I am using ADM3251E for RS-232 and ADM2587 for RS-485 on a single PCB with one DB-9 connector on the isolated side. ADM3251E does have one GND2 pin 11 on the isolated side while ADM2587 does have 4 GND2 pins on the isolated side. I am using one common ground on the isolated side with ADM3251E pin 11 and ADM2587 pin 16 and 20 connected to this GND2(ISO). The Stitching capacitor on the ADM3251E goes between the GND and GND2(ISO) pin 11. While on the ADM2587 the Stitching capacitor is recommended to be connected between GND and GND2(ISO) pins 11 and 14.
How can I use one embedded stitching capacitor for both of these devices? I am trying to achieve a Class B compliant low noise design. What is going to be my arrangement for the ADM2587 pins 11, 14, 16, 20 and ADM3251E pin 11 for using one stitching capacitor for both to get a Class B compliant design.