Headset Microphone Port; Handset Microphone Circuit; Handset Microphone Port Specifications - Motorola 8900 - Blackberry Curve Cell Phone OEM Car Charger Developer's Manual

Audio Interface
Figure 2-15
Figure 2-15: Handset Microphone Circuit
Important:

Headset Microphone Port

The headset microphone port is designed for use with, but not limited to, a headset audio device.
It is located at pin 57 on the C24 interface connector, named HDST_MIC.
It is designed as a single-ended input and should be referenced to the C24 analog ground.
26
shows the microphone circuit and
The 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 C24 biasing circuit may also be used with an active microphone, which
corresponds to the microphone port specifications.
Table 2-6: Handset Microphone Port Specifications
Parameter Conditions
Input Voltage No load
Gain Programmable by
AT Command
AC Input Freq=1Khz
Impedance
Bias voltage R = 2.2 kΩ
BIAS
I < 1 mA
BIAS
Bias Current
C24 Module Hardware Description
Table 2-6 gives the microphone specifications.
Min Typ Max
1.6
9 36
1
1.8
1
Unit
V
pp
dB
kΩ
V
mA
December 15, 2008