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ADS1235: Identifying overvoltage conditions

Tool/software:

I was reading the forum post [ [FAQ] Delta-sigma ADC anti-aliasing filter component selection] and the following 

"To determine the allowable voltage drop across this resistor, use the expected overvoltage conditions seen at the system input (VOV)..."

I'm unsure how to determine the overvoltage conditions or even what it is referring to, I'd appreciate it if someone could give me a clarification on this,

Thank in advance,

Gabríel Snær Völuon

  • Hi Gabriel Voluson,

    Overvoltage is in most cases a failure event that exposes the system to voltages >absolute maximumi.e. an event that can occur in your system but is not part of the normal operating conditions. For example, if you have a 24V power supply in your system and it is possible the end user could miswire the ADC inputs such that they mistakenly apply 24V to the inputs, this is an overvoltage event. Comparatively, if you want to measure +10V in your system, this is not an overvoltage event even though 10V is outside of the range of the ADC inputs. You would accommodate this signal by attenuating the inputs (resistor divider, diff amp) before they reach the inputs.

    In the former case, you would size your components to protect against the 24V miswire event. Note that in this example, it is possible this is a sustained event, as the person wiring the system might not realize right away that the miswiring occurred, and therefore the system could be exposed to the high voltage for seconds, minutes, or even hours. This is different compared to a large transient event that would be over in micro- to milliseconds. You would account for such an event using a TVS diode, or similar component

    -Bryan