Maximum output current on CM pin?

Question

Hi everyone 
 I am actually using the CM pin of ADAU1361 as the negative input on a AOP differential amplifier. 
 The impedance seen from the CM pin is around 40 kohm. The CM pin is also connected to LIN_P input pin. 
 As a result, the CM voltage is not stable, around 1 to 1,4 V between different products, instead of 1,65V (AVdd/2). 
 
 Is the current consumption too much for that pin? Is the impedance of my AOP amplifier too low? 
 I did not find the answer on the forum...Sorry 
 
 Thanks a lot!

DaveThib · Accepted Answer

Hello Etiounne, 
 Thanks for looking around on the forum. The answer is probably somewhere but it can be difficult to find if the question was not only this question. I probably could not find it either! 
 The CM pin will have around a 5k output impedance so yes, a 40k load is a little too much (too low). I would use an Opamp in a voltage follower configuration with the input to the positive pin and use an Opamp with a fet style of input circuitry. Not bypolar differential. 
 This should show an improvement for you. 
 Dave T)

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Maximum output current on CM pin?