I use tow ads8668 for sampling 16 channels of AC analog input with a ±10.24-V input range by daisy chaining。I select the internal reference, the
REFSEL pin be tied low or connected to AGND. So，the voltage of the pin of refio should be 4.096v，but infact it is 3.77v and 4.4v。and the sampling voltage uplimt lower than the reference volatage（2.5x4.096）.I dont know the cause，please help me 。
Hello,
The REFIO should measure at 4.096V. What is the voltage measurement at REFCAP pin?
What capacitor size is placed at REFIO pin and the REFCAP pin?
Each pin needs a minimum of 10uF capacitor decoupled to REFGND, please see image below.
Since you are daisy chaining the devices,is each device configured to use its internal reference? Or does the first device output its reference to the second device in the chain?
Regards, Cynthia
