I'm developing an analog input module based on TI's ADS8668 and want to protect the input channels from over-voltage. According to the datasheet, each analog input channel withstands voltages from -20V up to +20V.
Although my analog signals are expected to be in the range of 0-10V, wrongly connected inputs (e.g. miswiring) could lead to voltages up to +24V on the ADC input channel.
To protect my analog inputs, I tend to use Schottky diodes, as recommended by TI (Engineer It: How to Design Protection Circuits for Analog I/O Modules) and Analog Devices (Protecting ADC Inputs).
I have no supply rail in 10-20V range on my PCB, that I can clamp my diodes to. Therefore I would just place a Zener diode (D3) as shown below, to protect my analog inputs from voltages above Zener voltage.
Simulating this schematic in LT Spice using a 12V Zener results in a system behaviour according to my requirements (see below).
Is it sufficient (and good practice) to clamp my Schottky diode (D2) to the Zener diode without having any positive supply rail (unlike this solution, which uses a shunt regulator)?
Is there anything I need to beware of, especially the power dissipation of my components in an over-voltage case?
Thanks in advance!