Electronic – 3V3 to 5V level conversion

level-shiftinglevel-translationlogic-level

I'm currently working on the development of some measurement equipment. For conversions I use a small ARM which runs on 3V3 and to display the results I use a graphical display running on 5V. This means that I have to shift the voltage levels from 3V3 to 5V and vice versa.

I have done some research on the topic and found out that there are numerous circuits on stackexchange alone (let go on the whole internet) to do it but I'm interested in how professional developers do it and how to achieve fast switching speeds for fast interfaces.

There is always the option to use a level shifter IC1 but those are expensive and most companies may want to avoid additional component cost. People have done it bidirectional with just a 2N7002 and two resistors[2] whereas other people did it with a transistor and two resistors configured as an inverter.

How do professional developers shift the voltage level from 3V3 to 5V logic and vice versa? I have never seen level converters in a professional product (except for chargepumps for RS232 and such) – Do they just connect 3V3 and 5V logic?

1For example the SN74AVCB164245VR from TI

[2]

circuit

Best Answer

We are using the 4-channel bidirectional TXS0104E in a commercial product, and it is working very well for us.

In our case it is being used to convert from 3.3v to 1.8v and vice versa, but it can also be used to convert from 5v to 3.3v and vice versa (actually the high side can be anywhere from 2.3v to 5.5v, and the low side from 1.65v to 3.6v).

The chip also includes ESD protection on all pins.

It is available from Digi-Key in a 14-TSSOP package for $1.87 in single quantities (73 cents in 1000's). It is also available in an itsy-bitsy (1.9 x 1.4 mm) 12-DSBGA package. That's about the same size as an 0805 resistor. So you can easily fit them inline on top of a parallel bus going between chips. The pins are nicely arranged in order on both sides of the chip to accommodate this.