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AD7766 Is giving only 12 correct bits.Remaining 12 bits are noise.

Question asked by husain on Feb 25, 2017
Latest reply on Apr 16, 2017 by jcolao

Hello,

I am using the AD7766 ADC for designing a circuit.I have used a single ended to differential driver at its source to convert signals to +-5V. 

But when I run the SPI code for interfacing with the ADC I seem to only get the first 12bits as a constant value.The remaining 12 bits are just changing randomly.

Vref for ADC is 5V.

My Vdrive = 2.5V

DVDD = 2.5 V

AVDD = 2.5 V

Mclk is 1MhZ oscillator

Sclk I have tried all frequencies(from 100kHz upto 6MHz)Still no luck.

 

I also checked on the DSO,the SDO line gives only data12 bits.The remaining bits are just noise.

So that expains why I am getting 12bits on my SPI interface.

But what is the reason for getting only 12bit data.

 

Please find attached below the schematic.

Thanks 

Reagrds

Husain#

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