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RM57L843: I2C clock and data line ringing

Gunter Schmer
Genius 14222 points
Part Number: RM57L843

Hi,

we are seeing some ringing on the rising edge of the I2C clock and data lines of the RM57L843. The behavior looks strange as we were expecting a pure open drain charging ramp. However what we are seeing seems to be a brief period where the Hercules is driving these lines high, then it is followed by the normal charging ramp. Is there something in the I2C buffer configuration that can be changed to avoid this?

Have you seen this?

Thanks!

--Gunter

  • 0
    TI__Guru**** 197126 points

    Hello,

    The ringing might be caused by the reflection. The unmatched impedance of transmission lines can cause reflections. The source’s impedance needs to match the impedance of the trace and the load. Matching the impedance can be accomplished by adding a resistor near the source.  Keeping traces short is another way to combat reflections and ringing.

    I suggest to use pull-up resistors with lower values, for example 2.2kohms.