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TPS7A52: 0.8V not generating from TPS7A52 using below resistors for R1 and R2

sairam kishore
Prodigy 30 points
Part Number: TPS7A52
Other Parts Discussed in Thread: TPS7A92, TPS7A57, TPS74401

Hi Team,

i have used TPS7A52 in our design to generate 0.8v which it supports. There was no R1 and R2 values defined for 0.8v in the datasheet.

in order to get 0.808 volts, I calculated the resistor values to be 100ohm as R1 and 100k as R2. With this configuration, i dont see any voltage at the outpit.

Could you share me proper resistor to use for R1 and R2 in getting a voltage very close to 0.8V

Regards,

Kishore.

  • 0
    TI__Mastermind 34055 points

    Hi Kishore,

    Those resistor values will give you 0.8008V.  If you want 0.808V, you should change the 100 ohms to be 1k ohms instead.

    Regardless you should still see voltage on the output.  Check to make sure that you have at least 1.1V on the input pin and the enable pin, and 3V on the bias pin.

    Thanks,

    Stephen

  • 0 in reply to Stephen Ziel
    Prodigy 30 points

    Hi Stephen,

    I checked in the meanwhile that I missed to provide 3V bias for our input source of 1.2V.

    We thought that it wouldn't be recommended to use 2.5V input to generate 0.8V/2A load due to huge dropout voltage and power dissipation and used 1.2V but missed this external bias voltage requirement of 3V.

    But as we don't have bias voltage availability from 3 to 6.5V on board, do you recommend using 2.5V to generate 0.8V/2A still if not we need to identify alternate options.

    Regards,

    Kishore.

  • 0 in reply to sairam kishore
    TI__Mastermind 34055 points

    Hi Kishore,

    The BIAS pin must have 2.9V (or more) to be above the UVLO voltage (with a typical voltage required of 2.83V), thus 2.5V will not be enough in most cases.

    It sounds like you have 2.5V and 1.2V in your system, and you need to generate 0.808V with 2A loading.  Your best options are the TPS7A57 or TPS74401.  If you change the 1.2V to be 1.4V, you can also look at the TPS7A92.

    Thanks,

    Stephen

  • 0 in reply to Stephen Ziel
    Prodigy 30 points

    Hi Stephen,

    Yes you are correct we have only 1.2V and 2.5V on board and other 12V which cannot be used as bias matching to our requirement.

    Thanks for sharing the other options that we could explore to generate 0.8V  from the 1.2V available. Will use them for our design. 

    We are good with the details received and can close this ticket.

    Thanks & Regards,

    Kishore.