Audio Codec '97

AC ‘97 Component Specification Revision 2.3 Rev 1.0
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modem Codec can use the low-to-high transition on RESET# as a reliable indication that power has been
reestablished on the AC-link, and that an actual resume reset has occurred.
An AC ‘97 2.3 Controller/Codec arrangement deployed as a PCI add-in card could have its AC-link RESET# signal
follow the PCIRST# signal directly since PCIRST# will always be asserted whenever the system is sleeping in S3,
S4 or S5.
7.5 Power Distribution
The AC ‘97 Revision 1.03 architecture was intended to enable low cost, yet high performance audio Codecs by
establishing a standard split of the digital and analog portions of the audio subsystem. AC ‘97 Revision 2.0 brought
low cost, and flexible integration of a modem Codec to the AC-link as well. The AC ‘97 Revision 2.2 architectural
enhancements and clarifications are intended to help in merging the two subsystems with the ACPI-based Instantly
Available PC power management initiative.
The desired result in applying Instantly Available PC technology to the audio and modem subsystems is to maintain
AC ‘97 ’s high audio quality, while not compromising an AC-link modem Codec’s ability to wake the system from
a very low power, deep sleep state. To meet these objectives audio designers must have the ability to derive locally,
a tightly regulated Vref supply for the Codec’s DACs and ADCs. At the same time the modem Codec must have
auxiliary power available to them so that they may alert the system of a ringing phone even from an ACPI S3, or S4
sleep state where 95% of all PC power is shut off.
For more details on Instantly Available PC Power Management terminology and specifications, refer to the Instantly
Available PC System Power Delivery Requirements and Recommendations Specification, which can be downloaded
from:
http://developer.intel.com/design/power/supply98.htm
The following subsections detail Instantly Available PC power distribution requirements for what is expected to be
the three predominant AC ‘97 2.2 configurations.
7.5.1 MC ‘97 (Primary) Implementations
In support of an Instantly Available PC’s “Off-yet Communicating” capabilities, modem Codecs must be capable of
waking the system from a sleep state wherein the main power rails have been shut off. This implies the usage of
auxiliary power.
Table 49 illustrates, all AC-link signals driven from the modem Codec, as well as all modem Codec circuitry (both
digital and analog) must be powered by an auxiliary 3.3 V supply (3.3 Vdual).