i implemented in our new product about 10 nodes with the ADM2682E.
The bus we use is a 4 wire bus full-duplex and terminated at it's ends with 120ohm.
EMI tests on the system shows that we have big problems around 400MHz.
AN-0971 and also AN-1109 were read after the first prototype was ready,
so i followed only the recommendations which were given in the datasheet (figure 41 REV B)
So my problem now is how should i go on.
First steps that i will try :
- implementing a 5V to 3,3V supply for the ADM2682E
- stitching capacitor but the calculation result of this will only be 27pF due to the fact that i've no place on the pcb
- pcb itself is a 4layer, is it better to change to a 6 layer
At the EMI measuring institute we try to solve it with Y-capacitors between GND and ISOGND, 5V and 3V3ISO.
The capacitors have 150pF, the result was good. But for the series it is not a solution.
Could you give me any advice ?