Bi-directional 3.3v <-> 5v level shifting...

Wireless & IoT
1

Hiya,

Does anyone know how to achieve this without any extra ‘control’ lines, and/or are there any ICs that do this?

Basically you’ll end up with:

  ______                 ______                   ______
 | 3.3v |          3.3v | lvl  | 5v/TTL          | 5V   |
 |      |---------------|shift |-----------------|      |
 |______|               |______|                 |______|

So the middle black-box will prove transparent lvl shifting…

Cheers,

Mike

Annoying typo, title is 3.3V not 33V

2

http://www.maxim-ic.com/appnotes.cfm/ap … umber/3007

Those do the job nicely… ^^

http://media.maxim-ic.com/images/appnot … 7Fig04.gif

3

You can also just use a single FET as a bidirectional level shifter … like the 3370 but without the extra anhancements. I think either Maxim or TI has an app note on the subject.

4

Use Bus Switches, I’ve used this without any problem when I need have my 3.3v devices talk to my 5v TTL logic.

How to guide.

http://www.idt.com/products/getDoc.cfm?docID=7530

I’ve used IDTQS3245SO part from Mouser.

5

The document wiml was alking about can be found here:

http://www.standardics.philips.com/supp … n97055.pdf

That’s great cause it only needs a singe FET. The pull-ups are in place for the I2C bus, and not required for ‘other’ systems unless their lines are driven open-collector.

6

I bought a bunch of max3378’s to do exactly what you want, arbitrary voltage translation, just set each side to what ever voltage you want (within spec of course)

You may also have luck with the 74LVXC3245, but they have a fixed voltage and are a bit harder to use

7

TI also has an I2C-Bus and SMBus Voltage Level-Translator.

http://focus.ti.com/docs/prod/folders/p … a9306.html

we have used it as an i2c level shifter.

we have also used max3371 for rs232 compatible level translation.

both products are doing their jobs very well. but max3371 [2.2$] is expensive than pca9306 [0.90$]. if you need voltage level conversion for i2c purposes i suggest pca9306 since you need two max ic’s, if you use :slight_smile:

we do not try pca9306 with uart.

8

Hello everybody,

I have the same problem but with one difference, I live in Colombia and some os those components (Max… Mosfets) are not avaliable here so is there any way of doing a translator with simple transistors and resistors?

The document I found here in other topic “Two Transistors Form Bidirectional Level Translator” from Jim Hagerman, Nokia Mobile Phones, San Diego, CA only worked form 5V to 3V but not in the other way. Has someone used it?

9

sebaspc:
Hello everybody,

I have the same problem but with one difference, I live in Colombia and some os those components (Max… Mosfets) are not avaliable here so is there any way of doing a translator with simple transistors and resistors?

The document I found here in other topic “Two Transistors Form Bidirectional Level Translator” from Jim Hagerman, Nokia Mobile Phones, San Diego, CA only worked form 5V to 3V but not in the other way. Has someone used it?

Bidirectional shifting with a few mosfets is possible.

[This is an implementation of [this](http://wwwasic.kip.uni-heidelberg.de/lhcb/Publications/external/AN97055.pdf)](d.holmes > hardware > simple bus level-shift / I2C mosfet level converter w. Fairchild BSS138)

10

Places like [DigiKey will ship to Colombia (of course you end have to pay international shipping rates which are pretty high… :shock: )](http://www.digi-key.com/)