WA_DEV_FEX20_UGD_002
Rev 002
April 26, 2010
44
Fastrack Xtend User Guide
Interfaces
Impedance between
MIC2P and MIC2N
1.3
1.6
2
Working voltage
( MIC2P-MIC2N)
AT+VGT*=3500dB
13.8
mVrms
AT+VGT*=2000dB
77.5
AT+VGT*=700dB
346
Maximum rating voltage
(MIC2P or MIC2N)
Positive
+7.35**
V
Negative
-0.9
*
The input voltage depends of the input micro gain set by AT command. Refer to document [7] Firmware 7.4a
**
Because MIC2P is internally biased, it is necessary to use a coupling capacitor to connect an audio signal
provided by an active generator. Only a passive microphone can be directly connected to the MIC2P and MIC2N inputs.
Refer to the following table for the list of recommended microphone characteristics.
Table 16: Recommended Microphone Characteristics
Feature
Values
Type
Electret 2V/0.5 mA
Impedance
Z = 2k
Sensitivity
-40dB to -50dB
SNR
> 50dB
Frequency response
Compatible with GSM specifications
5.1.2.4.2.
Speaker
The speaker outputs are connected in differential mode to reject common mode noise and TDMA
noise.
Speaker outputs are connected to internal push-pull amplifiers and may be loaded down with
components between 32 ~ 150
and up to 1nF. These outputs may be directly connected to a
speaker.
The output power may be adjusted by 2dB steps. The gain of the speaker outputs is internally
adjusted and may be tuned using the
AT+VGR
command. Furthermore, the digital gain can be
adjusted using
AT+WDGR
. Refer to document [7] Firmware 7.4a
Wireless Software Suite 2.31)/Firmware 7.4 AT Commands Manual (Sierra Wireless Software Suite
2.30) for more information about these AT commands.
The following table shows the pin assignments of the speaker outputs.
Table 17: Speaker Outputs Pin Description
(Sub D
15-pin)
Pin #
Signal
I/O
I/O Type
Description
10
CSPK2P
O
Analog
Speaker positive output
15
CSPK2N
O
Analog
Speaker negative output
