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i.MX53 I2C. Can the device pins supply the I2C standard current?

Question asked by TomE on May 8, 2013
Latest reply on May 15, 2013 by Yuri Muhin
Branched to a new discussion

We have an application with the i.MX53 we're using that needs "as high a speed as possible" over I2C. Both ends of the link (MCF5235 and i.MX53) can be programmed with high speed clocks, but the limiting factor is the rise time of the open-drain I2C bus. That means we need the pullup resistors to be as low as possible, and that is limited by the driver current. The MCF5325 end will sink 5mA (or maybe 25mA, the Data Sheet is a bit confusing).


At the very least we'd like to run at the "I2C Standard" level, which requires the SDC and SCL pins be able to sink 3.0mA.


So the i.MX can sink???


I've looked through the 170 page i.MX53 Data Sheet, and there's no "maximum pin current" specification for the GPIO pins.

The only specification I can find is:


4.3.1 General Purpose I/O (GPIO) DC Parameters

Parameter                   Symbol Test Conditions  Min          Typ Max Unit

High-level output voltage    Voh   Iout = -0.8 mA   OVDD - 0.15   —   —    V

Low-level output voltage     Vol   Iout =  0.8 mA    —            —   0.15 V


That's a lot less than 3mA. If we have to use pullups for that current our speed drops to 1/4 of what we were hoping for.

Do the pins have an undocumented "maximum current" that lets them at least meet the I2C specification?