I'm designing around an AD2S1210 and would like to incorporate some additional protection circuitry for lighting strike survivability. What does the internal input protection of the AD2S1210 look like on the Sin/Cos lines?
There are protection diodes on the SIN/COS inputs to the AD2S1210. This is an ESD protection circuit that comprises of clamp diodes to VCC and GND at the input. This will effectively clamp the level at the pin to either VDD or GND if the applied voltage exceeds of either of these limits. In addition, a series polysilicon resistor is connected after the input pin that serves not only as a current-limiting component but also it can slightly increase the ESD pulse rise time, giving more time for the protection diodes to react.
Hope this helps.
While the protection diodes at the inputs can help protect the device from a few "normal" est events, A lightening strike can often produce more energy than the on-die protect against. Having said that, if you are considering induced current from a lightening strike in the vicinity of the product, the on-chip protection might be sufficient. However, if you are considering a direct strike of the equipment, than the protection becomes much more complex and really beyond the scope of a forum like this as you will e concerned about the entire system, not just a single component.
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