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[SOLVED] 1.8V to 5V logic shifter the best option?

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Junior Member level 2
Oct 7, 2012
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Hi i have been looking around in the forum and not really been able to find a concrete answer to this question. I have a GPS module which has a digital IO of 1.8V, this is supposed to communicate to a 5V micro via serial uart.. Fortunately the RX line of the GPS is designed to handle up to 3.35 V so i belive a couple of fast switching diodes woud do the trick, and at a baudrate of 56000 i dont exepct noise problems(please correct me if im wrong). However the TX line of the GRS has to be raised from 1.8V to 5V. I have seen different options to solve this problem but im not sure which to choose. As i see it there is two options:
Using a comperator
This is quite easy, done it many times.. whoever the bandwith, noise, phase and distortion is a big problem here. -Yes this could be done with a precision OPAMP, but those a costly i dont expect it to work well in the highter baudrates ether..

Using mosfet
This is the most prefered idea, and i see it pop op alot of places.. ofcause the gate thresthold voltage has to be lover than 1.8V, but there is plenty of those.. however am i wrong in my understanding that this setup will invert the signal to the micro? is there another setup that will not inverse the signal?

i am on purpose not using a dedicated logic translater ic since it would be silly when its only one channel..

hope you guys can help

Since there is only 1.8V driving the gate, you may need a special kind of mosfet.

Transistors are another option. The base works fine on 1.8 V.

It seems unavoidable that you will need two of them, to get the same polarity signal out as going in.

Screenshot attached.

You can use an logical invert in software and then use just a single transistor stage.
I have done this using Opto-couplers to isolate and level shift between a MCU at 5V and the PC serial port at \[\pm\]12V.

thanks guys, i used the circuit from BradTheRad with success! and thanks for the idea with software invert nitishn5, ill consider using that in my next design:)

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