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

The microphone input includes all the necessary circuitry to support a direct connection to a
headset microphone device. It incorporates an internal bias voltage of 1.8V through a 2.2kΩ
resistor, and has an impedance of 1kΩ.
Figure 2-16
Figure 2-16: Headset Microphone Circuit
Important:

Speaker Port

The analog speaker port is the C24 power-up default active output for voice calls and DTMF
tones. It is located at pins 67 and 69 on the C24 interface connector, named SPKR_N and
SPKR_P respectively.
December 15, 2008
shows the microphone circuit and
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 C24 biasing circuit may also be used with an active microphone, which
corresponds to the headset microphone port specifications.
Table 2-7: Headset 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
Chapter 2: Hardware Interface Description
Table 2-7 gives the microphone specifications.
Min Typ Max
1.6
9 36
1
1.8
1
Unit
V
pp
dB
kΩ
V
mA
27