I have an application where I will be taking serial signals will need to level shift the signal to 3.3V. The input signal will be from 15 to 5V for a high input and I need them all shifted down to 3.3V.
I understand how to do this when there is one constant input voltage but in this situation, depending on what is connected to my RS232 connector I could have..
-10 to 10V
0 to 5V
0 to 15V
on the input side. Does anyone know a good option to make sure that all of these 3 different signals can be shifted down to 0-3.3V?
I'm struggling to find a solution.
Thanks in advance
Best Answer
A simple clamping circuit would do the trick. The diodes will make sure the voltage seen by the buffer is never more than 3.3+Vd and never less than 0-Vd (where Vd is the diode forward voltage). Additionally, the 1K resistor provided current limiting.
simulate this circuit – Schematic created using CircuitLab