ICs for Telephone
s
Pin Descriptions
1. Hand Set Communications Block (HSu)
[ Transmitter System]
Microphone amplifier
Input : pin3 (minus input), Output : Pin38 (collector out-
put)
The gain and frequency characteristics are determined by
the external resistors R19 (6.8kΩ)and R20 (43kΩ), and
capacitors C24 (0.068µF)and C25 (1,000pF).
R21 (2.2kΩ)is a resistor for the power supply for ECM.
AN6426NK
33
37
38
[Receiver System]
Receiver preamplifier
Input : Pin11(minus input), Output : Pin10 (collector out-
put)
The gain and frequency characteristics are determined by
the external resistors R5 (1kΩ)and R4 (22kΩ), and capac-
itors C8 (0.1µF)and C7 (3,300pF)
Transmitter selector switch
Input : Pin39 (speech), Pin40 (MF, holding tone)
The switch changes over transmitter input for hand set
communications, transmitter input for hand-free communi-
cations, and MF (Multi Frequency) input. The input impe-
dance at the Pin39 is 3.9kΩ and DC is VR (Pin34)
C33 (4.7µF) is a DC preventive capacitor. R22 (33kΩ) is
to adjust the input to the log amplifier. which is to detect
the transmission level. It attenuates the amplifier input to
3.9/(3.9+R22 (33kΩ)
The input impedance at the Pin40 is 3.35kΩ and DC is VR.
C34 is input through 10µF.
11
10
39
Receiver selector switch
Input : Pin10, Pin40
The switch changes over receiver input for hand set com-
munications and MF input.
Receiver automatic pad
Control : Pin33
Common with transmitter automatic pad
Receiver buffer amplifier
Output : Pin9
Outputs a receiver signal for hand-free communications at
low inpedance.
40
9
Transmitter automatic pad
Control : Pin33
Varies the transmitter/receiver gain by the value of the
current supplied to the IC. A variable point can be
moved by R18 (100kΩ). Increasing R18 causes AP to
start operation at a higher line current.
5
PANASONIC [ PANASONIC SEMICONDUCTOR ]
