TCA9548A-Q1: for Ethernet Phys

Hey Jon,

What is your maximum clock speed? My experience with MDIO/MDC is that it runs in the MHz range typically and our device is only rated for 400kHz so this device would likely not be suitable for this application. The pass FET architecture of this device would require strong pull up resistors to meet the stricter rise time requirements for MDIO/MDC. Using stronger pull up resistors would likely affect the VoL seen by the slave in the SMI system as well. The other problem I see is that you could potentially get the bus glicthed/stuck if you used this device above the 400kHz frequency as the state machine of this device is not suited for higher speeds and may think you are talking to it (aliasing issues).

My suggestion here may be to use a device without a state machine. Maybe a TCA9406 sitting in parallel with other TCA9406 and have GPOs (or an I2C IO expander) to disable/enable the TCA9406. TCA9406 can support up to 24MHz if driven by push/pull architectures (I believe MDC typically uses push pull and MDIO is optional for push/pull).

Let me know if this is a suitable solution or if you have further system requirements. If this device isn't suitable I can see if I can find someone else who may be able to find a product that can fit your application.

-Bobby