Specifications

WM_PRJ_Q2400_PTS_001 - 003
6th November 2002
confidential ©
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2.11.3.2 Microphone 1 Inputs
The MIC1 inputs are differential and do not include internal bias. To use these
inputs with an electret microphone, bias has to be generated outside the
WISMO Quik Q2403 Series module according to the characteristic of this
electret microphone. These inputs are the standard ones used for an external
headset or a handsfree kit.
AC coupling is already embedded in the module.
2.11.3.2.1 Differential connection
Impedance of the microphone input in differential mode:
•
Module ON: R
in
= 10K
Ω
+/-10%
•
Module OFF: R
in
>1M
Ω
+/-10%
Typical implementation:
L1
L2
C1 C2
C4
C3
MIC1P
MIC1N
VCC
C5
R1
R2
R3
R4
Figure 6 : MIC1 inputs (differential connection)
R1 = R4 = from 100 to 330
Ω
R2 = R3 = usually between 1K
Ω
and 3.3K
Ω
as per the microphone
characteristics
C1 = 10pF to 33pF
C2 = C3 = C4 = 47pF to 100pF
C5 = 47µF
L1 = L2 = 100nH
R1 and R4 are used as a voltage supply filter with C5.
C1 has to be the nearest possible to the microphone. Microphone
manufacturers provide this capacitor directly soldered on the microphone.
C2 has to be very close to the WISMO Quik Q2403 Series connector.
L1, L2, C3 and C4 has to be put near the WISMO Quik Q2403 Series 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.