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ADC invert signal sample-and-hold of MSP430F5438A

milanqingren
Prodigy 235 points
Other Parts Discussed in Thread: MSP430F5438A

Hi,

 

From the family user's guide of MSP430F5438A, the polarity of the SHI signal source can be inverted with the ADC12ISSH bit, which is in ADC12_A Control Register 1 (ADC12CTL1).

 

However, there isn't too much information about this signal inverting function of ADC in user's guide.

 

From my understanding, if there is a negative 1.5V input voltage to ADC, this negative voltage can be inverted to +1.5V by setting the ADC12ISSH bit to 1.

 

Is my understanding correct, or I missed something?

 

Thanks

 

Liu

  • 0
    Expert 1170 points

    Hi,

    no, the ADC12ISSH does not invert the input signal. Take a look in the MSP430x5xx Family User's Guide:

    http://focus.ti.com/lit/ug/slau208g/slau208g.pdf

    On page 467 you find the block diagram of the ADC12 module. Here you also find the ISSH bit (that's the same as ADC12ISSH). Here you see, the this bit allows you to invert the trigger signal for the sampling timer or the SAMPCON signal. SAMPCON signal is the signal that defines when sampling is done (sample capacitor is charged) and when the A/D conversion is done.

    In the device specific datasheet you find the information that the ADC12 input signal should be within the range 0V to AVcc.

    Regards.

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