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VIPER Technical Manual Detailed hardware description
© 2007 Eurotech Ltd Issue E 56
Audio
A National Semiconductor LM4549 AC’97 audio CODEC is used to support the audio
features of the VIPER. Audio inputs supported by the LM4549 are stereo line in and a
mono microphone input.
The LM4549 provides a stereo line out that can also be amplified by a National
Semiconductor LM4880 250mW per channel power amplifier, suitable for driving an 8Ω
load. The LM4549 AC’97 codec may be turned off if it is not required. See the section
357HAudio power management, page 358H84, for details.
Connection to the VIPER audio features is via header PL6. See the table below for pin
assignments and the section
359HPL6 – Audio connector, page 360H91, for connector and
mating connector details.
Function Pin Signal
Signal levels (max) Frequency
response (Hz)
10 MIC input
Microphone
9
7
MIC voltage reference output
Audio ground reference.
1Vrms 20 – 20k
1 Line input left
5 Line input right
Line in
3 Audio ground reference
1Vrms 20 – 20k
2 Line output left
6 Line output right
Line out
4 Audio ground reference
1Vrms 20 – 20k
8 Amp output left
11 Amp output right
Amp out
12 Audio ground reference
1.79V peak ,
1.26Vrms
(8Ω load) 223mW
20 – 20k
The left and right amp output signals are not AC coupled, these signals must be
AC coupled with 100uF capacitors externally.
V
L