Our customer is measuring accuracy of AD7655 and please let me know your advice relationship between internal MUX and accuracy.
Our test resul shows large difference (about 50~100LSB) between channel A (INA1 and INA2) and channle B (INB1 and INB2).
So, he has verified as below .
Power supply: 5V
Interface: test using both SPI and parallel
Number of test: 500 ( test is 2pattern which remains A0 = low or high )
Sample: 3 samples
Test result is below
Channle A (IINA1 and INA2) : about 100LSB +- 10LSB
Channle B (INB1 and INB2) :almost 0LSB
( for your information,
in the case of input 1.0V , ( output of ADA4666-2 voltage follower is connected to INA1, INA2 , INB1 and INB2) ,
channle A ＝ 13296LSB (averaged value for 500 time),
channelB = 13230LSB (averaged value for 500 times)
I think that the internal difference between Channel A and B is internal MUX of AD7655.
Does internal MUX affect converted result as above ?
I would like to know if above appearance is in specifaication or AD7655 characteristcs .
And we are checking his circuit design , layout and timing diagram.
Please let me know your advice