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During RF Immunity (IEC 61000-4-3) test. The OP AMP inside my product just output a low frequency signal every 3 seconds upon each step starts. Anybody help??? Thanks!!!!!
You don't tell anything about cables, most important things in radiated susceptibility. Try separate them apart one another, try twisting or better shielding them, try to add a filter to the power supply cable.
From my experience it is better to :
- use differential input to your amplifier
- use emi filter common mode chokes and ferrite bead to filter signal from input (should be placed as close as possible to input cable entry to pcb)
- use minimum trace width on pcb for your analog parts
- extensive use of ground plane
- filter power supply coming to your analog part
- use better opamp with higher cmrr (for dfferential input scheme)
- use smd components with low physical height
- pay attention also to that opamp output is not exposed to em field as well .
Perhaps shielding is also possible but it has to be justified.
hi as u said u r opamp is mis behaving
u can try making its gnd strong to earth
and u can also try placing some metal strip (or some ferrite strips available)
near to ic connecting to gnd, if this improves u r problem u can think something in that way to suppress the noise
if can check the pcb design of Iphone they have a metal strip sheilds all around the ic's, this helps in most cases
if u still have the same problem try to figure out the ic properties
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