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TPS7A4001: Output voltage variation based on input voltage variation

Nanjunda M
Expert 2485 points
Part Number: TPS7A4001

Hi,

I have a requirement where I would like to use the TPS7A4001DGNR to generate the variable voltage from 85V to 90V based on my input voltage which can vary from 88V to 92V.

Is it possible to do the above variations with TPS7A4001DGNR?

If I set the Output voltage to 88V with R1(88.8K) and R2(1.2K) values, then If I provide 88V input what would be the response of the Regulator?

Please let me know ASAP.

Thanks & Regards,

Nanjunda M

  • 0
    TI__Mastermind 43610 points

    Hi Nanjunda,

    As with any LDO, if VIN is at the VOUT target regulation voltage, the LDO will work as a load switch. Meaning, the LDO will do its best to regulate VOUT, but it will be in drop-out (VDO). So VOUT will be VIN-VDO. Worst case with a 50mA load, this would be 88-1.3 or 86.7V.

    I hope this helps.

  • 0 in reply to JCHK
    Expert 2485 points

    Hi JCHK,

    Thanks for the response.

    But here I have a requirement for output voltage following the input voltage.

    So is it possible to implement with this device, considering the dropout voltage. 

    The current consumption requirement is just 5mA for us.

    We would like to know what happens if the voltage keeps going low below the set output (say 88V in our case) and if we start decreasing the voltage from 90V to 80V what are the factors that can affect the output ? (performance etc.)

    Thanks & Regards,

    Nanjunda M

  • 0 in reply to Nanjunda M
    TI__Mastermind 43610 points

    Hi Nanjunda,

    if your load is just 5mA, then I would estimate your VDO being a worst-case of 130mV.  This is simply using the above VDO information from the datasheet 1.3V/50mA=26Ohm, 26Ohm*0.05=130mV.

    So here you would have 88-.13 or 87.87V at the output. 

    Is this OK for your application?

  • 0 in reply to JCHK
    Expert 2485 points

    Hi JCHK,

    Thanks for the calculations.

    In our application aiming to generate different outputs with same regulator with different input voltages.

    So as per your explanation, I think based on the input the output can be varied by maintaining the current constant.

    Thanks & Regards,

    Nanjunda M

  • 0 in reply to Nanjunda M
    TI__Mastermind 43610 points

    Hi Nanjunda,

    If I understand you correctly, yes, the TPS7A40 can work as a high-voltage current-limited switch.

    Regards,