SLVA787 September   2016 LM8330 , LM8335 , P82B715 , P82B96 , PCA9306 , PCA9306-Q1 , PCA9515A , PCA9515B , PCA9518 , PCA9534 , PCA9534A , PCA9535 , PCA9536 , PCA9538 , PCA9539 , PCA9543A , PCA9544A , PCA9545A , PCA9546A , PCA9548A , PCA9554 , PCA9554A , PCA9555 , PCA9557 , PCF8574 , PCF8574A , PCF8575 , PCF8575C , TCA4311A , TCA6408A , TCA6416A , TCA6418E , TCA6424A , TCA9509 , TCA9517 , TCA9517A , TCA9534 , TCA9534A , TCA9535 , TCA9538 , TCA9539 , TCA9539-Q1 , TCA9543A , TCA9544A , TCA9545A , TCA9546A , TCA9548A , TCA9554 , TCA9554A , TCA9555 , TCA9617A , TCA9617B , TCA9800 , TCA9801 , TCA9802 , TCA9803

 

  1.   Choosing the Correct I2C Device for New Designs
    1.     Trademarks
    2. 1 Introduction
    3. 2 I/O Expander Applications
      1. 2.1 RESET Pins
      2. 2.2 Internal Pullups
      3. 2.3 Address Pins
      4. 2.4 Level Shifting
    4. 3 I2C Switches
      1. 3.1 Control Register
      2. 3.2 Hot Insertion Supported
      3. 3.3 Address Pins
      4. 3.4 Level Shifting
    5. 4 I2C Buffers
      1. 4.1 Pull-Up Resistors
        1. 4.1.1 Static Voltage Offset
        2. 4.1.2 Level Shifting
    6. 5 I2C Voltage Translation

4.1.1 Static Voltage Offset

Certain devices within the I2C buffer/repeater portfolio, such as TCA9517/A and TCA9617/A/B, contain a static voltage offset. The type of buffer design on the B-side prevents these devices from being used in series with devices that use a static voltage offset. When a static voltage offset is present on the B-side of these TCA devices, they will be unable to recognize buffered low signals as a valid low and do not propagate it as a buffered low again. An example of this would include, taking two TCA9517A devices and placing them in an A-B B-A configuration. By having both B-sides in series, the design runs the risk of miscommunicating low signals as the device will be unable to recognize this and result in transmitting a high.

fig07_slva787.gifFigure 9. Example of B-B side mismatch configuration for I2C buffers