The responce of AD637 when the large signal is came

Question

Dear Sir/Madam, 
 I just use your AD637 RMS to DC converter. Input is the sound signal. CAV is put 100uF capacitor. When the large sound is inputed to AD637 Vin momentarily,we just found to output pulse-signal. So the analog meter that is put the RMSOUT-pin was shaked off. So I replaced the CAV capacitor 100uF to 2.2uF. Then this trouble was fixed. I have a question. Why this trouble was happen? I would like to know the reason why. 
 Thanks, Kaos

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ADIApproved · Answer

Hi Kaos, 
 Thanks for using the AD637 and sorry to hear of your difficulty. Unfortunately there could be a great many things happening and without further knowledege of your circuit and the nature of the input signal. I can't be sure of the specific problem. Here are some thoughts, however. 
 1. If you used 100uF, it must be a polarized capacitor of some kind. If this is the case, be sure that you connected the capacitor so that the polarith is correct (+ should connect to the output). 
 2. 100uF will give you very good low frequency response but will also increase the settling time. If you are sampling the output, there may be a sampling issue of some sort. 
 3. When the large signal is applied, is it a momentary sound? Continuous? 
 4.Please remember that the averaging capacitor functions to averae a certain number of cyclical period to yield a dc voltage. If you are trying to detect a large burst, the output won't be continuous. 
 I hope this helps. 
 Best, 
 js