AD7476A analog input over-voltage protection

Question

The absolute maximum ratings for the analog input in the AD7476A's datasheet say 0.3V beyond the rails (0V-5V in my case). If the analog signal is driven out of this range by a +/-12V powered op-amp (not ESD!), what is necessary to adequately protect the input? 
 For example, it's a common practice to have a 4.7k or 10k resistor to limit the input current, then have external (to the IC) diodes clamp the voltage to near the rails. In some cases the IC has internal clamping diodes and only the current limiting resistors are necessary. In the case of clamping diodes, since it's only 0.3V that are the absolute maximum, it sounds like I might need some pretty low forward voltage diodes. 
 I look forward to your answers!

KarenNE · Accepted Answer

Hi, 
 Apologies for not getting back quicker. The AD7476A does have ESD protection for the analog input which will start conducting current when the analog input signal exceeds the supply rails by more than 300 mV. Note that the maximum current these diodes can conduct without causing irreversible damage to the part is 10 mA. 
 You may place external Schottky diodes from the input pins to the supplies as well as current limiting resistors. We have a tutorial on Op Amp Output Phase-Reversal and Input Over-Voltage Protection but the protection concepts applies to ADC inputs as well. You may also add transient voltage suppressor to suppress transients. 
 Regards, 
 Karen