Shenzhen Coban Electronics Co. Ltd. CB900 用户手册
4.10. Analog Audio Interfaces
4.10.1.
Microphone input
The handset differential inputs MICIP and MICIN can be amplified by the differential handset
microphone amplifier. The microphone reference voltage is at 2V.
Pin Description
Electrical Characteristics
MIC Application
This section describes the two common approaches to microphone connection. Since this feature
is exposed to the environment, provision for ESD protection is recommended. Typical
characteristics of a microphone device which can be used: Impedance: ~2 kohm, sensitivity ~
40-50 dB/PA and SNR >50 dB.
Differential Ended
Differential ended connection is the recommended implementation. The following diagram shows
a proposed implementation. The capacitance values chosen may need to be optimized based on
application, for GSM related EMI, this can be from 10 pF to 47 pF for an 0402 size. If not needed,
these components may be unplaced.
Pin
Signal Name
Signal I/O
Description
13
MIC-
I
Microphone amplifier input (-ve)
14
MIC+
Microphone amplifier input (+ve)
Parameters
Conditions
Min
Type
Max
Unit
Maximum differential input range (MIC+ – MIC-)
Input 3 dBm0
-
-
0.8
Vpp
Nominal reference level (MIC+ – MIC-)
-
-
-10
-
dBm
Differential input resistance (MIC+ – MIC-)
-
-
50
-
KΩ
Amplifier gain for (MICIP-MICIN) input
Differential MIC
-
-
39
dB
Recommended MIC Impedance
-
2k
-
Ohms
Recommended MIC Sensitivity
40
-
50
dB/PA
Recommended MIC SNR
-
-
50
dB