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MC34118G-S28-R

更新时间：2024-10-29 11:36:50

品牌：UTC

描述：VOICE SWITCHED SPEAKER-PHONE CIRCUIT

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MC34118G-S28-R 概述

VOICE SWITCHED SPEAKER-PHONE CIRCUIT 话音切换免提电话线路电话电路

MC34118G-S28-R 规格参数

是否Rohs认证：	符合	生命周期：	Active
零件包装代码：	SOIC	包装说明：	HALOGEN FREE, SOP-28
针数：	28	Reach Compliance Code：	compliant
HTS代码：	8542.39.00.01	风险等级：	5.58
JESD-30 代码：	R-PDSO-G28	长度：	17.7 mm
功能数量：	1	端子数量：	28
最高工作温度：	60 °C	最低工作温度：	-20 °C
封装主体材料：	PLASTIC/EPOXY	封装代码：	SOP
封装等效代码：	SOP28,.4	封装形状：	RECTANGULAR
封装形式：	SMALL OUTLINE	峰值回流温度（摄氏度）：	NOT SPECIFIED
电源：	3.5/6.5 V	认证状态：	Not Qualified
座面最大高度：	2.8 mm	子类别：	Telephone Circuits
最大压摆率：	0.008 mA	标称供电电压：	5 V
表面贴装：	YES	技术：	BIPOLAR
电信集成电路类型：	SPEAKER PHONE CIRCUIT	温度等级：	OTHER
端子形式：	GULL WING	端子节距：	1.27 mm
端子位置：	DUAL	处于峰值回流温度下的最长时间：	NOT SPECIFIED
宽度：	7.65 mm	Base Number Matches：	1

MC34118G-S28-R 数据手册

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UNISONIC TECHNOLOGIES CO., LTD

MC34118

LINEAR INTEGRATED CIRCUIT

VOICE SWITCHED

SPEAKER-PHONE CIRCUIT

SOP-28

DESCRIPTION

As a voice switched speaker-phone integrated circuit, the UTC

MC34118 includes the necessary amplifiers, attenuators, level

detectors and control algorithm.

DIP-28

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.

SDIP-28

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.

Lead-free:

Halogen-free: MC34118G

MC34118L

The UTC MC34118 which requiring typically 5mA may be

operated from a power supply, or it can be powered from the

telephone line.

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

Package

Packing

Normal

Lead Free Plating

MC34118L-D28-T

MC34118L-E28-T

MC34118L-S28-T

MC34118L-S28-R

Halogen Free

MC34118-D28-T

MC34118-E28-T

MC34118-S28-T

MC34118-S28-R

MC34118G-D28-T

MC34118G-E28-T

MC34118G-S28-T

MC34118G-S28-R

DIP-28

SDIP-28

SOP-28

Tube

Tape Reel

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QW-R108-007,D

MC34118

LINEAR INTEGRATED CIRCUIT

PIN DESCRIPTION

PIN NO

PIN NAME

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 V_CCfalls from 3.5V ~

2.8V, when in the receive mode, an AGC circuit reduces the receive attenuator gain by

25dB.

V_CC

HTO+

HTO-

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.

HTI

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.

TXO

The transmit attenuator’s input. It’s maximum signal level is 350 mVrms. The input

impedance is 10Kꢀ.

TXI

MCO

MCI

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.

MUT

VLC

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.

CPT

TLI2

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.

TLO2

RLO2

RLI2

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 10Kꢀ.

RXI

RXO

TLI1

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.

TLO1

RLO1

RLI1

CPR

GND

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.

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MC34118

LINEAR INTEGRATED CIRCUIT

BLOCK DIAGRAM

MUT MCO

TLI2

TXI

HTI

HTO+

TXO

TLI1

HTO-

T_X

Attenuator

MCI

Background

Noise Monitor

Background

Noise Monitor

CPT 16

TLO2 18

CPR

25 RLO1

AGC

Altenuator

Conrol

TOL1

V_CC

Level Delector

Lever Detector

RLO2 19

R_X

Attenuator

RLI2

RXO

21 26 15

RXI RLI1 VB

VLC

GND

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MC34118

LINEAR INTEGRATED CIRCUIT

ABSOLUTE MAXIMUM RATING (Ta=25°С,Voltages referred to pin 22)

PARAMETER

SYMBOL

V_CC

RATINGS

-1~7

UNIT

Supply Voltage

Voltage at Pin 3

-1~V_CC+1

-1~V_CC+0.5

-0.5~ V_CC+0.5

-65~+150

Voltage at Pin 12 ( mute)

Voltage at Pin 13 ( VLC)

Voltage at Pin 9, Pin 21, and Pin 2

Storage Temperature

V12

V13

V9, 21, 2

T_STR

°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

SYMBOL

RATINGS

3.5~6.5

UNIT

Supply Voltage

Voltage at Pin 3

0~ V_CC

Voltage at Pin 12 ( MUTE)

V12

0~ V_CC

0.3×VB~VB

Voltage at Pin 13 ( VLC)

V13

IVB Current ( Pin 15)

I_VB

500

350

µA

Attenuator Input Signal Voltage at Pin 9, Pin 21

V9, V21

mVrms

°С

RXO, TXO(Pin8, Pin 22)

MCO(Pin 10)

0~+-2

0~+-1

0~+-0.5

-20~+60

Load Current

HTO-, HTO+(Pin 6, Pin5)

Ambient Operating Temperature

T_OPR

ELECTRICAL CHARACTERISTICS (Ta=25°C)

PARAMETER

SYMBOL

TEST CONDITIONS

MIN TYP MAX UNIT

Supply Voltages

V+ Supply Current

CD Input Resistance

V_CC=6.5V, CD=0.8V

5.5

μA

kꢀ

I_CC

V_CC=6.5V, CD=2V

600 800

R_CD

V_CDH

V_CDL

V_CC=V_CD=6.5V

High

V_CC

0.8

1.3

CD Input Voltage

V_BOutput Voltage

Low

V_CC=3.5V

V_CC=5V

I_VB=1mA

V_B

1.8

2.1

400

2.4

V_BOutput Resistance

V_BPower Supply Rejection Ratio

Attenuators

R_OVB

ꢀ

PSRR C_VB=220µF, f=1kHz

R_XMode, R_XI=150mVrms

G_RX

V_CC=5V

R_XMode, R_XI=150mVrms

Gain Change

V_CC=3.5V

Receive Attenuator

Gain

(f=1kHz, V_LC=V_B)

ΔG_RX1V_CC=3.5V vs. V_CC=5V

-0.5

+0.5 dB

AGC Gain Change

ΔG_RX2V_CC=3.5V vs. V_CC=5V

-25

-20

V_B

-15

-17

Idle Mode, R_XI=150mVrms

R_Xto T_XMode Range

G_RXI

ΔG_RX3

V_CR

-22

Volume Control Range

R_XODC Voltage

V_RXO

R_XMode

ΔR_XODC Voltage

R_XOHigh Voltage

ΔV_RXOR_Xto T_XMode

+-10 +-150 mV

V_RXOH

V_RXOL

R_RXI

I_OUT=-1mA, R_XI=V_B+1.5V

3.7

I_OUT=+1mA, R_XI=V_B-1V,

Output Measured with

Respect to V_B

R_XOLow Voltage

-1.5

-1

R_XIInput Resistance

R_XI<350mVrs

kꢀ

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MC34118

LINEAR INTEGRATED CIRCUIT

ELECTRICAL CHARACTERISTICS(Cont.)

PARAMETER

SYMBOL

TEST CONDITIONS

MIN TYP MAX UNIT

Transmit Attenuator Gain (f=1kHz)

T_XMode, T_XI=150mVrms

Idle Mode, T_XI=150mVrms

T_Xto Rx Mode Range

T_XO DC Voltage

G_TX

G_TXI

-22

-20

-17

ΔG_TXI

V_TXO

T_X

ΔT_XODC Voltage

T_XOHigh Voltage

ΔV_TXOT_Xto R_XMode

V_TXOHI_OUT=-1mA, T_XI=V_B+1.5V

+-30 +-150 mV

3.7

I_OUT=+1mA, T_XI=V_B-1V,

Output Measured with

Respect to V_B

T_XOLow Voltage

V_TXOL

-1.5

-1

T_XIInput Resistance

Gain Tracking

R_TXI

G_TR

T_XI<350mVrs

G_RX+G_TX, @T_X, I_DIE, R_X

kꢀ

+-0.1

Attenuator Control

R_XMode

V_LC=V_B

240

µA

kꢀ

CT Voltage ( CT-V_B)

Idle Mode

T_XMode

-240

-60

CT Source Current

I_CTR

I_CTT

I_CTS

R_FI

(Switching to R_XMode)

(Switching to T_XMode)

-85

-40

CT Sink Current

+40 +60 +85

CT Slow Idle Current

CT Fast Idle Internal Resistance

VLC Input Current

1.5

3.6

I_VLC

V_DT

-60

Dial Tone Detector Threshold

Microphone Amplifier ( V_MUT< 0.8V, A_VCL=31dB, unless otherwise specified)

Output Offset

M_COVOSV_MCO-V_B, R_F=180 kꢀ

-50

Open Loop Gain

Gain Bandwidth

Output High Voltage

Output Low Voltage

Input Bias Current

A_VOLM

G_BWM

F<100Hz

MHz

V_MCOHI_OUT=1mA, V_CC=5V

3.7

-55

V_MCOL

I_BM

I_OUT=1mA

200 mV

@MCI

-40

f=1kHz, V_MUT=2V

300Hz<f<10kHz

V_CC=V_MUT=6.5V

Muting(ΔGain)

G_MT

-68

MUT Input Resistance

MUT High Input Voltage

R_MUT

V_MUTH

V_MUTL

kꢀ

Vcc

0.8

MUT Low Input Voltage

Distortion

THD_M300Hz<f<10kHz

0.15

HYBID AMPLIFIER

HTO-Offset

H_VOS

H_BVOS

A_VOLH

G_BWH

A_VCLH

I_BH

V_HTO-~V_B, R_F=51kꢀ

R_F=51kꢀ

-20

-30

HTO- to HTO+ Offset

Open Loop Gain

Gain Bandwidth

H_TIto H_TO-, F<100Hz

MHz

Closed Loop Gain

Input Bias Current(@HTI)

HTO- High Voltage

HTO- Low Voltage

HTO+ High Voltage

HTO+ Low Voltage

Distortion

H_TO-to H_TO+

-0.35

3.7

0.35 dB

-30

V_HT-H

V_HT-L

V_HT+H

V_HT+L

I_OUT=-5mA

I_OUT=+5mA

I_OUT=-5mA

I_OUT=+5mA

250 mV

3.7

450 mV

THD_M300Hz<f<10kHz

0.3

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MC34118

LINEAR INTEGRATED CIRCUIT

ELECTRICAL CHARACTERISTICS(Cont.)

PARAMETER

SYMBOL

TEST CONDITIONS

MIN TYP MAX UNIT

Level Detectors And Background Noise Monitors

Transmit-Receive Switching

Threshold( Ratio of Current at RLI1+RLI2 to

20μA at TLI1+TLI2 to Switch from Tx to Rx)

Source Current at RLO1, RLO2, TLO1, TLO2

Sink Current at RLO1, RLO2, TLO1, TLO2

CPR, CPT Output Resistance

CPR, CPT Leakage Current

Filter

I_TH

0.8

1.2

I_LSO

I_LSK

-2

µA

ꢀ

R_CP

I_CPLK

I_OUT=1.5mA

-0.2

µA

Voltage Offset at FO

F_OVOS

I_FO

V_FO-V_B, 220kꢀ from V_Bto FI

-200 -90

µA

FO Sink Current

150 260 400

-50

FI Bias Current

I_FI

SYSTEM Distortion (f=1kHz)

from F_Ito R_XO

F_Oconnected to R_XI

R_XMode

T_XMode

THD_R

THD

0.5

0.8

from MCI to H_TO-/H_TO+

includes T_Xattenuator

TEMPERATURE PARAMETERS

PARAMETER

TYP RATINGS (Ta=25°С)

TYP CHANGE

-0.3

UNIT

V_CCSupply Current(CD=0.8V)

V_CCSupply Current(CD=2V)

5mA

400µA

2.1V

%/°С

dB/°С

%/°С

µV/°С

%/°С

µV/°С

%/°С

nA/°С

%/°С

-0.4

V_BOutput Voltage (V_CC=5V)

+0.8

Attenuator Gain (Max Gain)

0.0008

0.004

0.6

Attenuator Gain (Max Attenuation)

Attenuator Input resistance

-46dB

10kꢀ

15mV

±60µA

0mV

Dial Tone Detector Threshold

CT Source, Sink Current

-0.15

±4

Microphone, Hybrid Amplifier Offset

Transmit-Receive Switching Threshold

Sink Current at RLO1, RLO2, TLO1, TLO2

Closed Loop Gain( HTO- to HTO+)

±0.02

-10

4µA

0dB

0.001

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MC34118

LINEAR INTEGRATED CIRCUIT

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

10kꢀ, 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<10ꢀ.

10kꢀ

TXI/RXI

To Attenuator Input

4.0kꢀ

96Kꢀ

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

350ꢀ 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.

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MC34118

LINEAR INTEGRATED CIRCUIT

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.

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MC34118

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

_CCis less than 3.5v. As while as V_CCfalls 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

OUTPUT

T_X

R_X

T_X

R_X

T_X

R_X

T_X

R_X

T_X

R_X

T_X

R_X

Transmit Mode

Fast Idle Mode

Receive Mode

Slow Idle Mode

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

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MC34118

LINEAR INTEGRATED CIRCUIT

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

on: +6dB, and the transmit attenuator is at max.attenuation:-46dB.

Receive

Both transmit and receive speech are present in approximately equal levels.

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

the idle mode.

Fast Idle

Slow Idle

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 =120kꢀ (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.

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MC34118

LINEAR INTEGRATED CIRCUIT

FUNCTIONAL DESCRIPTION(Cont.)

Switch to idle quickly,

The current sources are turned off,

The internal 2kꢀ resistor is switched in

Discharging the capacitor to VB with a time = 2kꢀ x CT.

Switching to idle slowly

The current sources are turned off

The switch at the 2kꢀ 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

V_CCis possible 2.8 volts. VB’s output voltage is ~ (Vcc-0.7)/2, and also provides the AC ground.

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MC34118

LINEAR INTEGRATED CIRCUIT

TYPICAL APPLICATION CIRCUIT

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.

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