Technical information

Audio Interface
28 G24-L Module Hardware Description November 15, 2008
Figure 2-16 shows the microphone circuit and Table 2-7 gives the microphone specifications.
Figure 2-16: Headset Microphone Circuit
Important: The headset microphone circuit design depends on the type of microphone device.
A series capacitor is required in case a passive microphone is used, or the
application provides a separate bias voltage to an active microphone circuit.
The internal G24-L biasing circuit may also be used with an active microphone,
which corresponds to the headset microphone port specifications.
Speaker Port
The analog speaker port is the G24-L power-up default active output for voice calls and DTMF
tones. It is located at pins 67 and 69 on the G24-L interface connector, named SPKR_N and
SPKR_P respectively.
It is designed as a differential output with 32Ω impedance, but may also be used as a single-ended
output referenced to the G24-L analog ground.
The speaker output is used for both the handset and the headset audio paths.
Table 2-7:
Headset Microphone Port Specifications
Parameter Conditions Min Typ Max Unit
Input Voltage No load 2.0 V
pp
Gain Programmable by
+MMICG
031dB
AC Input
Impedance
Freq=1Khz 1 kΩ
Bias voltage R
BIAS
= 2.0 kΩ
I
BIAS
< 1 mA
2.0 V
Bias Current 1 mA