ULPI interface

Some microcontrollers and FPGA does not integrate USB PHY internally. This meant USB, D+ and D- signals are not output form them. To achieve USB communication with these chips, ULPI (UTMI+Low pin interface) interface shall be provided. UTMI stands for Universal Transceiver Macro cell interface. ULPI is designed to replace UTMI interface (which uses ~22 pins) with a much smaller 8-pin bus.

Below is the ULPI pin out:

• ULPI has total of 12-pins
• Operates up to a clock speed of 60 MHz
• Enables USB 2.0 High-Speed (480 Mbps) with lower pin count

Below are some of the USB PHY chips which connected to FPGA/Microcontroller using the ULPI interface.

Here is a block diagram of the USB PHY interface (STULPI01A, STULPI01B) with controller.