Baseband Design
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This document is the sole and exclusive property of WAVECOM. Not to be distributed or divulged
without prior written agreement.
WM_PRJ_Q24NG_PTS_002-001 June
2006
B/ Single-ended connection
Typical implementation:
L1
C1
C2
MIC1P
MIC1N
V
AUDIO
C4
R1
R2
L2
C3
C5
Figure 15: MIC1 inputs (single-ended connection)
Note: V
AUDIO
must be very “clean” in single-ended connection (for
example, VCC plus filter cell such as RC or LC).
R1 = from 100
Ω
to 330
Ω
.
R2 = usually between 1 k
Ω
and 3.3 k
Ω
as per the V
AUDIO
voltage level and
the microphone characteristics.
C1 = 10 pF to 33 pF.
C2 = C3 = C5 = 47 pF to 100 pF.
C4 = 47 µF.
L1 = L2 = 100 nH.
R1 is used as a voltage supply filter with C4.
C5 has to be as close as possible to the microphone. Microphone
manufacturers provide this capacitor directly soldered on the microphone.
C1, C2, C3 have to be very close to the Q24NG connector.
L1, and L2 has to be placed near the Q24NG connector and can be
removed according to their environment (ground plane, shielding ...etc).
The best way is to plan all the components and to remove those which are
not necessary to filter out the TDMA noise on the audio path.
