Revision 1.0 Page 11 of 25
Headset Reference Design v1.0
3.2.1.1 Headset interface
The loudspeaker(s) are dr iven differentially, and need some filtering due to the class D output amplifier of
the audio codec. Figure 7. ”Loudspeaker interface” shows a typical filter network that can be use d fo r dr iv-
ing a headset loudspeaker. The filter depends on the chosen l oudspeaker.
The microphone can be connected dir ectly to the codec input. The codec input has a 1.1 V su pply that can
power a typical headset microphone.
Figure 7. Loudspeaker interface
3.2.1.2 PC interface
The dif ferential loud speaker output from the codec mu st be connected single ended to the PC microphone
input and the PC loud sp eaker outpu t must be conn ected to the codec microphone inp ut to interface with a
PC audio port. Figur e 8. ”PC input interface” sho ws th e networks th at accommodate this. The loudspeaker
output from the PC must be level adjusted and a ne twork as sh own in Figure 9. ”PC ou tput interfac e” used.
Figure 8. PC input interface
L2
470u
C4
100p
C1
100p R1
56
R2
56
C2
4.7u C3
4.7u
L1
470u AOUTP
AOUTN
R7
4.7k
R8
4.7k
C8
2.2u
C9
2.2u
C5
10n
C7
100n
R9
22k
R4
22k
R6
22k
R5
22k
C6
10u
+
-
V-
V+
U1
LM7301
3
4
1
2
5
R3
1k
PC microphone input L2
470u
C4
100p
C1
100p R1
56
R2
56
C2
4.7u C3
4.7u
L1
470u AOUTP
AOUTN