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MSP430FR5847: Common-mode input range about Comparator

O.H
Mastermind 6980 points

Part Number: MSP430FR5847

Hi experts,

As described below, the common-mode input range (VIC) of Comparator_E is set to "VSS~VCC-1".
Could you tell me what happens if a voltage exceeding VCC-1 is input?
If the value exceeds the MAX value but is less than VCC, is it correct to assume that it will not break, and will behave as if it is the MAX value? For example, if VCC=3.3V, the negative terminal is fixed at 0V, and the positive terminal is set to 2.4V or higher, will the comparator treat it as if + terminal = 2.3V is input?
image.png

Best regards,
O.H

  • 0
    Guru 25815 points

    For your example of input voltages of 0V and 2.4V, the common mode voltage is 1.2V.

  • 0 in reply to David Schultz
    Mastermind 6980 points

    Hi David Schultz,

    Thank you for your reply.

    David Schultz said:
    For your example of input voltages of 0V and 2.4V, the common mode voltage is 1.2V.

    Could you please tell me the formula used to calculate 1.2V?

    O.H said:
    Could you tell me what happens if a voltage exceeding VCC-1 is input?

    Do you have an answer to the above question?
    I'd like to know how the comparator behaves when a voltage of VCC-1 or higher is applied to its + input pin.

    Best regards,
    O.H

  • 0 in reply to O.H
    Guru 25815 points
    O.H said:
    Could you please tell me the formula used to calculate 1.2V?

    Common mode is a widely known concept. There is even a page at Wikipedia so I am not going to do that again.

    Exceeding the common mode input range will lead it undefined results. So don't do it.

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