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MPC8313E I2C Undershoot

Question asked by Heath Dowling on Apr 13, 2015
Latest reply on Apr 13, 2015 by alexander.yakovlev

We are using the MPC8313 in an application where it is the master controller to a few slave devices.  Whenever the 8313 pulls either the SDA or SCL line low, we see excessive undershoot of up to -1V and causes communication problems with one of the slave devices.  We currently have 2K pull-ups since one of the devices needs the faster 400Khz bus speed.  Even if we increase the pull-up size (5-6K) we still get an unacceptable amount of undershoot.  Putting in series resistors at the input of the MPC8313 is not an option since we do not want to re-spin the board.   I'm not seeing any current control options for the I2C GPIO pins.  Does anyone have any suggestions?