Thanks for your guidance,
I think i can remove all SMPS circuits and use LDO instead and keep capacitance less than 13.5uF ... using no inductors too.
Assume my device is I.S (considering all other ATEX specs related to circuit design ...). i still need to connect to two separate Volume converters.
for Isolation, i didn't find I.S Isolated DC/DC converter.
First Solution and Question : If my Device be Designed I.S and can be placed in Zone1 and connect to two Volume Correcters i.e EK220 at same place without Electrical Isolation (Considering current and voltage limitations for voltage and RS232 data lines), this way breaks ATEX rules ?! all considerations about limiting current and voltage are done, but there is no electrical Isolation between two Correcters. is there any rule saying there should be Electrical Isolation ?!
Second Solution:
All devices and connections I.S, Electrical Isolation is done in this way:
Notes:
1- Assume my device is designed I.S
2- The battery voltage 7.2V is connected to V input of Volume corrector after ATEX fuse and Resistor-Zener I.S barrier limiting current and voltage.
3- Relay used is ATEX certified.
4- Opto isolaters are ATEX certified.
5- The RS232 converter after opto isolator is I.S.
6- Relay on and data Exchange between my device and Correcter No1 and No2 is done separately. (Relay1=ON/Relay2=Off and vice versa)
Assume all devices used are ATEX certified, Now question is: does the way of connections used in this scheme match or break ATEX rules ?
Thanks & Best Regards.