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PCA9306 without low reference voltage in the board

Question asked by Hernán Contigiani on Oct 8, 2016
Latest reply on Dec 21, 2016 by Hernán Contigiani

Hi,

 First of all thanks for your support. I have two differents boards connected by I2C, a single board computer (SBC) connected to a driver led in another board. The SBC board has a 3.3V I2C and the driver led a 5V I2C, so I am planning to use the PCA9306.
  The problem is that the SBC is already design and I cant take 3.3V from there. The connector only have I2C_SCK, I2C_SDA and GND lines to connect with the driver led board. My only chance is to include the PCA9306 in the driver led board but I dont have 3.3V reference for VREF1. The SBC already has pull-up 4.7K inside the board.
  I understand that VREF1 is only a voltage reference that may be closer to the voltage supply of the SBC, so I think that I could connect VREF1 to 5V via a voltage divider to reach the 3.3V (LDO is too expensive for this purpose)
  Based on your experience, could you be so kind to take a look to the following schematic? Is there any issue to use VREF1 based on VREF2?
PCA9306 topology
Thanks a lot, Hernan

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