissipation of this LDO but this is not a requirement.

    Regards,

    Bobby