n Overview
The AN6425K is a high-function speech network IC with
speaker amplifier. It incorporates a transmitter-system non-lin-
ear circuit, receiver digital VRs, etc. and is suitable for realiz-
ing the multifunctional telephone sets.
n Features
• Speech network IC for the multifunctional telephone sets
• Capable of interfacing with the light-weight small receivers
and ECM transmitters
• Built-in 2V REG constant voltage source (2V typ) for ECM
• Built-in non-linear circuits in the transmitter and receiver
systems in order to eliminate ambient noises
• Built-in speaker amplifier and capable of driving with a main
wire current
• Built-in hold-tone amplifier, key-in-tone amplifier, and
DTMF transmitter, and capable of setting the mode with the
control pins
• Automatic gain control (automatic pad function) according to
a circuit curret
• Built-in tertiary active filter circuit and capable of sending a
DTMF circuit with much higher harmonic at a low distortion
factor
• Built-in single touch receiver volume-up function (about
6dB)
AN6425K
Speech Network Circuit
Unit : mm
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
26.7
–
0.3
0.5
–
0.1
3 to 15˚
8.4– 0.3
0.9
–
0.25
1.778
4.8– 0.25
28-pin Shrunk DIL Plastic Package (SDIP028-P-0400B)
3.05– 0.25
10.16– 0.25
0.3
+
0.1
– 0.05
1.05– 0.25
1 2 3 4 5 6 7 8 9 10 11 12 13 14
28 27 26 25 24 23 22 21 20 19 18 17 16 15
TT
in
HT
KT
40kΩ
80kΩ
MIC
in
Filter
Amp.
SEND
Amp
MUTE

Logic
INV
NAND
DVR
4kΩ
65kΩ
30kΩ
2kΩ2kΩ
1V
30kΩ
CLASS B
BTL
CLASS A
Push pull
+
–
–
+
–
+
REC
in
D6dB
D5dB
D3dB
D3dB
D12
dB
2V
1V
GND
VL
VL
2V REG
1V REFF
Battery
Selector
REC
DRIVER
REC
DRIVER
SP
Amp.
n Block Diagram