How does the ADAU1979 and AD9212 handle signals below 10hz?

Hi Buzz,

The ADAU1979 is an ADC that is designed for audio application i.e. 20Hz to 20KHz BW. However the ADC could be used for signals below 10Hz with some limitations. 

The ADC performance is tested for the 20Hz to 20KHz BW in the DS. so the specifications are valid for this BW only. If using below 10Hz, the noise spec might not be same. 

The AC input coupling capacitor for the analog inputs might need to be adjusted for the desired BW The input impedance for the ADC is specified in DS and can be used along with the source impedance of the tachometer to calculate the input coupling capacitor value. 

Is the tachometer output single ended or differential? Depending on the configuration the tachometer output, the ADC input connections will need be set up. I would recommend to use the differential input configuration to reject the common mode noise at the inputs. 

The full scale output level of your tachometer should match the ADC full scale input to prevent the clipping of signals.

Regards

Rajeev

Ok, sorry for my delay.  My real problem is how do I remove this large impulse around 0hz?  Is there a way to do it using the registers?

Ok, sorry for my delay.  My real problem is how do I remove this large impulse around 0hz?  Is there a way to do it using the registers?