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MSPM0G3507: OPA non-inverting input with DAC bias in OPA0

Andy Fan
Prodigy 100 points
Part Number: MSPM0G3507
Other Parts Discussed in Thread: SYSCONFIG

Hello, my OPA settings as blew:

use OPA0, bias and gain for signal.

this is my SysConfig 

Here is the PinMux 

Questions:

1.The bias is not effective, whatever the DAC output. The same with the <MSEL> use the <GND>

2.But the gain for signal is OK.

3.For PINMUX , why the pin select is PA26/30.    All pins some like a pair.  what means "/30"?

  • 0
    TI__Mastermind 24405 points

    Hi Andy,

    Andy Fan said:
    1.The bias is not effective, whatever the DAC output. The same with the <MSEL> use the <GND>

    How does you configure DAC output? You should enable DAC12 peripheral for this input.

    Andy Fan said:
    3.For PINMUX , why the pin select is PA26/30.    All pins some like a pair.  what means "/30"?

    It means the pin number, if you check the PIN number of the PA26, it should be 30.

    B.R.

    Sal

  • 0 in reply to Sal Ye
    Prodigy 100 points

    1.DAC output is enabled. 

    I can change the output value to change the voltage. And the signal of PA15 is OK .

  • 0 in reply to Andy Fan
    TI__Mastermind 24405 points

    Hi Andy,

    What is the input voltage of IN0+? Is it possible that the output voltage is out of range?

    I will also do some test according your description and then update here.

    B.R.

    Sal

  • 0 in reply to Andy Fan
    TI__Expert 8485 points

    Hi Andy,

    I wanna know if this problem of opa usage have been solved? 

    And I have done some test of opa, and the gain and DAC output work normally. 

    Here is some comment of your issue:

    1. DAC output results could be measured by PA15;

    2. The output voltage is ((V_IN - V_DAC)*GAIN + V_DAC), and make sure the voltage is less than VDD.

    And if you have solved the problem already, please tell me and I'll close this thread. Thanks!

    Best Regards,

    Pengfei

  • +1 in reply to Pengfei Xie
    Prodigy 100 points

    OK , I change the signal input to inverting pin ,and non-inverting pin fixed to VCC/2 .  because the DAC has be used to other function.

    So, maybe this discuss can be closed, Thanks a lot.