TCA9555: Asking for the TCA9555 design suggestion

SHH,

The note on the schematic is correct that these I/O ports are 5V-tolerant. An input V_IH of 5 V will be recognized as a logic high even with a V_CC of 3.3 V.

However, I noticed that a few of the net names for certain outputs indicated that they connect to 5V I/O pins downstream (e.g. 5V_OT2211_EN and 5V_F75501_EN). Note that the high-level output voltage V_OH for a P-port output is dependent upon V_CC.

Since this TCA9555 appears to be powered with a V_CC = 3.3 V, it is important to ensure that the resulting output voltage V_OH of these pins meets the high-level requirement of the downstream devices. I'd expect V_OH(min) to be somewhere around 2.6 V to 2.8 V.

Best,

Danny

SHH,

I looked over the parts of the schematic and circuitry directly associated with TCA9555 (U4250), and nothing stood out as wrong for me, assuming your I2C lines are properly open-drain (rather than push-pull), and assuming your bus capacitance is appropriate. More info on calculating pull-up resistor values can be found here.

Best,

Danny