AnsweredAssumed Answered

AD5522 Measure current reduced range.

Question asked by Trygve on Dec 9, 2014
Latest reply on Dec 10, 2014 by Trygve

On the ( custom-made ) board I'm debugging, the PMU ( AD5522 ) is powered with:

AVDD =  +10V
AVSS =  -5V
VREF =  +2.5V
I know this AVDD/AVSS combination violates the PMU DataSheet.

Further I'm using:

OFFSET-DAC = 0x0000
Current Gain = 5
Measout Gain = 0.2

In the FVMI mode, I get the expected/desired behaviour in the lower and mid parts  of the nominal current ranges.
However, for both internal and external sense-resistors, with consistency the voltage at MEASOUTx
stops increasing when the DUT-current reaches approximately 77% of the nominal maximum value.
At this point Vsense = Rsense x Idut = 0.70V, this is illustrated in the table below ( The table actually shows the true Idut at onset of the "MEASOUT clipping").

 

Onset_Clipping.jpg

 

 

The plot below shows the results from a series taken with an external Rsense = 50 ohm.

 

Currents.jpg

 

 

 

 

Can anyone advice me a better PMU setting/configuration that could give me current measure capability
also in the higher part of the nominal range ? ( Given the erroneous AVDD/AVSS combination I'm already aware of).

 

Thanks

Trygve

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