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AD7323 output deviation with SPI frequency?

Question asked by ilhantaygurt on Jul 26, 2016
Latest reply on Sep 1, 2016 by ilhantaygurt

Currently we use AD7323 ADC with;

Vdd=12V,

Vss=gnd,

Vcc=3.3V,

Vref=3V

and moving average over 16 samples.

In case of 5Mhz SPI interface case we got the following results with straight binary coding;

InputOutput
00
10.99
21.99
33.0
44.0
55.0
65.92
76.74
87.57
98.41
109.26

 

As it is seen above 5V input case all results deviate from the input. If we decrease SPI frequency to 1MHz (our trial frequecny) all results turned back to normal.

 

Do you have any idea or feedback what could be the reason of this deviation?

 

Regards

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