Electronic – What does an MCU need to be capable of USB 3.0 communication


USB 3.0 has been around for quite some time, since it was released in 2008. But you don't see any simple microcontrollers with an internal peripheral that can do USB 3.0.

The Atmega32u4, a simple 8-bit AVR, has an embedded USB2.0 phy inside and only runs at 16MHz, as such it is obviously too slow to do USB3.0. Although there are Cortex-M controllers running at over 200MHz that don't have a USB3.0 peripheral! At this point, I feel like the clock for the MCU no longer matters. The lowest end processor I can find that does USB 3.0 is TIs Keystone MPU with an ARM-A15

Is it just taking a considerable amount of time to create the IP for lower end MCUs or does it require a clock generation (or some other) unit that isn't worth the cost to develop it for cheaper MCUs?

Best Answer

USB 3.0 PHY (physical, electrical) layer achieves the 5Gbit/s transmission rate utilizing high speed differential signaling (CML), same as PCI Express. Implementation of this physical layer on chip requires a transceiver, and a SERDES (serializer, deserializer) at the minimum, in addition to the MAC (media access control) layer requirements. These blocks would probably require additional clock generation and signal conditioning circuitry (equalizers on the lines to reduce bit error rates). Putting all this circuitry in your chip has two primary costs, silicon area and power.

Even if we assume if the power consumption is irrelevant, as you can turn the whole thing off if you're not using it, shipping a MCU with a USB 3.0 PHY would probably increase the silicon area enough to increase the costs drastically.