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AD8556 Programming problem

Question asked by JMKim on Dec 6, 2011

Hi, there,

 

I just started to use AD8556 for my sensor board.

To get the maximum total gain, I tried to program theAD8556 like this.

Second stage Gain = 7, First stage Gain = 127, Offset = 0x40.

 

0x40 for Offset setting is just for checking easily whether the programming works fine. No other meaning. Will be changed to much lower value after the validation.

 

When I tried to simulate Offset Setting, it worked fine.This means writing code it self is OK.

When I programmed Second, First and the Offset in a row, sometimes it worked, but not always.

 

Is there anyone who can tell me about what's wrong?

 

The output of the AD8556 will be fed into 24bit ADC as a Single-Ended signal. To get maximum dynamic range dyring the AD Conversion, I want to keep the Offset of the AD8556 as low as possible, as the ADC have another 128x FPGA amp inside.

 

To handle the very weak signal from the sensor, I want to use full Gains at AD8556 and ADC, which can result in 1280x128 Gain.

Thanks in advance.

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