The VPK180 evaluation board uses a Standard Microsystems Corporation USB3320 USB 2.0 ULPI transceiver (U99) to support a USB 2.0 type-A 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 signaling. 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 XCVP1802 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.
