Workstation 5 Field Service Guide
2-17
Workstation 5 System Board Technical Descriptions
USB Interface
Companion Device
U41, the CS5536 companion device supplies four USB ports. One port, USB0
is fed to IO panel connector CN6A.
The USB1 output drives J9, the USB Flash Drive Connector.
USB Flash Drive Power Control
In the Windows Embedded CE 6.0 and current WEPOS configuration, the
USB Flash Drive is the primary boot device. A pre-boot POST test ensures
the device is installed.
However, to provide the flexibility of booting from the CF Card, a BIOS
field is available that removes power from J9, the USB Flash Drive
connector.
A GPIO signal from U8, Super IO #1 called
UDOC_ON
is controlled by
the ‘Boot Test Image’ field of the Special Configuration screen of BIOS
Setup.
UDOC_ON
drives a switch consisting of Q6 and Q8. The default
setting of ‘Normal’ sets
UDOC_ON
high, enabling the switch and
providing
VCC5_UDOC
to power the USB Flash Drive.
When the Boot Test image field is set to ‘Alternate,’
UDOC_ON
goes low,
and turns off switch, cutting power to the USB Flash Drive socket.
Using the ‘Reset BIOS to WINCE or WINXPE defaults’ automatically sets
the Boot Test Image field to ‘Normal,’ to allow booting from the USB
Flash Drive.
The USB2 port drives the input of USB Hub U21, a device that adds three USB
ports to the System Board. See below.
The USB3 port drives J10. This is a right angle 2x5 connector positioned at the
front edge of the system board and accessed through a cut-out in the cage.
Currently the optional Integrated Finger Print Reader is connected to this port.
Future options could also use this USB Port.
CN6 Port Power
U30, an LM3526 Dual Port USB Power Switch handles the power and
current-limiting requirements of dual USB connector CN6. The device
contains a pair of P-channel MOSFETS (one for each port) with separate
enables and fault outputs. In a typical application, current flows from the
IN(put) pins through the MOSFET and OUT towards the load.
The device employes a two-stage thermal protection circuit. If the internal
temperature is greater than 150
°
C, both MOSFETs are turned off and the
fault outputs, FLAGA# and FLAGB# go active. These outputs have a 1 ms
delay to prevent false over-current reporting from the in-rush current
caused by hot plug events. Shorted switches will continue to cycle off and
on, due to the rising and falling die temperature, until the short is removed.