Level Translator for AVR and microSD

[giorgos3924]

Hello!
I want to connect a microSD card in my AVR ATMEGA32 which its operate with 5V.
The microSD card i think that operates with 3.3V so, it is must to connected via bidirectinal level translator.

I found this TI's translator 1-BIT BIDIRECTIONAL VOLTAGE-LEVEL TRANSLATOR
FOR OPEN-DRAIN AND PUSH-PULL APPLICATIONS
which its accepts any voltage from 1.65V to 3.6V in input A, and 2.3V to 5.5V in input B.

My matter is: Can i direct wire the chip's I/O between AVR and microSD?
or it's only, as the datasheet say, "for open-drain and push-pull applications"?

[paulie]

Make your life easy and run the AVR from 3.3v so no conversion is needed. 5v is an archaic holdover from the early Ardunio days. If you are unable or unwilling to do that then a couple 1k resistors will suffice.

[dannyf]

Can i direct wire the chip's I/O between AVR and microSD?

Fairly easy from the avr/output to the microsd/input.

The other way around will depend on the devices used.

[giorgos3924]

Make your life easy and run the AVR from 3.3v so no conversion is needed. 5v is an archaic holdover from the early Ardunio days. If you are unable or unwilling to do that then a couple 1k resistors will suffice.

in my circuit i have a lot of devices on I2C bus which operate at 5V. Therefore, if i make the AVR to work at 3.3V i think that something will fail.

[hans]

If possible, avoid those self-sensing direction chips. They are prone to oscillating when low pull up (even <10k) resistors are used because they are confused which direction the data is flowing.

I2C is an exception in that most, if not all, devices are open-drain. If the digital inputs on all 5V slaves are TLL you should be good by running the AVR and pull-ups on 3.3V. Devices can only pull the bus to GND via their open-drain switch. They should not power a bus signal to 5V. The open-drain is required because some slave devices want to do clock-stretching.

[miguelvp]

Edit: Forgot to mention that this is for I2C up to 400 Kbits/s not sure how it will work on data faster than that.

Old Philips app note:

http://www.adafruit.com/datasheets/an97055.pdf

New one from NXP (formerly Philips) but I think the old one has more information

http://www.nxp.com/documents/application_note/AN10441.pdf

[sleemanj]

I have no problems with an SD Card just with zener diodes (and resistors) to limit to 3.3v, of course, your mileage may vary, but works for me.

[paulie]

Turns out extra zeners are unnecessary. AVR have them built in. As mentioned earlier 1k resistors are all thats needed. No problem up to couple Mhz.