Q2426B
| Model | Q2426B |
| Description | SELF CONTAINED E GSM/GPRS 900/1800 OR 850/1900 BI BAND MODULE |
| PDF file | Total 81 pages (File size: 909K) |
| Chip Manufacturer | ETC |
WM_PRJ_Q2400_PTS_002 - 002
24th January 2003
2.12.1.3 Auxiliary Microphone Inputs (MIC1)
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 Q24x6 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.
2.12.1.3.1
Differential connection
Impedance of the microphone input in differential mode :
•
•
Module ON : R
in
= 10KΩ +/-10%
Module OFF : R
in
>1MΩ +/-10%
Typical implementation:
VCC
R1
C3
R2
L1
MIC1P
C5
C1
L2
MIC1N
R3
C4
C2
R4
Figure 4 : MIC1 inputs (differential connection)
R1 = R4 = from 100 to 330Ω
R2 = R3 = usually between 1KΩ and 3.3KΩ 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 Q24x6 Series connector.
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