I need to level shift a 3.3v digital signal to 5.8v at around 1MHz. The circuit below works but the power consumption is very high. Can anyone suggest a modification which will still allow the bandwidth but bring the power consumption down?
Adding resistors to the PFET VCC input and NFET GND output does reduce it but I can't find the right balance between slew rate and consumption.
I've looked at the internals of some off the shelf level shifters but am struggling to understand how they manage it.
Best Answer
Allow me to share with you the circuit of a levelshifter as is used in many ICs:
simulate this circuit – Schematic created using CircuitLab
It uses 8 transistors, which looks like a lot.
But this is what is used on a chip so transistors can be made extremely small. On a chip this can be made to work up to GHz frequencies. When static (the input signal does not change) the circuit consumes no current.
It is nearly impossible to build this circuit on a PCB using discrete MOSFETs and get similar performance, you'll be lucky to make it work at 10 MHz. Discrete MOSFETs aren't designed to be used like this.
Fortunately chip manufacturers put this circuit (or something similar) on a chip for you to use. Just search for "levelshifter" and you should find a suitable chip to do the job.