Audio Control - Nokia NSE–3 SERIES Service Manual

PAMS
Technical Documentation

Audio control

The audio control and processing is taken care by the COBBA–GJ, which
contains the audio and RF codecs, and the MAD2, which contains the
MCU, ASIC and DSP blocks handling and processing the audio signals. A
detailed audio specification can be found from document
Bias +
EMC Preamp
Premult.
MIC2
MICP/N
MIC1
MIC3
EMC + Acc.
Interf.
XMIC
SGND
XEAR
HFCM
Amp
AuxOut
EMC HF
EAR
The baseband supports three microphone inputs and two earphone out-
puts. The inputs can be taken from an internal microphone, a headset mi-
crophone or from an external microphone signal source. The microphone
signals from different sources are connected to separate inputs at the
COBBA–GJ asic. Inputs for the microphone signals are differential type.
The MIC1 inputs are used for a headset microphone that can be con-
nected directly to the system connector. The internal microphone is con-
nected to MIC2 inputs and an external pre–amplified microphone (hand-
set/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 au-
dio output AUXOUT is used only for bias supply to the headset micro-
phone. As a difference to DCT2 generation the SGND ( = HFCM at COB-
BA) does not supply audio signal (only common mode). Therefore there
are no electrical loopback echo from downlink to uplink.
The output for the internal earphone is a dual ended type output capable
of driving a dynamic type speaker. The output for the external accessory
and the headset is single ended with a dedicated signal ground SGND.
Input and output signal source selection and gain control is performed in-
side the COBBA–GJ asic according to control messages from the MAD2.
Keypad tones, DTMF, and other audio tones are generated and encoded
by the MAD2 and transmitted to the COBBA–GJ for decoding.
Original 11/97
COBBA
Multipl.
A
Pre
& LP
Multipl.
LP
A
System Module
MAD
DSP MCU
D
D
NSE–3
Buzzer
Driver
Circuit
Buzzer
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