The VMK180 board uses a Standard Microsystems Corporation USB3320 USB 2.0 ULPI transceiver (U99) to support a USB 2.0 type-A connector (J308). A USB cable is supplied in the VMK180 evaluation kit (standard-A connector to host computer, USB 2.0 A connector to VMK180 board connector J308). The USB3320 is a high-speed USB 2.0 PHY supporting the UTMI+ low pin interface (ULPI) interface standard. The ULPI standard defines the interface between the USB controller IP and the PHY device, which drives the physical USB bus. Using the ULPI standard reduces the interface pin count between the USB controller IP and the PHY device.
The USB3320 is clocked by a 24 MHz crystal (X8). See the Standard Microsystems Corporation (SMSC) USB3320 data sheet for clocking mode details. The interface to the USB3320 PHY is implemented through the IP in the XCVM1802 device PS.
The USB3320 ULPI transceiver circuit has a Micrel MIC2544 high-side programmable current limit switch (U100). This switch has an open-drain output fault flag on pin 2, which turns on red LED DS37 if over current or thermal shutdown conditions are detected. DS37 is located just above the U125 system controller component (callout 48 in the figure in Board Component Location).
The detailed adaptive SoC connections for the feature described in this section are documented in the VMK180 board XDC file, referenced in Xilinx Design Constraints.