Is this kind of interface possible with i2c?

[arunb]

hi,

I am trying to interface the mcp23016 in this way.

The mcp23016 supply pin is connected to 5v DC line. The pullups to the I2C pins are connected to 3.3 VDC. A 3.3 v mcu is connected to the i2c bus, the supply pins of the mcu is connected to the 3.3 VDC line.

Will the above system work?

thanks
a

[jeremiah]

According to the data sheet for your IO expander, a value of 0.8VDD (0.8*5v = 4v) is required for a logic high, so the pullups won't be able to drive the lines high enough for the mcp23016 to see a high all the time.

Why not run the mcp23016 at 3.3v as well? It allows for a wide voltage range on the data sheet.

[Ttelmah]

But of course, if you must use 5v, 'possible', yes, using level translators. Either simple FETs, or for faster performance IC's.

Best Wishes

[arunb]

thanks for the reply. I see the point.

The mcp outputs need to drive 5v, so running the mcp on 3v will not work.

Of course i could use fets as suggested.

thanks
a