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Workstation 5 Field Service Guide
Workstation 5 System Board Technical Descriptions
USB Interface
USB Hub
The USB2 port from the Companion Device is fed to
USBDP0
, the upstream
port of U21, an SMSC 2503 3-port hub. The device is fully compatible with
the USB 2.0 specification. It adds three additional USB Ports, assigned to the
following connectors.
The
USBDP1
port is fed to IO port connector CN6B.
The
USBDP2
and
USBDP3
ports are fed to IO Port Connector CN8.
CN8 Port Power
U16, an LM3526 Dual Port USB Power Switch handles the power and
current-limit requirements for dual USB connector CN8. 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.
