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Newbie 400garrison
Newbie
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Registered: ‎04-11-2017

Example of measuring negative voltage rail on XADC

Is there an example of how one can measure a negative voltage rail using the Xilinx System Monitor (XADC)?  I see on pg 80 of UG480 that negative input voltages clip to zero code.  I just want to measure my negative voltage rails on the XADC if possible.

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Registered: ‎01-22-2015

Re: Example of measuring negative voltage rail on XADC

@400garrison

As shown on about page 27 of UG480, the analog external input channels of the XADC can be configured as bipolar. Then, the XADC can measure negative voltages down to -500mV (see Figure 2-3).  

If you have a negative voltage(rail) below -500mV, simply pass it through a two-resistor voltage divider that creates a voltage in the 0 to -500mV range - and feed this scaled-down in-range negative voltage to the XADC.

Mark

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