Preliminary
19
22
20
21
23
M1
M2
M4
M3
VOL
AI
AI
D/AI
AS2520/21/20B/21B
Microphone Inputs
Differential inputs for handset microphone (electret).
Handsfree Microphone Inputs
These are the input pins for the handsfree microphone (electret).
Volume Control Input
Volume control for the receive signal.
AS2520: Digital control with +/– keys or from µC;
AS2521: Analogue dc control with potentiometer.
Supply Source Control Output
This N-channel open drain output controls the external high power source
transistor for supplying (V
PP
) the loudspeaker amplifier in off-hook
loudhearing/handsfree mode.
Current Shunt Control Output
This N-channel open drain output controls the external high power shunt
transistor for the modulation of the line voltage and for shorting the line
during make period of pulse dialling.
Negative Power Supply
Line Input
This input is used for power extraction and line current sensing.
Receive Input
This is the input for the receive signal.
AI:
AO:
AI/O:
Analogue Input
Analogue Output
Analogue Input/output
24
SS
AO
25
CS
AO
26
27
28
DI:
DO:
DI/O:
V
SS
LI
RI
Supply
AI/O
AI
Digital Input
Digital Output
Digital Input/Output
Operating Modes
I/O Pins
MODE
Idle (on-hook)
Ringing
POT
POT/pulse dialling
POT/DTMF dialling
Handsfree
Handsfree/pulse dial
Handsfree/DTMF dial
Loudhearing
Loudhearing/pulse dial
Loudhearing/DTMF dial
TAM without LSP
TAM with LSP
Melody feedback
Test mode 1
Test mode 2
HS
0
0
1
1
1
0
0
0
1
1
1
1
1
0
0
0
Digital Inputs
LE
0
0
0
0
0
1
1
1
1
1
1
0
1
1
0
0
PD
0
1
0
1
0
0
1
0
0
1
0
1
1
1
0
1
MT
0
0
0
1
1
0
1
1
0
1
1
0
0
0
1
1
Table 1: Operating Modes
Rev. 5.1
Page 3
May 1999
Tone Input
TI
Not connected
PDM signal to LO (DI)
Not connected
Not connected
DTMF to LI and RO (AI)
Not connected
Not connected
DTMF to LI and RO (AI)
Not connected
Not connected
DTMF to LI and RO (AI)
Signal to LI (AI)
Signal to LI (AI)
PDM signal to LO (DI)
CM
Low
SW
Low
Low
Low
Low
Low
Low
Low
Low
Low
Low
Low
Low
LI
-
-
‘M1/M2’
V
BE
‘TI’
‘M3/M4’
V
BE
‘TI’
‘M1/M2’
V
BE
‘TI’
‘RI/STB’
‘RI/STB’
‘RI/STB’
‘LSI’
‘LSI’
‘RI/STB’
Outputs
RO
PD
-
‘RI/STB’
-
‘TI’
‘RI/STB’
LO
PD
‘TI’
-
-
-
‘LSI’
-
‘LSI’
‘LSI’
Reserved for testing
Reserved for testing
AMSCO [ AUSTRIAMICROSYSTEMS AG ]
