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Drift issue with AD8436 RMS-DC convertor

Question asked by Dave10 on Mar 29, 2017
Latest reply on Mar 31, 2017 by Dave10

Hi

 

I have been testing the AD8436 RMS-DC convertor with a signal generator upon the bench and have found the Voltage level drifts downwards overtime for some reason.

I have tested the device with a 500mV  input sine wave at 10 Khz's but cannot seem to get a stable reading when measured every 3 seconds.

The device is being powered with +/- 5V rails and is connected as per the datasheet for the basic configuration.

I have fitted the following external components.

 

Cin, capacitor set to 200nF  as selected from the application data sheet.

CAVG   Set to 20nF also selected from the datasheet.

CCF         Not fitted.

 

The CLPF (output capacitor is currently 100nF, although I have tried values upto 2.2uF). I found by adding a larger capacitor just leads to the device needing a longer settle time when the device is initially powered).

 

The device is interfaced  to a 16 bit ADC convertor which I have tested independently and this was found to be functioning correctly.

 

How can I stop the device from drifting and give a stable output for the frequency range that I require ?

I would like to use a frequency range of between (8-16 Khz's).

How much will the dc level change across the frequency range at a stable temperature ?

 

Any support is greatly appreciated !

 

Regards Dave

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