Can i use At24C256N-10SI 1.8 , directly on a 5v Mega32

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Guyzz

I have gotten some At24C256N-10SI 1.8 - Atmel 256K I2C EEProms .....
I goofed in the order :oops: :oops:
And ordered 1.8v SOIC instead of 2.7v PDIP :? :?

They are rated 1.8v and the datasheet says 1.8 to 3.6v , but later on it says max voltage 6.5v.

http://www.atmel.com/dyn/resourc...

I was wondering if the ones i got can be used in a 5v environment , and that the 1.8v markings just means that it is also able to run at low power.

To me it seems like that might be the correct assumption , but as it is going to be my first I2C experience , i would like not to fight both my code , and a "Toasted chip".

If someone has any experience here or would be kind enough to have a look in the datasheet.

I will be using it for a Mega32-5v and prob on a Breadboard , after soldering it on a 8-Pin PDIP Socket :oops: :cry:

/Bingo

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Hmmm....

Was the question so "far out" .... 8)

/Bingo

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I would not run the AT24C256N at 5V; the 6.5V value you mentioned (actually, the datasheet says 6.25V) is an absolute maximum rating, not normal operation. That said, you do have a possible solution. I2C outputs are open drain and are pulled up with external resistors. If you don't mind adding a second supply at 3.3V you could run the AT24C256N at 3.3V and the AVR at 5V. The SDA and SCL lines would be pulled up to the 3.3V supply. You didn't say which AVR, so I used the M128 datasheet as a reference. For the M128, Vih is 0.6 * VCC or 3.0V. Since you would be pulled up to 3.3V, this would give you logic levels that both devices an operate with. You will need to be careful with your programming; if you ever configured the SDA or SCL lines on the AVR as normal outputs, you would be exceeding the recommended Vih on the AT24C256N. You might consider adding some protection, such as a clamping diode.

Dave

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You should never run the EEPROM at higher voltages than 3.6V.
There's a big difference between Absolute Maximum Voltage and Operating Voltage.
Absolute Maximum Voltage is just the it can handle without getting damanged, but it cannot operate at this voltage.

Power the EEPROM at 3.3V and add this voltage translator:
It's a very simple and good 5V to 3.3 V I2C voltage translator.
http://www.edn.com/article/CA193...
Open the PDF document and read the article named "Two-transistor circuit replaces IC", then you will see the schematics inside the text.
For your purpose you can just connect enable directly to 3.3V (not 5V)so it's always enabled. The enable pin is only used to make it hot-swappable, but I don't think you need this feature.
Remember you need such a circuit at both the SCL and the SDA line.

You could also use a more simple solution with only one MOSFET and two pull-up resistors at each line, but maybe it will be cheaper with two bipolar transistors than one MOSFET.

http://www.semiconductors.philip...

More detailed description of the level shifter at section 18.1 in "The I2C-bus specification":
http://www.semiconductors.philip...