User's Manual
PCS3_HD_v01.000-03
Confidential / Preliminary
Page 41 of 101
2013-10-21
PCS3 Hardware Interface Description
3.8 Analog Audio Interface
3.8.1
Microphone Inputs and Supply
The differential microphone inputs MICP and MICN present variable impedances depending
on the gain. The microphone inputs must be decoupled by capacitors Ck (typical 1µF). The in-
put stage uses a differential operational amplifier circuit with programmable resistors in the in-
put and the feedback path. The detailed structure of this stage and the following uplink path is
shown in Figure 11. The input can be controlled by the AT command AT^SNFI. Command pa-
rameters with their effect are mentioned in the figure and marked in <red>. More information
about audio AT commands can be found in Section 6.7 and [1].
Module
Rs
VMIC
Ck
MICN
<micAmp1> 0dBm
or 24dBm
VMIC
AGND
-
A
PCM
X
Ck
MICP
Rs
AGND
AGND
D
<micTxVol>
GND
GND Line leading burst current
GND
V Noise
Application GND
Connection Resistance
Figure 11: Structure of Audio Input and Supply