ADP5350 Lose I2C with LDO Discharge

Hi,

We're having a strange issue with the ADP5350.  For starters, when we turn off LDO2 / LDO3, the Voltage does not drop all the way down to 0V, but instead floats around 2V.  We figured out that putting a resistor to ground will pull it down.  Since it has an LDO Discharge feature, we tried to make use of it, however, when we turn on the LDO discharge, it pulls our I2C lines down to about 1.2V, and we lose all communication with both the ADP and all other devices on the line.

For some context, we're using the 3.3V from LDO1 for the I2C pull resistors, and we do not turn on the LDO discharge for LDO1.  The output for LDO1 continues to be 3.3V.  Our I2C pull up resistors are 4.7k.

Any help is appreciated.  Thank you!

Robert

Parents Reply
  • Hi Charly / Kevin,

    We were finally able to solve the issue, which was an error in our schematic, by sourcing a MUX with LDO2, and using LDO1 for the pull up resistors on the MUX Select pins.  Seems that a diode or FET in the MUX was creating a path for LDO1 with a voltage divider, and of course, when we turned on the 500 Ohm Discharge on LDO2 we end up with a voltage divider on the I2C lines.

    Thanks,

    RM

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