My PCB board have several ADuCM360 ADC communicating to the host micro controller. All ADCs individually are having decoupling capacitors suggested by datasheet. We have seen the following observation w.r.t. the ENOB performance. Please suggest the reason.
1. When we wired only one ADC on PCB and evaluated ENOB for worst case (highest data rate, and gain) we got min. 7bits. Subsequently all other ADCs were also wired. Again the ENOB performance was evaluated for the same worst cases but ENOB came out to be min. 9 bits(which is better). What reason can be attributed to this behavior on board. All other decoupling caps like for power and for host microcontroller remains same in both the cases.
I will really appreciate early reply.
Thanks and Regards