Workstation 5 Field Service Guide
2-37
Workstation 5 System Board Technical Descriptions
System Board Power Distribution
VCORE
VCORE
is the primary LX800 Processor supply voltage and is active in the
WORKING domain.
System Boards up to Revision E use the ALXC800EETJCVD variant of
the LX800 that requires a
VCORE
of 1.20V. R282 in the VCORE
Regulator Circuit is 511
Ω.
System Boards Revision F or later use the ALXD800EEXJCVD C3 variant
of the LX800 that requires a
VCORE
of 1.25V. R282 in the VCORE
Regulator Circuit is 562
Ω
.
Working, Standby and System Reset
When power is applied to the Companion Device from a cold start (e.g., the
AC power cable is connected to the unit) the external sub-system must assert
RESET_STAND#
as Standby power is applied, followed by
RESET_WORK#
as Working power is applied.
RESET_STAND#
(Reset the Standby Power Domain) is provided by U48, a
LP3470 Tiny Power On Reset Device located on Sheet 8. This device is
designed to monitor a specific power supply voltage (in this case
VCC5SB
)
and assert
RESET_STB#
when the input voltage falls below the
pre-programmed threshold of 3.08V. The reset remains asserted for an interval
determined by C496. When
VCC5SB
rises above a threshold of 3.08V,
RST_STB#
remains asserted for a period programmed by C496, then
de-asserts.
RESET_WORK#
(Reset the Working Power Domain) is generated by U47, a
second LP3470 Tiny Power On Device located on Sheet 26. U47 is also
programmed to activate at 3.08V, but the input is tied to
VCC3SB
. The reset
remains asserted for an interval determined by C489. When
VCC3SB
rises
above a threshold of 3.08V,
RST_WORK#
remains asserted for a period
programmed by C489, then de-asserts.
In response to the
RESET_WORK#
and
RESET_STANDBY#
inputs, the
Companion Device asserts
RESET_OUT
, referred to on the schematic as
PCI_RST#
.
PCI_RST#
is the master system board reset, fed to all major
components including the LX800 processor, BIOS Chip, Ethernet Controller,
Super IO #1 and 2, Audio Codec, and Mini-PCI Connector CN11.
All three reset signals are required to start the system board processor.
