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I would like to protect an ADC from ESD and Overvoltage by placing TVS diodes. After a bit of reading, configuration B seem to be the way to go for a differential AC signal. But I'm not competent enough to choose the diodes for this and having 6 of them does not help space/cost wise. So I went ahead and looked for an already-packaged IC, but most configurations of the ready-made ICs are configuration C. Such as TPD2E1B06 for 5V AC differential signal and TPDE007 for 12V AC differential signal; which is perfect for my applications.

Also the series resistor also plays an important role, as I have read that it also reduces the current stress these diodes will receive. At the same time I am using them to step down the voltage signal so I can read the 5V and 12V needed in my application. I would also like to know what would the best placement be in A or D or both but with half resistance.

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  • \$\begingroup\$ Very similar question \$\endgroup\$ – Andy aka Jun 3 at 8:36
  • \$\begingroup\$ What ADC model are you using? What is the permitted input voltage range of that ADC, per input pin (if differential)? What is the supply rail voltage to the ADC? How fast is your signal? What sort of environment do your signal cabling and signal source live in? Do I see R1 and R2 to terminate the line? That would indicate possibly a fast signal to me (RF?) and you might as well want to put the terminator closer to the ADC. What's the input impedance of the ADC? That 1k resistor in series, alone, does not function as a voltage divider. (Add a resistor to ground after this.) \$\endgroup\$ – frr Sep 28 at 20:18
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The C configuration is correct because it presents bidirectional diodes, assuming that your circuit supports and/or uses negative voltage.

Note that all in one packages like the TPDE007 are better than discrete components because they are build for this purpose.

The resistors must be located as in configuration A. You still can add resistors to protect the TVS diodes as in D, but on top of those already in A. But bear in mind that each resistor will distord the signal. If it's a low frequency signal, it's OK. Also don't forget that this resistor set up should or could be present at both trancievers. Which makes not two but four resistors between the two deivces.

More explanations in the datasheets, application notes and guidelines from manufacturers. Worth reading them. Read datasheets for other similar TVS diodes and you will get more informations.

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