U4082B_15 Datasheet, PDF (10/13 Pages) Unisonic Technologies – VOICE SWITCHED SPEAKER-PHONE CIRCUIT

UNISONIC TECHNOLOGIES CO., LTD
U4082B
LINEAR INTEGRATED CIRCUIT
„ FUNCTIONAL DESCRIPTION(Cont.)
AGC
The AGC circuit only affects the circuit under such situation: when the circuit is in the receive mode, and when
V_CC is less than 3.5v. As while as V_CC falls below 3.5 volts, the transmit path attenuation changes so that the sum of
the transmit and receive gains remains constant.
ATTENUATOR CONTROL BLOCK
This block has the seven:
* C1: The output of the comparator operated by RLO2 and TLO2 (here means in microphone/ speaker side).
* C2: The output of the comparator operated by RLO1 and TLO1 (here means Tip/ Ring side).
* C3: The output of the transmit background noise monitor.
* C4: The output of the receive background noise monitor.
* Volume control
* Dial tone detector
* AGC circuit
The C1~C4 effect is as follows:
INPUTS
C1
C2
C3
C4
T_X
T_X
1
X
T_X
R_X
Y
Y
R_X
T_X
Y
Y
R_X
R_X
X
1
T_X
T_X
0
X
T_X
R_X
0
0
R_X
T_X
0
0
R_X
R_X
X
0
Switching to the full transmit or receive from any other mode is at the fast rate (~30 ms).
X :Don’t care
Y :C3,C4 are not both 0
OUTPUT
Transmit Mode
Fast Idle Mode
Fast Idle Mode
Receive Mode
Slow Idle Mode
Slow Idle Mode
Slow Idle Mode
Slow Idle Mode
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
10 of 13
QW-R108-020.A