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Original question:

LMR36506: Calculation on Enable voltage and resistor values.

LMR36506: LMR36506

Adarsh Raju
Prodigy 60 points
Part Number: LMR36506

Can anyone please explain the working of the PGOOD signal?

From the datasheet, I understood that it will disable the Output if the value goes up or below the particular range. Correct me if I'm wrong. 

How does the Pgood signal select the range of value?

  • 0
    TI__Genius 12475 points

    Hi Adarsh, 

    Thank you for your question. PGOOD will not disable the device if the value goes up or below a certain range. Instead PGOOD is an output signal that can be used to tell another device when the LMR36506 is operating within regulation or not. You can find these thresholds of regulation on page 7 of the datasheet under the power good section of the EC table. 

    Thank you,

    Joshua Austria

  • 0 in reply to Joshua Austria
    Prodigy 60 points

    Hi Joshua, 

    If I'm pulling up the PGood signal to output and let it be a variable output configuration. How does PGood signal work then on the regulation?

    Thanks 

    Adarsh 

  • 0 in reply to Adarsh Raju
    TI__Genius 12475 points

    Hi Adarsh, 

    PGOOD will have no effect on the regulation, it is only for outputting the state of the device (whether it's output is in regulation or not). If you want to change the device's regulation, you can use the enable pin to enable or disable the device based on the thresholds on page 6 of the datasheet. 

    Thank you,

    Joshua Austria

  • 0 in reply to Joshua Austria
    Prodigy 60 points

    Joshua, 

    How can I use Pgood signal for the undervoltage and overvoltage protection at the output of the regulator? 

    Let's say my output voltage is 3.3V and can I utilise Pgood signal for the output OV/UV protection?

    Best Regards 

    Adarsh Raju 

  • 0 in reply to Adarsh Raju
    TI__Genius 12475 points

    Hi Adarsh, 

    Thank you for your question. You can use PGOOD to output a signal that can be used by a second device. If the output of the device falls below a certain level or goes above a certain level, PGOOD will change its output and can trigger a reset. These levels are outlined on page 7 of the datsheet.

    For example, if your regulator is powering an MCU, and you want to make sure the MCU is protected at its power input, you can use the PGOOD signal and connect this to the MCU. Then you can have the MCU turn off/reset when it receives a PGOOD signal that signifies some undesirable characteristic (power too high or power too low). 

    While PGOOD is usable for other devices, the PGOOD signal is an output only signal for the LMR36506 and cannot be used to reset the buck itself. The EN pin on the other hand can turn the buck on and off.

    Please let me know if you have any other questions,

    Joshua Austria