UNISONIC TECHNOLOGIES CO., LTD MC34118

UNISONIC TECHNOLOGIES CO., LTD
MC34118
LINEAR INTEGRATED CIRCUIT
VOICE SWITCHED
SPEAKER-PHONE CIRCUIT

DESCRIPTION
DIP-28
As a voice switched speaker-phone integrated circuit, the UTC
MC34118 includes the necessary amplifiers, attenuators, level
detectors and control algorithm.
To form the UTC MC34118’s internal circuit, there is an internal
microphone amplifier with adjustable gain and mute control, internal
transmit and Receive attenuators (operate in a complementary
manner), level detectors at both input and output of both attenuators,
and background noise monitors for both the transmit and receive
channels.
The dial tone can be pretended from being attenuated by the
receive background noise monitor circuit by a dial tone detector.
There are also two line driver amplifiers which can be used to form a
hybrid network in conjunction with an external coupling transformer. A
high-pass filter can be used for other filtering functions, and especially
to filter out 60Hz noise in the receive channel.
The UTC MC34118 which requiring typically 5mA may be
operated from a power supply, or it can be powered from the
telephone line.

SDIP-28
SOP-28
FEATURES
* Attenuator gain range: 52dB (between Transmit and Receive)
* For line-powered applications : 3~6.5V low voltage operation
* For improved sensitivity :4-point signal sensing
* For Transmit and Receive paths: background noise monitors
* External resistors set microphone amplifier gain
* Mute function included
* Chip disable: active or standby operation
* During dial tone presence: dial tone detector to inhibit receive idle
mode

ORDERING INFORMATION
Ordering Number
Lead Free
MC34118L-E28-T
-
Halogen Free
MC34118G-D28-T
MC34118G-E28-T
MC34118G-S28-T
MC34118G-S28-R
www.unisonic.com.tw
Copyright © 2014 Unisonic Technologies Co., Ltd
Package
Packing
DIP-28
SDIP-28
SOP-28
SOP-28
Tube
Tube
Tube
Tape Reel
1 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

MARKING
PACKAGE
MARKING
SOP-28
SSOP-28
DIP-28
SDIP-28

PIN CONFIGURATION
FO
FI
CD
VCC
HTO+
HTOHTI
TXO
TXI
MCO
MCI
MUT
VLC
CT
1
2
3
4
5
6
7
8
9
10
11
12
13
14
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
28
27
26
GND
25
24
23
22
21
20
19
RLO1
18
17
16
15
CPR
RLI1
TLO1
TLI1
RXO
RXI
RLI2
RLO2
TLO2
TL12
CPT
VB
2 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

PIN DESCRIPTION
PIN NO
1
2
PIN NAME
FO
FI
3
CD
4
VCC
5
HTO+
6
HTO-
7
8
HTI
TXO
9
TXI
10
11
MCO
MCI
12
MUT
13
VLC
14
CT
15
VB
16
17
CPT
TLI2
18
TLO2
19
20
RLO2
RLI2
21
RXI
22
23
RXO
TLI1
24
TLO1
25
26
27
28
RLO1
RLI1
CPR
GND
DESCRIPTION
Output of filter. The output impedance is less than 50Ω.
Input of filter. The input impedance is less than 1MΩ.
Chip Disable input .A logic low (voltage lower than 0.8V) sets normal operation. A logic
high (voltage higher than 2V) disable the IC. This pin’s input impedance is 90 KΩ
nominally.
This pin requires a supply voltage of +2.8V ~ +6.5V at 5mA. After VCC falls from 3.5V ~
2.8V, when in the receive mode, an AGC circuit reduces the receive attenuator gain by
25dB.
The output of the second hybrid amplifier. This amplifier’s gain is internally set at -1.
Output of the first hybrid amplifier. This amplifier’s gain of the amplifier is set by
external resistors.
The first hybrid amplifier’s input and summing node. DC level is about equal to VB.
The transmit attenuator’s output. DC level is about VB.
The transmit attenuator’s input. It’s maximum signal level is 350 mVrms. The input
impedance is 10KΩ.
The microphone amplifier’s output. This amplifier’s gain is set by external resistors.
The summing node of the microphone’s input. DC lever is VB.
Input of mute. A logic low (voltage lower than 0.8V) sets the circuit normal operation. A
logic high (voltage higher than 2V) mutes the microphone amplifier, but it doesn’t affect
the rest of the circuit. The input impedance is 90 K ohms.
The input of Volume control. In the receive mode, when VLC=VB, the receive
attenuator is at maximum gain. The receive gain is down 35dB when VLC=0.3dB, and
it does not effect the transmit modes.
At this pin, to switch modes, the RC sets the response time for the circuit.
In this pin, there’s an output voltage=Vcc/2 which is a system AC ground and biases
the volume control. What required is a filter capacitor.
The time constant for the transmit background side can be set by the RC at this pin .
The input to the transmit level detector which is on the microphone/ speaker side.
The output to the transmit level detector which is on the microphone/ speaker side.
Also the input to the transmit background monitor.
The Output of the receive level detector which is on the microphone/ speaker side
The input to the receive level detector which is on the microphone/ speaker side
The input to the receive attenuator and dial tone detector. In this pin, the maximum
input level is 350mVrms,and the input impedance is 10KΩ.
The output of the receive attenuator. This pin’s DC level is VB.
The input to the transmit level detector which is on the line side.
The output to the transmit level detector which is on the line side, and also the input to
the transmit background monitor.
The output of the receive level detector which is on the line side.
The input to the receive level detector which is on the line side.
The time constant for the receive background monitor can be set by the RC at this pin.
Ground.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
3 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

BLOCK DIAGRAM
MUT
MCO
TLI2
CT
TXI
TXO
TLI1
HTI
HTO-
HTO+
12
10
17
14
9
8
23
7
6
5
TX
Attenuator
MCI 11
CPT
TLO2
16
Background
Noise Monitor
19
CD
3
FI
2
VB
Background
Noise Monitor
AGC
18
RLO2
VB
Altenuator
Conrol
Level Delector
27
CPR
25
RLO1
24
TOL1
4
VCC
Lever Detector
RX
Attenuator
VB
1
20
13
22
FO
RLI2
VLC
RXO
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
21
26
15
RXI RLI1 VB
28
GND
4 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

ABSOLUTE MAXIMUM RATING (TA=25°С,Voltages referred to pin 22)
PARAMETER
SYMBOL
RATINGS
UNIT
Supply Voltage
VCC
-1~7
V
Voltage at Pin 3
V3
-1~VCC+1
V
Voltage at Pin 12 ( mute)
V12
-1~VCC +1
V
Voltage at Pin 13 ( VLC)
V13
-1~VCC+0.5
V
Voltage at Pin 9, Pin 21, and Pin 2
V9, 21, 2
-0.5~ VCC+0.5
V
Storage Temperature
TSTR
-65~+150
°С
Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.

RECOMMENDED OPERATION CONDITIONS
PARAMETER
Supply Voltage
Voltage at Pin 3
Voltage at Pin 12 ( MUTE)
Voltage at Pin 13 ( VLC)
IVB Current ( Pin 15)
Attenuator Input Signal Voltage at Pin 9, Pin 21
RXO, TXO(Pin8, Pin 22)
Load Current
MCO(Pin 10)
HTO-, HTO+(Pin 6, Pin5)
Ambient Operating Temperature

SYMBOL
V4
V3
V12
V13
IVB
V9, V21
TOPR
RATINGS
3.5~6.5
0~ VCC
0~ VCC
0.3×VB~VB
500
350
0~+-2
0~+-1
0~+-0.5
-20~+60
UNIT
V
V
V
V
µA
mVrms
mA
mA
mA
°С
ELECTRICAL CHARACTERISTICS (TA= 25°C, unless otherwise specified)
PARAMETER
Supply Voltages
V+ Supply Current
CD Input Resistance
High
CD Input Voltage
Low
VB Output Voltage
SYMBOL
ICC
RCD
VCDH
VCDL
VB
VB Output Resistance
VB Power Supply Rejection Ratio
Attenuators
RX Mode, RXI=150mVrms
RX Mode, RXI=150mVrms
Receive Attenuator
Gain Change
Gain
AGC Gain Change
(f=1kHz, VLC=VB)
Idle Mode, RXI=150mVrms
RX to TX Mode Range
Volume Control Range
RXO DC Voltage
RXO DC Voltage
RXO High Voltage
ROVB
PSRR
RXO Low Voltage
VRXOL
RXI Input Resistance
GRX
GRX
GRX1
GRX2
GRXI
GRX3
VCR
VRXO
VRXO
VRXOH
RRXI
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
TEST CONDITIONS
VCC=6.5V, CD=0.8V
VCC =6.5V, CD=2V
VCC =VCD=6.5V
VCC =3.5V
VCC =5V
IVB=1mA
CVB=220µF, f=1kHz
VCC=5V
VCC =3.5V
VCC =3.5V vs. VCC =5V
VCC =3.5V vs. VCC =5V
MIN
50
2
1.8
4
4
-0.5
-22
49
27
RX Mode
RX to TX Mode
IOUT=-1mA, RXI=VB+1.5V
IOUT=+1mA, RXI=VB-1V,
Output Measured with
Respect to VB
RXI<350mVrs
TYP
MAX UNIT
5.5
600
90
8
800
VCC
0.8
1.3
2.1
400
54
2.4
Ω
dB
6
8
6
8
0
+0.5
-25
-15
-20
-17
52
54
35
VB
+-10 +-150
3.7
7
mA
μA
kΩ
V
V
V
dB
dB
dB
dB
dB
dB
dB
V
mV
V
-1.5
-1
V
10
14
kΩ
5 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

ELECTRICAL CHARACTERISTICS(Cont.)
PARAMETER
Transmit Attenuator Gain (f=1kHz)
TX Mode, TXI=150mVrms
Idle Mode, TXI=150mVrms
TX to Rx Mode Range
TXO DC Voltage
TXO DC Voltage
TXO High Voltage
TXO Low Voltage
GTX
GTXI
GTXI
VTXO
VTXO
VTXOH
VTXOL
TXI Input Resistance
Gain Tracking
Attenuator Control
CT Voltage ( CT-VB)
SYMBOL
RTXI
GTR
RX Mode
Idle Mode
TX Mode
TEST CONDITIONS
TX
TX to RX Mode
IOUT=-1mA, TXI=VB+1.5V
IOUT =+1mA, TXI=VB-1V,
Output Measured with
Respect to VB
TXI<350mVrs
GRX+GTX, @TX, IDIE, RX
www.unisonic.com.tw
TYP
4
-22
49
6
8
dB
-20
-17
dB
52
54
dB
VB
V
+-30 +-150 mV
V
3.7
7
VLC=VB
CT Source Current
ICTR
(Switching to RX Mode)
CT Sink Current
ICTT
(Switching to TX Mode)
CT Slow Idle Current
ICTS
CT Fast Idle Internal Resistance
RFI
VLC Input Current
IVLC
Dial Tone Detector Threshold
VDT
Microphone Amplifier ( VMUT< 0.8V, AVCL=31dB, unless otherwise specified)
Output Offset
MCOVOS VMCO-VB, RF=180 kΩ
Open Loop Gain
AVOLM
F<100Hz
Gain Bandwidth
GBWM
Output High Voltage
VMCOH IOUT =1mA, VCC=5V
Output Low Voltage
VMCOL
IOUT =1mA
Input Bias Current
IBM
@MCI
f=1kHz, VMUT=2V
Muting(Gain)
GMT
300Hz<f<10kHz
MUT Input Resistance
RMUT
VCC=VMUT=6.5V
MUT High Input Voltage
VMUTH
MUT Low Input Voltage
VMUTL
Distortion
THDM 300Hz<f<10kHz
HYBID AMPLIFIER
HTO-Offset
HVOS
VHTO-~VB, RF=51kΩ
HTO- to HTO+ Offset
HBVOS
RF =51kΩ
Open Loop Gain
AVOLH
HTI to HTO-, F<100Hz
Gain Bandwidth
GBWH
Closed Loop Gain
AVCLH
HTO- to HTO+
Input Bias Current(@HTI)
IBH
HTO- High Voltage
VHT-H
IOUT =-5mA
HTO- Low Voltage
VHT-L
IOUT =+5mA
HTO+ High Voltage
VHT+H
IOUT =-5mA
HTO+ Low Voltage
VHT+L
IOUT =+5mA
Distortion
THDM 300Hz<f<10kHz
UNISONIC TECHNOLOGIES CO., LTD
MIN
-85
+40
1.5
10
-50
70
MAX UNIT
-1.5
-1
V
10
+-0.1
14
kΩ
dB
240
0
-240
-60
+60
0
2
-60
15
0
80
1
-40
+85
3.6
20
50
3.7
200
-40
-55
50
2
0
Vcc
0.8
-0.35
0
0
80
1
0
-30
20
30
0.35
3.7
250
3.7
450
0.3
mV
dB
MHz
V
mV
nA
dB
-68
90
0.15
-20
-30
60
mV
mV
mV
µA
µA
µA
kΩ
nA
mV
kΩ
V
V
%
mV
mV
dB
MHz
dB
nA
V
mV
V
mV
%
6 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

ELECTRICAL CHARACTERISTICS(Cont.)
PARAMETER
SYMBOL
TEST CONDITIONS
Level Detectors And Background Noise Monitors
Transmit-Receive Switching
Threshold( Ratio of Current at RLI1+RLI2 to
ITH
20A at TLI1+TLI2 to Switch from Tx to Rx)
Source Current at RLO1, RLO2, TLO1, TLO2
ILSO
Sink Current at RLO1, RLO2, TLO1, TLO2
ILSK
CPR, CPT Output Resistance
RCP
IOUT =1.5mA
CPR, CPT Leakage Current
ICPLK
Filter
Voltage Offset at FO
FOVOS
VFO-VB, 220kΩ from VB to FI
FO Sink Current
IFO
FI Bias Current
IFI
SYSTEM Distortion (f=1kHz)
from FI to RXO,
RX Mode
THDR
FO connected to RXI
from MCI to HTO-/HTO+,
TX Mode
THD
includes TX attenuator

MIN
TYP
0.8
1
MAX UNIT
1.2
-2
4
35
-0.2
-200
150
mA
µA
Ω
µA
-90
260
-50
0
400
mV
µA
nA
0.5
3
%
0.8
3
%
TEMPERATURE PARAMETERS
PARAMETER
VCC Supply Current(CD=0.8V)
VCC Supply Current(CD=2V)
VB Output Voltage (VCC =5V)
Attenuator Gain (Max Gain)
Attenuator Gain (Max Attenuation)
Attenuator Input resistance
Dial Tone Detector Threshold
CT Source, Sink Current
Microphone, Hybrid Amplifier Offset
Transmit-Receive Switching Threshold
Sink Current at RLO1, RLO2, TLO1, TLO2
Closed Loop Gain( HTO- to HTO+)
TYP RATINGS (TA=25°С)
5mA
400µA
2.1V
6
-46dB
10kΩ
15mV
±60µA
0mV
1
4µA
0dB
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
TYP CHANGE
-0.3
-0.4
+0.8
0.0008
0.004
0.6
20
-0.15
±4
±0.02
-10
0.001
UNIT
%/°С
%/°С
%/°С
dB/°С
dB/°С
%/°С
µV/°С
%/°С
µV/°С
%/°С
nA/°С
%/°С
7 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

FUNCTIONAL DESCRIPTION
INTRODUCTION
Between operation of a speakerphone and a handset, the fundamental difference is that of half-duplex versus
full-duplex. The UTC MC34118 includes the necessary level detectors, attenuators, and switching control for a
properly operating speakerphone. The detection sensitivity and timing can be externally controlled. The UTC
MC34118 also provides background noise monitors to make the circuit insensitive to room and line noise, hybrid
amplifier to interface to Tip and Ring, the microphone amplifier, and other associated functions.
ATTENUATORS
The transmit and receive attenuators are complementary in function, and they are never both fully on or both
fully off. For example, when one is at maximum gain: +6dB, the other is at maximum attenuation: -46dB, and vice
versa. But sum of their gains remains constant at -40dB typically. To control the transmit and receive paths to
provide the half-duplex operation required in speakerphone is the attenuators’ purpose. The attenuators are
non-inverting, have a -3dB (from max gain) frequency of ~100kHz, their input impedance of each one is nominally
10kΩ, and to prevent distortion, their input signal should be limited to 350 mVrms(same as 990mvp-p). After the
output current limit (typically 2.5mA) is reached, the output impedance is<10Ω.
VB
10kΩ
TXI/RXI
4.0kΩ
96KΩ
To Attenuator Input
These attenuators can be controlled by the Control Block’s output signal. When the CT pin which measures the
signal is at +240mV with respect to VB, the circuit is in the receive mode and so receive attenuator is at +6dB. When
the CT voltage is equal to VB, the circuit is in an idle mode, and it also causing the attenuators’ gains to be halfway
between their fully on and fully off positions (typical -20 dB each). The most direct method to monitor the circuit’s
mode is monitoring the CT voltage (with respect to VB).
LEVEL DETECTORS
There are two level detectors on the receive side and two level detectors on the transmit side. The terms in
parentheses form one system, and the other terms form the second system. All the four level detectors are high
amplifiers which have back-to-back diodes in the feedback path, and then it is resulting in non-linear gain, which
permits operation over a wide dynamic range of speech levels. TLI1, TLI2, RLI1, and RLI2, the external resistor and
capacitor determine the sensitivity of each level detector. Through a diode each output charges an external capacitor
and limiting resistor, thus providing a DC representation of the input AC signal level. The capacitor and an internal
350Ω resistor provide the outputs’ quick rise time. And an internal current source and the capacitor set a slow decay
time. On the receive side, RLI1 is at the receive input receiving the same signal as at Tip and Ring, and RLI2 is at
the output of the speaker amplifier. On the transmit side, TLI2 is at the microphone amplifier, while TLI1 is at the
hybrid output.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
8 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

FUNCTIONAL DESCRIPTION(Cont.)
BACKGROUND NOISE MONITORS
To distinguish speech (consists of bursts) from background noise (a relatively constant signal level) is the main
purpose of the background noise monitors. There is one background noise monitor for the receive path and another
one for the transmit path. The receive background noise monitor is operated on by the RLI1-RLO1 level detector, as
same as the transmit background noise monitor is operated on by the TLI2-TLO2 level detector. By storing a DC
voltage representative of the respective noise levels in capacitors at CPR and CPT, the background noise can be
monitored. At these pins, the voltages have slow rise times which determined by the external RC, but fast decay
times. The voltage at the non-inverting input of the monitor’s output comparator won’t be more positive than the
voltage at CPR/CPT when the signal at RLI1/TLI2 changes slowly. But while speech is present, it will rise quicker
than the voltage at the inverting input, causing its output to change. The term’s output is sensed by the attenuator
Control Block.
VOLUME CONTROL
At VLC (pin 13) is the volume control input which is sensed as a voltage with respect to VB. Only in the receive
mode the volume control affects the attenuators. In the receive mode, the receive attenuator’s gain will be +6dB, and
the transmit attenuator’s gain will be -46dB when VLC is equal to VB. When VLC is reduced below VB, the receive
attenuator’s gain is reduced, and the transmit attenuator’s gain is increased, but the sum of them tow remains
constant. Out of the pin VLC, the bias current is typically 60nA.
DIAL TONE DETECTOR
This detector is a comparator with one side connected to RXI and one side input connected to VB with a 15mV
offset. Under this situation: the circuit is in the receive mode, and the incoming signal is greater than 15Mv, the
comparator’s output will change, disabling the receive idle mode. Then receive attenuator will be at a setting only
determined by the volume control.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
9 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
10 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

FUNCTIONAL DESCRIPTION(Cont.)
AGC
The AGC circuit only affects the circuit under such situation: when the circuit is in the receive mode, and when
VCC is less than 3.5v. As while as VCC 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
TX
TX
1
X
TX
RX
Y
Y
RX
TX
Y
Y
RX
RX
X
1
TX
TX
0
X
TX
RX
0
0
RX
TX
0
0
RX
RX
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
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
OUTPUT
Transmit Mode
Fast Idle Mode
Fast Idle Mode
Receive Mode
Slow Idle Mode
Slow Idle Mode
Slow Idle Mode
Slow Idle Mode
11 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

FUNCTIONAL DESCRIPTION(Cont.)
Definition of the above is as follows:
Trems
Definition
Transmit
The transmit attenuator is fully on: +6dB. And the receive attenuator is at max. attenuation :-46dB
Both attenuators are controlled by the volume control. At max. Volume the receive attenuator is fully
Receive
on: +6dB, and the transmit attenuator is at max.attenuation:-46dB.
Both transmit and receive speech are present in approximately equal levels.
Fast Idle
The attenuators are quickly switched to idle until one speech level dominates the other.
Speech has ceased in both transmit and receive paths. The attenuators are then slowly switched to
Slow Idle
the idle mode.
A summary of the truth table is:
1. Under all the below situations the circuit will switch to transmit :
(1) Both transmit level detectors sense signals relative to the respective receive level detectors
TLI1 versus RLI1, TLI2 versus RLI2
(2) The transmit background noise monitor indicates the presence of speech.
2. Under all the below situations the circuit will switch to receive
(1) Both receive level detectors sense higher signal levels relative to the respective transmit level detectors
(2) The receive background noise monitor indicates the presence of speech.
3. Under all the below situations the circuit will switch to the fast Idle mode:
(1) If the level detectors disagree on the relative strengths of the signal levels
(2) At least one of the background noise monitor indicates speech.
There are two conditions which can cause the fast idle mode to occur:
(A) When both talkers are attempting to gain control of the system by talking at the same time
(B) When one talker is in a very noisy environment, forcing the other to continually over-ride that noise level. In
general, the fast idle mode will occur infrequently.
4. Under any of the below situations the circuit will switch to the slow idle mode
(1) Both talkers are quiet( no speech present)
(2) When one talker’s speech level is continuously over-ride by noise at the other speaker’s location.
CT pin (pin14) determine the time required to switch the circuit between transmit, receive, fast idle, and slow
idle.
A schematic of the CT circuitry operates as follows:
* RT =120kΩ (typ.), and CT =5µF (typ.).
* Switching to the receive mode
I1 is turned on; I2 is off,
Charging the external capacitor to +240mV above VB
An internal clamp prevents further charging of the capacitor).
* Switching to the transmit mode
I2 is turned on; I1 is off,
Bringing down the voltage on the capacitor to -240mV with respect VB.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
12 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

*
*
FUNCTIONAL DESCRIPTION(Cont.)
Switch to idle quickly,
The current sources are turned off,
The internal 2kΩ resistor is switched in
Discharging the capacitor to VB with a time = 2kΩ x CT.
Switching to idle slowly
The current sources are turned off
The switch at the 2kΩ resistor is open
Discharging the capacitor to VB through the external resistor RT with a time=RT x CT.
MICROPHONE AMPLIFIER
While the inverting input and the output are pinned out, pins 10/11,the microphone amplifier, has the
non-inverting input internally connected to VB. This amplifier’s open loop gain is typically 80dB when f<100Hz, and
the gain bandwidth is typically 1MHz. Its maximum output swing (p-p) is typically 1 volt. MCI’s input bias current is
typically 40nA out of the pin.
HYBRID AMPLIFIER
At HTO+, HTO-, and HTI, the two hybrid amplifiers provide the two-to-four wire converter for interfacing to the
telephone line. The first amplifier’s gain is set by external resistor, and the first amplifier’s output drives the second
amplifier (gain of -1).
FILTER
The external components determined the operation of the filter circuit.
POWER SUPPLY, VB, and CHIP DISABLE
For normal operation the power supply voltage is to be between 3.5v and 6.5v, but with reduced operation the
VCC is possible 2.8 volts. VB’s output voltage is ~ (Vcc-0.7)/2, and also provides the AC ground.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
13 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118

TYPICAL APPLICATION CIRCUIT
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
14 of 15
QW-R108-007.F
UNISONIC TECHNOLOGIES CO., LTD
LINEAR INTEGRATED CIRCUIT
MC34118
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or
other parameters) listed in products specifications of any and all UTC products described or contained
herein. UTC products are not designed for use in life support appliances, devices or systems where
malfunction of these products can be reasonably expected to result in personal injury. Reproduction in
whole or in part is prohibited without the prior written consent of the copyright owner. The information
presented in this document does not form part of any quotation or contract, is believed to be accurate
and reliable and may be changed without notice.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
15 of 15
QW-R108-007.F