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Allowed I2C rise- and fall-times

Question asked by Roland Strommer on Sep 6, 2017
Latest reply on Dec 11, 2017 by CM Tan

Hi all,

i have a question about the allowed fall-times of I2C-signals of the NFC-driver NT3H2111W0FHK.

 

In the linked document "I2C-bus specification and user manual" UM10204 (Rev. 6 - 4 April 2014) one can find different allowed rise- and fall-times for the signals depending on the used mode (which makes sense so far):

 

 

But why are limits for minimum fall-times only defined in some cases but not in other?

Currently the standard-mode allows faster fall times than fast-mode or fast-mode plus. The minimum limits for rise-times are even stranger: standard-mode and fast-mode plus support faster rise-times than fast mode.

 

In our application (fast-mode) the measured fall time is only about 3-5ns - but the minimum allowed fall time according the spec would be 10ns. - Could this cause any issues?

 

We could change the communication speed and would be fine with the limits but this would waste valuable time if this measure is not absolutely necessary.

 

Thanks,

Roland

 

P.S. footnote [1] seems to be incorrect: VIHmin is lower than VILmax.

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