Sierra Wireless AirPrime SL808 Series Product Technical Specification & Customer Design Manuallines page 53

Table 4-21: MIC input electrical characteristics
Parameters
Internal biasing
DC characteristics
AC characteristics
200 Hz<F<4 kHz
Working voltage
(MIC1_P-MIC1_N)
Maximum rating
voltage (MIC1_P
or MIC1_N)
a. Input voltage depends on the input micro gain set by AT command. Refer to [3] AirPrime MC8xxx Embedded Modules
Extended AT Command Reference
b. Value in dB. To toggle it to index value, refer to [3] AirPrime MC8xxx Embedded Modules Extended AT Command Refer-
ence.
c. Value is obtained with digital gain=0, for frequency=1 kHz.
d. Because MIC1_P is internally biased, a coupling capacitor must be used to connect an audio signal provided by an
active generator. Only a passive microphone can be directly connected to the MIC1_P and MIC1_N inputs.
Rev 1 Dec.10 Proprietary and Confidential - Specifications subject to change
The gain of both MIC inputs are internally adjusted and can be tuned using AT
commands. For more information on AT commands, refer to [3] AirPrime MC8xxx
Embedded Modules Extended AT Command Reference.
4.10.2.1 MIC microphone input
The microphone input has the following features:
• Default mode—Differential. Can also be configured in single-ended mode.
• Includes biasing for electret microphone, which can be directly connected to
the input.
• AirPrime SL808X Embedded Module has embedded AC coupling.
• For electrical characteristics, see
DC equivalent circuit
MIC1_P R
MIC1_N R
Figure 4-3: MIC equivalent circuits
Parameter
MIC1_P
Output current
R2
Z2 MIC1_P (MIC1_N = Open)
Z2 MIC1_N (MIC1_P = Open)
Z2 MIC1_P (MIC1_N=GND)
Z2 MIC1_N (MIC1_P=GND)
Impedance between MIC1_P
and MIC1_N
a b
AT+VGT =3500
a b
AT+VGT =2000
a b
AT+VGT =700
Positive
Negative
Table 4-21.
MIC1_P
MIC+
MIC1_N
GND
Minimum Typical
2 2.1
0.5
1650 1900
1.1 1.3
0.9 1.1
1.3 1.6
13.8
77.5
346
-0.9
AC equivalent circuit
Z2
Z2
GND
Maximum Unit
2.2 V
1.5 mA

2150

1.6 k
1.4
2
c
18.6 mVrms
c
104
c
466
d
+7.35 V
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