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MSP430FR5964: The voltage that can be supplied to the VeREF+ pin.

O.H
Genius 5340 points
Part Number: MSP430FR5964
Other Parts Discussed in Thread: MSPWARE

Hi experts,

Please tell us about "Table 5-29. 12-Bit ADC, External Reference" in the datasheet.

Q1: When using VeREF+, is it OK to supply a voltage below 1.2V? (Specifically, 0V is supplied.)

We would like to use an external power supply for the ADC reference voltage.
While the ADC is in use, it provides 3.3V to the VeREF+.
However, I would like to stop supplying 3.3V and supply 0V while not using the ADC.

The content of "Table 5-29. 12-Bit ADC, External Reference" does not mean that a voltage below 1.2 should not be added, but can be interpreted as requiring at least 1.2V when using the ADC.
MSP430FR599x, MSP430FR596x Mixed-Signal Microcontrollers datasheet

Q2:Is it necessary to set the GPIO pin before supplying 0V as a workaround when 0V cannot be used for VeREF+?
Or, if you have any other workarounds, please let me know.

Best Regards,
O.H

  • 0
    TI__Expert 7015 points

    Hi, O.H, 

    O.H said:
    Q1: When using VeREF+, is it OK to supply a voltage below 1.2V? (Specifically, 0V is supplied.)

    VeREF+ is input pin. So generally it is no problem to to supply it below 1.2v. The minimum 1.2v in the table 5-29 is for ADC12 working condition. If ADC12 is not in use, I think it is ok to allow input voltage less than 1.2v. But to protect the analog input pin, it is better to switch this pin to GPIO functionality by setting P1SELx when VeREF+/- is not used. 

    O.H said:
    Q2:Is it necessary to set the GPIO pin before supplying 0V as a workaround when 0V cannot be used for VeREF+?
    Or, if you have any other workarounds, please let me know.

    Sure. You can do this as I mentioned above, and it will be better than supplying 0v to VeREF+ directly. Note, please set it to GPIO input functionality before supplying 0v to this pin. 

    Thanks, 

    Lixin 

  • 0 in reply to Lixin Chen1
    Genius 5340 points

    Hi Lixin

    Lixin Chen1 said:

    VeREF+ is input pin. So generally it is no problem to to supply it below 1.2v. The minimum 1.2v in the table 5-29 is for ADC12 working condition. If ADC12 is not in use, I think it is ok to allow input voltage less than 1.2v. But to protect the analog input pin, it is better to switch this pin to GPIO functionality by setting P1SELx when VeREF+/- is not used. 

    Thanks for the reply.
    I understood that there was no problem and that it was better to switch to GPIO.

    I confirmed the sample code, but in the content of "MSP430FR599x_MSP430FR596x_Code_Examples" included in MSPware(3_80_09_03), only BIT0 was set for P1SELx even though P1.1 was treated as VeREF+.

    However, in the content of "MSP430FR599x_MSP430FR596x_Code_Examples" downloaded from the product page (www.tij.co.jp/.../MSP430FR5964), P1SELx was set to BIT0 and BIT1.

    I feel like the content of MSPWare hasn't been updated, so I'll share it with you.

    Best Regards,
    O.H

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