we are using AD7190 as ADC for load cell transmitter.
In some situation ( in industrial environment ) the ADC latch up .
This is our schematic :
I have read this from AD7799 faq :
"The maximum dc current that these protection diodes can withstand is
10 mA. Therefore, the maximum current that can be applied to any input
is 10 mA. If it is possible for a current in excess of 10 mA to be applied
to a pin due to an overvoltage, external protection is required. Protection
schemes that can be applied include transzorbs on the power supply lines,
series resistors on digital input lines, and resistors and diodes on analog
inputs. For example, the external protection could be a resistor in series
with the input pin to limit the current into the pin to less than 10 mA. For
example, if the maximum overvoltage applied to a pin will be 5 V, a 1 kΩ
series resistor in each line will limit the current to 5 mA."
I have use SMBJ5CA for place between IN(+) and IN(-) .
and when i place this it didn't make any effect on adc result .
but as you know it need to be protected against GND and VCC.
Kik this :
But when I add D2 and D3 like above
The adc works nonlinear ! and add offset. (maybe the leakage cause this ).
Is there any specific schottky diode and TVS that you can recommend
that hasn't got these problem ?