I'm having a bit of trouble understanding how this logic level shift circuit works exactly. The design is from Sparkfun.
Hhere is the schematic:
For my application, the LV and HV are the 3.3V and 5V bus respectively. The LV1 and HV1 are the respective logic pins. I have a confident idea on how it works when LV1 is the input and HV1 is the output. However I can't seem to figure out how it works the other way around when HV1 is the input and LV1 is the output.
Here is what I know so far on how the circuit works. If LV1 is high, the voltage potential between LV1 and LV (gate of the N-MOSFET) aka Vgs is zero. Thus the MOSFET is off (open circuit) and HV1 only gets the 5V signal from HV through R4. When LV1 is low, there is a Vgs of 3.3V and the MOSFET turns on. From it, HV1 is at the same voltage potential as LV1 thus it's low.
Is my explanation correct on how the LV1 being the input works? How does the circuit work the other way around when HV1 is the input?