Audio Linear Amplifier Lm4873 - Compaq Armada e500 Series Reference Manual

Figure 6-6 illustrates a state when all the mixers should work with the static volume
settings that are contained in their associated registers. This is used when the user could
be playing a CD (or external LINE_IN source) through the ES1921 to the speakers but
have most of the system in low-power mode. The procedure for invoking this state
follows the previous example except that the analog mixer is never shut down. The
exception is in PR5: the analog is shut down when a cold reset occurs.
PR0=1
Normal
ADCs off
PR0=0
ADC=1
Ready=1
Figure 6-6. ESS1921 Mixer Static Volume Settings
When PR3 is set to 1, ADC, DAC, Mixer, and Vref are powered down no matter what
the state of PR[3:0]. When PR3 is reset to 0, ADC, DAC, Mixer, and Vref are returned
to their previous states as determined by the state of PR[3:0]. When these subsections
are powered down (ADC, DAC, Mixer, and Vref), the ES1921 flags the appropriate
slots as invalid in Slot 0 of the audio input frame.

Audio Linear Amplifier LM4873

The LM4873 is a dual bridge-connected audio power amplifier which, when connected
to a +5V supply, will deliver 2.1W to a 4 Ohm load with less than 1.0% THD+N. In
addition, the headphone input pin allows the amplifiers to operate in single-ended mode
to drive stereo headphones. A Mux Control pin toggles between the two stereo sets of
amplifier inputs, allowing for two select-able amplifier closed-loop responses. To
simplify audio system design, the LM4873 combines dual bridge speaker amplifiers and
stereo headphone amplifiers in one chip. The LM4873 features an externally controlled,
low-power consumption shutdown mode, a stereo headphone amplifier mode, and
thermal shutdown protection. It also utilizes circuitry to reduce 'clicks and pops' during
device turn-on.
Digital I/F off
PR5=1
PR1=1
PR0 PR1
DACs off
PR1=0
DAC=1
Default
AC-Link off
PR4=1
PR4
Digital I/F off
Warm Reset
Cold Reset
Oscillator Off
Shut off
AC-Link
Audio Subsystem 6-15