ICs for Telephone
s
Pin Descriptions (cont.)
Receiver attenuator
Input : Pin26 (Zi=15kΩ), Output : Pin25 (emitter out-
put)
The input is of only AC component due to C18 (1µF).
At transmission time, an attenuation amount is varied with-
in a range of about 0 to –36dB by the Gilbert circuit.
The Pin25 is 15kkΩ and connected to the VB pin (1.2V).
18
19
AN6426NK
Attenuator timing control (TAC)
Control : Pin20
Controls the transmitter/receiver attenuator switching
speed with C16(2.2µF). V
20–29
≈
0V in the transmitter
mode, and V
20–29
≈
–120mV in the receiver mode.
Transmitter attenuator control (TAC)
Control : Pin21
Controls the transmitter attenuator gain with R12(22kΩ).
Receiver attenuator control (RAC)
Control : Pin23
Controls the receiver attenuator gain with R13 (22kΩ).
Transmitter/receiver attenuator control (AC)
Control : Pin22
Controls the transmitter/receiver attenuator gain with R14
(27kΩ).
26
25
20
21
22
23
[Control System]
High level ; 1 to 5V, Low level ; 0 to 0.5V
Controllable with the microcomputer.
HS
U
/SP
U
selector switch
Control : Pin30
High : HS
U
, Low : SP
U
Transmitter mute switch
Control : Pin32, High : Transmission,
Low : Mute (MF transmission)
Receiver mute switch
Control : Pin30,
High : Reception, Low : Mute (MF reception)
Speaker amplifier
Input : Pin4, Output : Pin3, AGC : Pin2
Plus input amplifier of about 34 dB and driven at 25Ω.
The input is of only AC component due to C3 (10µF). The
output drives the 25Ω speaker througt C2 (220µF). The
attack time and recovery time for AGC is determined by
C1 (10µF) and R1(220kΩ).
6
2
4
Logic Circuit
3
5
30
31
32
7
PANASONIC [ PANASONIC SEMICONDUCTOR ]
