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AD7190/AD7191, questions for input and PGA inside

Question asked by usaghi on Dec 17, 2014
Latest reply on Dec 22, 2014 by MaryMc

Hi,

 

We are now studying AD7190 and AD7191 to be receiving differential voltage output from magnetoresistive current sensor.

So far, AD8421 instrumentation amp is used for the purpose, but considering to ADC integration, AD7190/AD7191 may become a good option worth to be checked.

 

Questions are,

 

Q-1) Could you provide CMRR value of PGA inside which is placing in front of ADC, inside AD7190 and AD7191 ?

 

By looking at block diagram on the datasheet, this PGA Looks like instrumentation amps such as AD8421.

The sensor output voltage range of 0 to 3V but signal can be saveral dozen of uV(micro volts), thus need to be more than 100dB of common mode rejection.

 

In addition, sensor impedance may be in the range of 100K to 300K Ohm.

Gain probably be around 100, so will choose 128.

Signal bandwidth of the sensor output has to be 1KHz maximum.

 

Q-2) May above impedance value of the source (from 100K to 300K Ohm)  bring any problem or additional measures when input to AD7190 and AD7191?

 

Q-3)  Could you please provide current and voltage noise density of the PGA inside AD7190 and AD7191 ?

 

In addition to answers for above questions, if you provide any comments or suggestions, it would be very much appreciated.

 

Best Regards,

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