I2C MOSFET's

[Ed]

Hello,

I need to use a 3.3V device with the 5V I2C bus. In the I2C
specification it recommends using MOSFET's to do the level conversion.
Can anyone recommend any MOSFET's to do it? I need to run at 400KHz.

Thanks,

 

[Fritz Schlunder]

"Ed" <craig.dunn@uwe.ac.uk> wrote in message
news:78cbf006.0312040121.35419f72@posting.google.com...

Hello,

I need to use a 3.3V device with the 5V I2C bus. In the I2C
specification it recommends using MOSFET's to do the level conversion.
Can anyone recommend any MOSFET's to do it? I need to run at 400KHz.

Thanks,

Your post is kind of terse but I assume you are trying to do level shifting
like demonstrated in figure 2 of this document:

http://www.semiconductors.philips.com/acrobat/applicationnotes/AN97055.pdf

If my assumption is true and you are trying to use this most crafty scheme
(it makes use of the integral body diode of the MOSFET) then any small
MOSFET with a low threshold voltage should work. Something like the BSS138
for instance might be a good choice.