Hi,
...almost the same discussion as some days before....
A short signal description:
Sensor output --> buffer input --> buffer output --> PIC input.
Please focus on "PIC
INPUT"
An input does not sink current (in the range of 2mA). 2mA SINK = OUTPUT specification: from PIC_PIN to PIC_GND.
An input is very high ohmic. --> Impossible to draw current in the range of milliAmperes.
Buffer output current is +/- 35mA. Is this is a problem?
This is the MAXIMUM buffer output current. There the true current will be defined by the load = PIC_input. --> maybe in the range of microamperes.
Resistor connected to serially will rectify sink current problem.
"rectify" is not the correct term. What you mean is "limit"
--> A resistor limits the current.
****
With your added buffer you rather increase the fail rate than to decrease it.
* In case your PIC port is defined as "output" both, your PIC and buffer may go defective.
* In case of overvoltage from the sensor lines the buffer may go defective.
****
"For protection"... what does that mean?
The Buffer input will be the same sensitive as a PIC input. Therefore you don´t protect against damage, you just shift the damage form PIC to the buffer.
The costs to change the buffer will be more than the part price.
Isn´t it better to use "true" protection circuit to really prevent something to be damaged?
--> no fail, no need to change a part. --> true cost saving. Better overall reliability. More satisfied customers..
Klaus