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TCA9539-Q1: TCA9539-Q1 review schematic

Part Number: TCA9539-Q1

Hi, Support Team

We will use TCA9539-Q1 as below chart. have any concern?

if any suggestion, Please advise me.


Best regards,


  • Pulling the /RESET input to ground prevents the device from working.

    If the /INT output is not used, it can be left open; pulling it to ground does not make sense.

    There must be pull-up resistors on the SDA/SCL lines. I guess they are on some other part of the schematic.

    Please explain the resistors at A0/A1. In the configuration shown, they short the supply to ground.

  • Hi Lawrence, 

    I agree with Clemens on most of his comments. 

    Pulling the /RESET pin to GND prevents the device from working. /RESET is an active-low reset, and will keep the device in a reset condition as long as it is held LOW. To have proper operation, I suggest pulling this pin to VCC through pull-up resistor, and have a GPIO connected to it so there is an option to perform an external reset by driving the pin LOW. 

    If /INT is not used, you can leave this pin open. 

    Please ensure that there are pull-up resistors present on the SDA/SCL lines. I2C is an open-drain protocol. 

    P-Ports that are left as outputs can be left floating. If p-ports are configured as inputs, please tie to VCC or GND through a resistor. 

    A0/A1 connections don't make sense since two sets of 0ohm resistors are pulling to VCC and GND. Are some of these 0 ohm resistors not-populated?