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On AD7779 is there something special on CH0 that other do not have ?

Question asked by ndomblides on Feb 21, 2017
Latest reply on Feb 24, 2017 by ndomblides

Hello,

 

I'm evaluating the AD7779 using a custom microcontroler board. I'm using 4 Sigma delta Channels (CH0 to CH3) and I have somme problems with CH0.

First of all, I would like to configure all channels with PGA=4. I modify the CH0_CONFIG register to be equal to 0x80, as CH1 to CH3 register.

I convert data and all channels except CH0 ive me the input voltage value increased with correct PGA gain. CH0 give me value with unity gain.

 

I changed the configuration read back 280mV reference voltage. Ones more, all channels give me a slightly correct value except Channel 0, The read value seems to correspond to input voltage value !

 

Where the problem can come from ?

Why my PGA cannot be configured correctly for CH0 but can be for others ?

is it possible that internal mux for channel 0 does not work anymore ?

 

Thank you for your help !

 

Nicolas

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