TCA9617B: Under shoot issue B side Clock and data signals...

venkataseshathri sundaram said:

Part Number: TCA9617B

Hi,

We are using TCA9617B in design. 

In I2C buffer Clk & data signals timing & I2C read write OK with standard configuration.

But undershoot appears in the clock and data signal in the B side of the buffer. In A side no shoots observed.

[Bobby] B side has fall time accelerators which quickly drive the signal down to GND for a very short duration.

Kindly suggest how to reduce the undershoot in B side CLK and Data signals

[Bobby] There are two common ways to do this. The first is to place a small series resistor between B side and the pull up resistor. The second approach is to place clamping diodes from SDAB/SCLB to GND. I've recommended BAT54C in the past but it will depend on the instantaneous current that is being driven when the undershoots occur. 

//A less popular way which I don't recommend is to add bus capacitance to slow down the fall times but I2C limits the max bus cap to 550pF for fast mode plus and 400pF for fast mode so this is not ideal.

Here with i have attached circuit diagram and undershoot images for your references.

Regards,

Venkata Seshathri.S

-Bobby