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TPS7A85: VBIAS supply threshold

sangeetha s1
Prodigy 110 points
Part Number: TPS7A85

Hi Team,

We are using the TPS7A8500 LDO in our application.Find the following requirements,

1. Vin : 2.2V & Vout: 1.9V , Iout : 2.6A

2.Vin : 1.4V & Vout: 1.1V,Iout : 3.7A

We dont have 5V supply in our board,Shall we give 3.3V for Vbias supply,If we provide 3.3V how much noise/ripple characterstics and AC/DC performance will be affteced for the output?

Kindly confirm the same for design clearance.

  • 0
    TI__Mastermind 44220 points

    Hi Sangeetha,

    The TPS7A85 has an internal charge pump (CP) that attempts to double VIN (Internally it is clamped as not to exceed the absolute maximum rating of the device). So for your cases above:

    1, With VIN=2.2V, the internal CP would be providing 4.4V for the gate Bias. In this case, the external 3.3V has no impact.

    2. With VIN=1.4V, the internal CP would be providing 2.8V. So in this case, the external 3.3V on VBIAS would improve the headroom which will help with PSRR.

    I hope this clarifies the issue for you.

  • 0 in reply to JCHK
    Prodigy 110 points

    Hi John,

    Thank you for reply,