I recently had a pcb made with the following input path to one of the ADC pins of an atmega168:
(see attached)
Input jack (with normal to gnd)-->inverting opamp(gain 0.5)--->inverting opamp (gain 1)--->shottky diodes to +5V and Gnd---->ADC pin.
I totally forgot to put a current limiting resistor before the shottky diodes but I am wondering if it is needed?
The expected input is 0-10V (which gets reduced to 0-5v)
The max overvoltage possible (accidental at input) is 15V (so 2.5V over at the shottkys).
Do I need to hack my pcb to add something like a 4.7K resistor in the before the shottky or can I leave it as is?
I am worried about damaging the AVR ADC input (which afaik has an internal input resistor)
I guess also ruin the opamp/shottky if there is an overvoltage and nothing to limit the current flowing through them?
(see attached)
Input jack (with normal to gnd)-->inverting opamp(gain 0.5)--->inverting opamp (gain 1)--->shottky diodes to +5V and Gnd---->ADC pin.
I totally forgot to put a current limiting resistor before the shottky diodes but I am wondering if it is needed?
The expected input is 0-10V (which gets reduced to 0-5v)
The max overvoltage possible (accidental at input) is 15V (so 2.5V over at the shottkys).
Do I need to hack my pcb to add something like a 4.7K resistor in the before the shottky or can I leave it as is?
I am worried about damaging the AVR ADC input (which afaik has an internal input resistor)
I guess also ruin the opamp/shottky if there is an overvoltage and nothing to limit the current flowing through them?
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