I am looking to protect an INA849 at 2000 or more gain from high voltages of 30 volts AC at various frequencies. Currently I am using an analog switch IC as the only time the high voltages are sent through the sockets are when the microcontroller commands it, so the INA input pins will be disconnected with IC4 and IC6 when sending the high voltage. An interrupt on the ADC microcontroller pin (net name: Out) will also tell the microcontroller to disable IC6 and IC4 (net name Input Switch) when an overvoltage or undervoltage is detected on the ADC pin. (ADC is set to middle of range, 3.3v microcontroller and ADC, 1.6v on REF pin)
- Is this a suitable protection technique? Should I go for the much more simple (and cheaper BOM-wise) Zener diode approach? I cannot find any schematic for protecting a high gain amp from anything more than electrostatic discharge, or the example in the datasheet with capacitor isolation which will of course remove DC amplification. I can do this if I absolutely must, but I would much rather be able to measure DC as well.
- Will signal integrity be an issue going through these analog switch ICs? Is there a better way to save signal integrity with these voltage transients? Would solid state relays be a better option in place of IC4 and IC6? Would traditional diode and resistor protection be better? (as seen in ADC protection area of the circuit) If so, would zener diodes or a sinkable power supply with Schottky diodes be the best solution for protection?
- Will this be suitable protection from ESD? this will be a device where the sockets are exposed to human contact.(disregard the safety of the high voltage, that won't be an issue as voltages are not sent during socket contact)
Thanks in advance for any potential insights into these issues.