Specifications

WM_PRJ_Q2400_PTS_001 - 003
6th November 2002
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2.11.1 Common microphone inputs characteristics
The connection can be either differential or single-ended but using a differential
connection in order to reject common mode noise and TDMA noise is strongly
recommended. When using a single-ended connection, be sure to have a very
good ground plane, a very good filtering as well as shielding in order to avoid
any disturbance on the audio path.
Internal audio filter characteristics
Frequency Gain
0-150 Hz < -22dB
150-180 Hz < -11dB
180-200 Hz < -3dB
200-3700 Hz 0dB
>4000 Hz < -60dB
The gain of MIC inputs is internally adjusted and can be tuned from 30dB to
51dB using an AT command.
Microphone gain vs Max input voltage
Transmit Gain (dB) Max Vin (mVrms) AT+VGT(*)
30 43.80 0 to 31
33 31.01 32 to 63
36 21.95 64 to 95
39 15.54 96 to 127
42 11 128 to 159
45 7.79 160 to 191
48 5.51 192 to 223
51 3.9 224 to 255
(*) control of the transmit gain by AT commands (for WISMO Quik Q2403
Series driven by AT commands)
Recommended characteristics for the microphone:
•
2V – 0.5mA
•
2 KOhms
•
Sensitivity -40 to –50dB
•
SNR > 50dB
•
Frequency response compatible with the GSM specifications
For possible references, see chapter Connectors and peripheral devices
references, §4.4.