– 5–10 –
GSM Processor
(AD6525)
ADC/DAC
VoiceBand
&
BaseBand
Codec.
(AD6521)
MIC
Speaker
GPIO5
A,V,B
serial Port
LDO 3.0V
Receiver
Meledy IC
MA1
Control /Data
Interface
VOUTNOR P/N
Phone
Jack
VOUTAUX P/N
Audio
AMP
Buzzer(L_SPK Mode)
VINNOR P/N
VINAUX P/N
HPOUT
Figure 5.9. Audio system block diagram
AD6521 is a Voiceband Baseband Codec (VBC) that combines, onto a single chip, all A/D and D/A converters that are
necessary to build a complete GSM, DCS1800, and PCS1900 mobile radio. It has two differential output port, two
differential input ports, and a buzzer output. Voiceband normal output is used in normal receiver mode.
Voiceband auxiliary output is used in earpiece receiver mode. Buzzer output signal via a meledy IC is used in loud-speak
mode. About input, voiceband normal input is used to microphone and the auxiliary input is design for earpiece microphone.
5.3.1. Voiceband Baseband Codec
Chipset ADI AD6521
Package 64-Ball LFBGA
Feature
■
Complete Analog/Digital Interface for Voiceband Input/Output-Signals; Baseband Input/Output-Signals;
Auxiliary/Control-Signals
■
Baseband Codec
Supports Multi-slot Operation
Differential I and Q Inputs/Outputs
On-Chip GMSK Modulator for GSM
Two 10-Bit D/A Converters
10-Bit RAMP D/A Converter
On-Chip RAMP-RAM
Two High Resolution A/D Converters
On-Chip FIR-Filter
■
Voiceband Codec
Complete Linear Coded Codec
Two Channel 16-Bit A/D Converter with Filter
Complete Microphone Interface
Two Channel 16-Bit D/A Converter with Filter
Complete Speaker Drive Capability
Programmable Gain on Input and Output
Multi-Standard Sample Rate Conversion
■
Auxiliary Section
13-Bit AFC D/A Converter
10-Bit Current DAC
Six Channel 10-Bit A/D-Converter
5.3. Audio System