Nokia Mobile Phones NSE-5 Series, Service Manual, Page: 44 / 327

PAMS
Technical Documentation
NSE–5
System Module
Page 2 – 30
Issue 1 07/99
Audio Control
The audio control and processing is taken care by the COBBA–GJP,
which contains the audio and RF codecs, and the MAD2, which contains
the MCU, ASIC and DSP blocks handling and processing the audio
signals.
System
Connector
Pre
& LP
D
MIC1
LP
A
D
MIC3
MIC2
EAR
HF
AuxOut
MCU
Buzzer
DSP
Buzzer
Driver
Circuit
MAD
Bias +
EMI
XMIC
XEAR
HFCM
SGND
EMI+ACC
Interf.
EMI
Preamp
Multipl. Premult.
Amp
Multipl.
COBBA
A
EMI
Slide
Display
Figure 12. Audio Control
The baseband supports three microphone inputs and two earphone
outputs. The inputs can be taken from an internal microphone, a headset
microphone or from an external microphone signal source. The
microphone signals from different sources are connected to separate
inputs at the COBBA–GJP asic. Inputs for the microphone signals are
differential type.
The MIC1 inputs are used for a headset microphone that can be
connected directly to the system connector. The internal microphone is
connected to MIC2 inputs and an external pre–amplified microphone
(handset/handfree) signal is connected to the MIC3 inputs. In COBBA
there are also three audio signal outputs of which dual ended EAR lines
are used for internal earpiece and HF line for accessory audio output. The
third audio output AUXOUT is used only for bias supply to the headset
microphone. As a difference to DCT2 generation the SGND ( = HFCM at
COBBA) does not supply audio signal (only common mode). Therefore
there are no electrical loopback echo from downlink to uplink.