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MSPM0G1506: Can PA21 be used as analog input (A1_7) when internal VREF is being used?

AnBer
Mastermind 30170 points
Part Number: MSPM0G1506
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Team,
In case customer needs all possible pins for IOs and at the same time needs internal VREF (no need to use external CAP on VREF+, VSS/VREF-, no need of external REF).

-Can PA21 be used as analog input (like A1_7) when only internal VREF is being used?
-Can the IOMUX be configured in a specific way to enable this?

Looking at SYSCONFIG it does not seem to be possible to enable VREF and GPIO/PA21.
It shows a conflict.

-Is there a workaround possible to enable both internal VREF and PA21 as GPIO?

Thanks in advance,

Anthony

  • 0
    TI__Genius 10611 points

    Hi Anthony,

    Once you enable internal Vref, the PA21 should only be served as the Vref-. So the GPIO or A1_7 function can not be used.

    Regards,

    Zoey

  • 0 in reply to Zoey Wei
    TI__Mastermind 30170 points

    Hi Zoey, Thanks for your quick answer.

    I would like to get a better understanding were the limitation lies.
    At the IOMUX level I assume that a config happens to select between both input src (VREF and GPI A1_7).

    -Can't the Input mux setting be overwritten after VREF is enabled?
    -Is it technically possible to overwrite but has not been validated (ie so unknown behavior)? Or is it not all all possible?

    Thanks in advance,

    Anthony

  • 0 in reply to AnBer
    TI__Genius 10611 points

    Hi Anthony,

    Once you use the internal reference, the internal negative reference can be connected to the PA21 directly. So if you trying to use it as the normal GPIO, for example output high, the Vcc will short directly to the GND.

    Zoey

  • 0 in reply to Zoey Wei
    TI__Mastermind 30170 points

    Hi Zoey,
    Thanks for the confirmation!
    Customer can do without PA21 at the end.
    A follow up question still about the internal VREF:

    To limit the number of components, we would like to pass the internal VREF to outside circuitries (as a reference for the external OPAMPS, but the current capability is not sufficient for our application).
    -Can we tie the VREF to internal OPAMP eg, OPA0_OUT, and use it as a reference output (with output load current of 9 or 30mA – depending on the GBW setup)?
    -Or is there a better way to buffer the internal VREF?

    Thanks in advance,

    Anthony

  • 0 in reply to AnBer
    TI__Genius 10611 points

    Hi Anthony,

    I think use internal OPA as voltage follower is a good idea. Or you can use DAC + OPA to serve the external reference for other device.

    Regards,

    Zoey