ADN4651 does not work when TVS diode connected to the data line

Question

Hello, 
 
 I have the following schematic using ADN4651 LVDS isolator:

The circuit works when all the TVS diodes are disconnected. When the TVS diodes are assembled the circuit does not work so I started removing the diodes one by one until it seems like the problem is with D2 and D4. 
 Thus, the circuit works with the TVS diodes but only if D2 and D4 are unassembled. 
 What could be the problem?

ConalW · Accepted Answer

Hello, 
 This does seem unusual. Channel 1 and Channel 2 should behave the same way, and in any case the TVS per the details you provided should be suitable for high-speed operation. I see the TVS capacitance is 17pF typical, 22 pf max. You could try placing this capacitance where you removed D2 and D4 to see if that is enough to stop the circuit operating again (i.e. the issue is the TVS capacitance). There are TVS options with lower capacitance than that specific model. 
 Can you confirm what parts/circuits are connected on either side (Serializer/Deserializer?) in case it's possible those are being affected in some way by the TVS. 
 Best regards, 
 Conal

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ADN4651 does not work when TVS diode connected to the data line

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