In our current design, we have two devices which communicate with each other using I2C. But their I2C logic levels are different, so we need to use a level translation?
Can I use a simple level translator for this?
I have chosen this part MAX13003
http://datasheets.maximintegrated.com/en/ds/MAX13000E-MAX13005E.pdf
Electronic – I2C Level translation
i2clevel-shifting
Related Solutions
I've designed a small system that might work for your particular application. Here is the schematic:
I forgot the reference node, it must be connected to terminal 2 of BT1. How does this work?
From high to low
First of all let's assume we can neglect the current flowing in/from "low".
When high is pulled up (5V) in R1 no current flows, while the three diodes are conducting. Assuming a forward drop voltage of 0.6V the voltage at low will be 3.2V, and the current flowing from high will be approximately 320uA.
When high is pulled down (0V) all the diodes are interdicted, so the voltage at low will be pulled down by R2. The current that high must sink is approximately 500uA.
From low to high
Now let's assume high is not consuming current.
When low is pulled up (3.3V) the diodes can not conduct because the voltage at high would be more than 5V, so high is pulled up by R1, the diodes are off and low must provide about 330uA.
When low is pulled down (0V) the diodes are correctly polarized, R2 has zero volt across, the voltage at high is about 1.8V and the current sunk by low is approximately 180uA.
As you can see, the big problem is that 1.8V is a bit too much: a CMOS circuit would probably read that "low", while a TTL is likely to read that "high". A better approach could use a 1.5V zener diode instead of the three small signal diodes, with the cathode connected to R1 and the anode to R2. The resistor will probably need to be reduced to meet the minimum polarization current of the zener diode.
One last thing about the resitors is that you can use any value from 1k to 100k, of course higher resistance values correspond to lower current consumption, but also to slower transient response, and vice versa.
Yep, this will work just fine. Here is a great article on voltage level translation that Anindo Ghosh shared with me that explains all the different types of voltage translators: http://www.ti.com/lit/an/scea035a/scea035a.pdf
Logic Level = Voltage Level
In a 5v system, 5v(voltage) is high(logic) and 0v(voltage) is low(logic) and same for 3.3v...
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Best Answer
It can be easy to level shift the I2C signals between two voltage domains using any one of a number of different buffer parts that are made specifically for this purpose. However for most applications there is another discrete solution that works very well as shown below.
This solution will be lower cost to implement as long as you do not need additional buffering of the I2C bus. If buffering for long buses or excess capacitance or going between boards is needed then it is recommended to look into the chip type buffer solution.
You can gain additional information and understanding from the NXP (formerly Philips) application note on Bi-directional Level Shifters.