Q
Can the parts tolerate the 60V overvoltage if the input current is limited to
~6mA by using a 10kOhm resistor ? Does this have any impact to the specs ? Will
the aging be faster ? (According to the absolute maximum ratings AIN/Digital
input current could be 10mA.)
Does the input current and input current drift figures (AD7190, page 4 and
AD7793, page 3) include all input current components ? They are asking this
because some manufacturer specify separately the input current of the ADC and
the leakage current of the protection diodes.
A
The figures on page 4 (AD7190) or page 3 (AD7793) refer to voltages and
currents for normal operation.
If you go outside those limits the converters no longer work to specification,
but if you come back within them all is well again.
The figures in the Absolute Maximum tables on page 9 (AD7190) or page 8
(AD7793) MUST NOT be exceeded. If the only protection is a current limiting
resistor the substrate current which flows when the input diodes conduct may
corrupt the data in the various device registers. The device should always be
reset and data reloaded after an input over-voltage event.
If the currents are limited to 6 mA the long-term effects should be minimal if
the over-voltage is occasional, but if it happens too regularly there may be
some long term effects. I do suggest that you use external protective schottky
diodes as well as the ADC's own protection.
