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TPS74801: Questions of TPS74801

Jimmy Lai
Expert 6845 points
Part Number: TPS74801

Dear Team,

The VDO requirements of the TPS74801 specification are shown in the figure below. According to the connection method in our schematic diagram, VIN=Vbias=3.3V, can it output a voltage of 2.5V? Our current application dropout is only 0.8V, please take a look, thank you!

Many Thanks,

Jimmy

  • 0
    TI__Expert 4385 points

    Hi Jimmy,

    TPS74801 is a NMOS LDO, which uses a Bias rail to achieve low Vin to Vout dropout. For best dropout performance, Vbias > Vin and Vbias - Vout > 3.25 V.

    In your schematic with Vin = Vbias = 3.3 V and Vout = 2.5 V, the Vin dropout voltage test conditions are not met for the 60 mV typical and 165 mV max dropout.

    For Iout = 1.5 A, typical Vin to Vout dropout is 1.31 V and max dropout is 1.6 V. TPS74801 will not support Vin = Vbias = 3.3 V and Vout = 2.5 V at Iout = 1.5 A.

    If your output maximum current is much lower, then the design may work. See Dropout Figures 6-8 in the datasheet for your application conditions, Vbias - Vout = 0.8 V and Vin - Vout = 0.8 V. Unfortunately, none of these curves cross the Vbias - Vout = 0.8 V point, even down to Iout = 50 mA. 

    TPS74801 is intended for Vbias > 4 V for Vout = 2.5 V. You may need to select a higher voltage for Vbias or choose a different LDO.

    Best,

    Eric

  • 0 in reply to Eric.Preiss
    TI__Expert 6845 points

    Hi Eric,

    Thanks for your great support.

    Do you have another solution for this spec to recommend?

    Many Thanks,

    Jimmy

  • 0 in reply to Jimmy Lai
    TI__Expert 4385 points

    Hi Jimmy,

    Could you provide the customer requirements?

    Output current capability, start-up or soft-start time, enable threshold voltage, acceptable input/output capacitors, transient requirements, PSRR, Noise?

    Best,

    Eric