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Part Number: UCD90120A
I have used reference design PMP9444 for Kintex Ultrascale. I set recommended values from Xilinx datasheet as the warning levels.
I am getting UV warnings for MGTAVCC. Please see attached picture.
FDPD is measuring MGTAVCC = 0.986V.
When I measure MGTAVCC with a multimeter (true RMS), I see exactly 1.0V.
What can influence precision of FDPD measurement ?
Should I set UV level lower by 14 mV ?
There are many things can contribute to these
1. Reference voltage inaccuracy due to V33A ripple
2. Noise on MON pin
3. Grounding noise
4. Voltage divider resistor accuracy
5. Incorrect scale ratio in configuration
6. High input impedance to MON pin.
7. Part-to-part variation.
The multimeter only measure the RMS value, there could be some fluctuation on the ADC input which does not captured by the multimeter.
Could you please have some scope for the questioned rails? please make sure that AC couple is used and adjust both vertical/time scale so that the fluctuation pattern is shown. ADC sampling is not synchronized with power stage’s switching frequency, therefore the sampling point may occur at any point within a switching period, as a result, the rail’s voltage ripple could be reflected on the ADC reading.
Also the ripple on V33A may affect reference voltage therefore affect ADC. Could you please check V33A ripple? If it has > 10mV ripple, try a RC filter to attenuate the ripple.
Did you have the decouple capacitor on the MON pin as recommended to filter some noise on the MON(ADC) pins?
As for the UV tolerence, you can refer to the POL data sheet to have it set properly.
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