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UART level translation, what type of translation IC is required?

I have two devices, and need to figure out how to translate between them for 2 wire UART.

U-Blox NEO-5G, 1.8V
Input low:  0.22V (MAX)
Input high: 0.91V (MIN)
Output low:  0.4V (MAX)
Output high: 1.4V (MIN)

Telit GC864
Input low:  0 - 0.5V
Input high: 2.1 - 3.3V
Output low:   0 - 0.35V
Output high: 2.2 - 3.0V

UBlox -> Telit
LOW: .4V (MAX) -> 0-0.5V   (WORKS)
HIGH: 1.4V (MIN) -> 2.1-3.3V (DOES NOT WORK)

Telit -> UBlox
LOW: 0-0.35V -> 0.22V (MAX) (DOES NOT WORK)
HIGH: 2.2-3.0V -> .91V (MIN) (WORKS) 

So i obviously need a level converter of some sorts.
What type of converter is needed?  CMOS?  If so how do I select the voltages?


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used an I2C translator for 1.8 to 3.3 V

works great.  thanks guys!

A Google search for 1.8 volt to 3.3 volt level shifter turned up Fairchild Bidirectional Level Translators.

The 74VCX164245 does appear to be a part that can be sampled, best in a TSSOP package that would be a little challenging to solder. Might look for a Schmart board to prototype it with.

 Also might look for other devices available, or possible level translation circuits. (involving a couple transistors as has been discussed in a recent I2C thread.) 

What you need is the ST232 (for 5VDC) or the MAX232 (for 3.3vdc). Just grab a ST232 and call it good.

Well the U-Blox is a 1.8v device so I don't think it would be possible for the high to be 3V.  I assume connections won't work because their ranges differ too much (by specification anyway).

I previously tried a direct connection between the devices but did not have any luck.  This, of course, could be a software issue.

I will test the output voltages.  I have a basic volt meter, will see what kind of numbers it gives me.

Still if the spec claims such a variation of voltages, even if the setup works once how am I guaranteed it will work with a different batch of the chips (ie same components but bought at different times or bought in volume)?  I feel like there should be a more concrete solution.

How do you know " (DOES NOT WORK) ".
Have you connected the devices and tried it.

U-Blox Ouput High will never be less than 1.4V. It may actually be 3V.
Have you measured the output voltages ?

You are getting the specifications confused. You may not need a converter.