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Can i2c communication work w/ 2 device of diff. VCC

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arup

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Dear Sir,

I am having 2 devices On i2c bus .One is MCU with VCC = 5.0V and another
device with VCC = 3.3 V. Is it possible to have i2c communication between 2 devices in this case ??
Pls help.

Thanks

Arup
 

Dear Sir,

What i mean to say in my earlier post is that i want have i2c communication between two devices.One of them supplied from 3.3V DC and another from 5.0V DC.Now please tell me are they will be communicate on i2c bus without any external ckt on i2c bus.

Pls HELP

Thanks,
Arup
 

Nope .. u need a logic converter ..
 

Hi,
Is ur I2C master 5V or 3V
Thanks
 

Check the datasheet of the 3.3V I2C device and see if it's I/O pins are 5 volt tolerant .Then you can use it with the 5v I2C device
 

Yes. In the past, I have used the GTL2022 from Philips to convert the levels. **broken link removed**
 

arup said:
I am having 2 devices On i2c bus .One is MCU with VCC = 5.0V and another
device with VCC = 3.3 V. Is it possible to have i2c communication between 2 devices in this case ??
Click to expand...

50_1164737455.jpg


Philips Semiconductors: AN97055
 

I think all you need to do is tie the pullup resistors to the +3.3V supply amd simply connect the I2C lines of the two devices together.
That way you are sure that the 3.3V device will not get damaged.
And the inputs of the 5V-powered device will accept the 3.3V levels, since the input buffer thresholds are less than 3.3V.

What you are showing will most likely work, but when the 5V device sends data on the bus, you will have drops across the body diodes of the MOSFETs, which will affect the LOW levels.

Try what I suggested above, it should work.
 

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