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Aduc7060 PGA doesn't working

Question asked by jojogaspar on Mar 9, 2011
Latest reply on Mar 10, 2011 by jojogaspar

Hi,

 

I'm using the ADUC7060 in a new design and I have some problems to use the PGA.

 

The configuration of the primary ADC is:


     - ADC1/ADC5 selected (single ended)
     - internal reference


 

when I perform ADC acquisitions I get on ADC1 the following results:

 

     A continous signal of 120 mV (Operational amplifier output) is applied between ADC1 and ADC5

 

     - If PGA = 1          ADC0DAT = 0x194000                  ---> 118 mV OK

     - if PGA = 2          ADC0DAT = 0x327000                  ---> 118 mV OK

     - if PGA = 4          ADC0DAT =  0x2C7000                  --->  52 mV  NOT OK

     - if PGA = 8          ADC0DAT = 0x323000                   ---> 29 mV  NOT OK

 

     A continous signal of 18 mV (Operational amplifier output) is applied between ADC1 and ADC5

 

     - if PGA = 16        ADC0DAT =  0xA7000                      ---> 3 mV  NOT OK

     - if PGA = 32        ADC0DAT =  0xB4000                     ---> 1.6 mV NOT OK

     - if PGA = 64        ADC0DAT =  0xBB000                    --->  0.86 mV NOT OK

 

 

Regards

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