CALIFORNIA MICRO DEVICES
AP-211
Instantly Available PCI Card Power Management
Introduction
Today, PCs need to remain constantly connected to the outside
world, but at the same time consume minimum power. Even
when looking idle, it is still possible to receive a message
from the Internet or an incoming fax or phone call. The PC
must automatically go from sleep mode to on mode; in
other words, an Instantly Available PC (IAPC). The challenge
is to maintain a systems modem or Local Area Network
(LAN) connectivity on a desktop PC/workstation while at the
same time minimizing power consumption. These power
management features are called Wake-on-Ring (or Wake-
on-Modem), Wake-on-LAN, and Wake-on-PME (Power
Management Event).
The sleep state of an instantly available PC is called Suspend
to RAM. This is implemented by using:
split power planes in the system design, and
an auxiliary power source (VAUX) for dual mode power
distribution.
Lets focus on the PCI (Peripheral Component Interface) cards,
where California Micro Devices products have their primary
applications. By definition, all PCI add-on cards are connected
to the motherboard through the PCI bus. On the PCI
connector, several pins have been reserved in order to support
the instantly available functionality.
The main qualities/benefits of such a system are:
PME# (Power Management Event) pin (pin #A19) is
used to wake the system in response to a PCI power
management wake event such as the phone ringing.
3.3Vaux pin (pin #A14) is used to deliver the auxiliary
power of 3.3V to all the wake-up PCI cards in the system.
This power is always available to keep the card active
even when the rest of the PCI bus is without power.
Listening: available anytime to receive messages from
the outside world, and
Reacting: responding anytime to do a specific operation
(maintenanceꢀ), and
Saving energy and being silent in the idle mode.
The OnNow initiative by Microsoft defined the new
requirements for the system that affect both software and
hardware aspects of the PC: Windows operating system,
applications, device drivers, and hardware within the system.
All these elements must work together in order to provide a
fully transparent power management system. This note will
focus only on the hardware aspects.
Three different independent voltage sources are now available
on the PCI bus: 3.3VAUX, 3.3VCC, and 5VCC. In a power plane
partitioning system of an instantly available PC, the 3.3VAUX is
electrically isolated from the main PCI 3.3V rail at all times.
During normal operation, the 3.3VAUX supply remains on all
the time, while the other main supplies, 3.3VCC and 5VCC, can
be switched on and off as needed.
ACPI System Design
An instantly available PC appears to be off, yet it can snap
back to its full ready state within seconds and respond to
the phone ringing in time to service the call.
PCI Adapter Card Application
PCI Network Interface Cards (NIC) and modem cards are also
designed with split power planes. Thus, they are able to
operate in sleep mode with only the Vaux power supply and
still be able to wake-up the system.
In order to meet these requirements a recommendation, the
Advanced Configuration and Power Interface specification
(ACPI), has been defined by Intel, Microsoft, and
Toshiba.
Some NICs that operate in Wake on LAN mode get a 5V
standby through a cable that connects directly to a specific
header on the motherboard.
Instantly available motherboards include: ACPI BIOS, ACPI
chip set, and PCI slots that are compliant to the PCI-PM
specification. The Intel chip set supports the power
management features to define the ACPI sleep states and
also generates the signals to control power planes to turn
the main power supplies on and off.
Chip Set Voltage
Today, PCI card chip sets or ASICs operate at a low voltage of
3.3V. That allows much lower power consumption than with
the previous 5V modem chips. However older PCs are still
operating at 5V and do not have any 3.3VAUX supply. New
PCI cards must be compatible with these systems still in service,
and therefore must regulate on board their own 3.3V supply
from the 5V. This is made possible by using California Micro
Devices SmartOR power management products: the
CMPWR100 and CMPWR150. In addition, there is a
The implementation includes multiple power sources and
uses separate power planes in the system. Each power source
is selected depending on the required state demanded by
the system, and one of the major requirements is to switch
between power sources continuously, automatically, and
without interruption.
maximum current limitation of 375mA on the 3.3VAUX
.
All trademarks are the property of their respective holders.
©1999 California Micro Devices Corp. All rights reserved.
P/Active® is a registered trademark and SmartOR is a trademark of California Micro Devices.
C0210699A
9/99
215 Topaz Street, Milpitas, California 95035
Tel: (408) 263-3214
Fax: (408) 263-7846
www.calmicro.com
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CALMIRCO [ CALIFORNIA MICRO DEVICES CORP ]
