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TPS7A85: 0.8V output setting

Part Number: TPS7A85
Other Parts Discussed in Thread: TPS7A84

How should we set FB circuit when we want to set output voltage 0.8V?

Is it OK that OUT line is connected to FB pin directly? Or should we connect OUT line to SNS pin and put Cff between SNS pin and FB pin?

Best Regards,
Kohei Sasaki

  • Hi Sasaki-san,

    For 0.8VOUT, this is the recommended schematic:

    Does this answer your question?

    Regards,

  • Hi

    Please let me ask additional question.

    We use TPS7A8500 with 0.8V output typically, however there is the case which we adjust output voltage slightly as 0.8xV.
    In this case, can we use the following schematic? We will add the bottom FB resistor when we want to adjust output voltage.

    Best Regards,
    Kohei Sasaki

  • HI Sasaki-san,

    The problem you would have with the above approach is that the Temperature coefficient of the TPS7A84's internal 12.1K resistor is not the same as the external resistor (which is this case you would want it to be much larger to only slightly raise VOUT. Note the 50mV pin has a pull-down resistor of 193.6K.

    Another approach might be to simply tie the 800mV pin to SNS. This changes the pin weights as shown below:

    While we have never tested the below, It seems logical if you tie both the 1.6V and 800mV to SNS you would get the following:

    These pins only add to the reference if grounded so you can either do that with 0ohm resistors, and MCU or a GPIO expander as described in this application note: 

    I hope this helps.

    Regards,