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Problem with AD7699

Question asked by mole on Feb 3, 2012
Latest reply on Feb 9, 2012 by maithil

Hello!

My name is Nikolay Krotov.  Our  firm have some AD7699 and we try them.  There is  a problem . By datasheet it is 16 bit ADC. We try slowly (constant) signal. So  we take data from ADC with 0.1sec period.

Regime ADC – external  REF = 5.0v. Frequency  SCK = 1MHz (from 0 to 1)

So 

1- we set CNV=0    

2 – we transmit CFG – 14 bit(0x3C51) + 2 bit =0 and simultaneously  we take 16 bit data

3- we set CNV=1 (start new conversion)    

Question:

If signal<1.2v we see LSB bits, but If signal>1.2v three LSB bits are always equal  1? It’s look like it’s 13 bit ADC ! What’s wrong?

 

my email: krotovnick@mail.ru

Nikolay Krotov

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