Optimizing Precision Photodiode Sensor Circuit Design-keep-out around the trace calculation

[hioyo]

I am going through this document from Analog devices to learn more about different guarding methods.(https://www.analog.com/en/technical...ecision-photodiode-sensor-circuit-design.html)

In "DC Considerations" paragraph-3 you can see the statement given below.

"One way to minimize this external leakage path is to increase the resistance between the trace carrying the photodiode current and any other traces. This can be as simple as adding a large routing keep-out around the trace to increase the distance to other traces"

My question is how to calculate the required keep-out around the trace.

May I know is there any math or thumb rule to calculate the keep-out around the trace.

 

[betwixt]

No specific calculation as far as I know but the principle to distance the trace as much as possible is good to prevent conduction through the substrate and especially over it surface. If feasible you could cut a slot around the track but that could cause mechanical problems.

Brian.

 

[KlausST]

Hi,

I agrre, I guees it's impossible to calculate:
it depends on: temperature, material, coating, dirt, humidity, aging...

so the bigger the gap, the better. Or: a guarding.

Klaus

 

[hioyo]

Hi Team,

Thank you very much.
I am planning to provide 2mm clearance on both sides of the trace.

Regards
HARI