CONTEK MC34018 Datasheet

MC34018 LINEAR INTEGRATED CIRCUIT

VOICE SWITCHED SPEAKER­PHONE CIRCUIT

DESCRIPTION

The Contek MC34018 speaker-phone integrated circuit
incorporates the necessary functions to produce a high quality
hands-free speaker-phone system. The applications include
household and office speaker-phones, intercom systems,
hand free kit for mobile phones, and others.

FEATURES

*All necessary level detection and attenuation controls for a

hand-free telephone included.
*Background noise level monitoring with long time constant.
*Background sound level compensation for transmit and

receive levels as well as the background level.
*Wide operating dynamic range through signal compression.
*On-chip voltage regulators illuminate external regulators for

lining operation.
*Power audio amplifier for typical 100mW output (into 25

ohms)with peak limiting for speaker to minimize distortion.
*Chip Select pin for active/stand by operation.
*Volume control function for external volume control.
*Standard 28-pin plastic DIP and SOP package.

ABSOLUTE MAXIMUM RATINGS(Ta=25 C,Voltages referred to pin 22)

PARAMETER VALUE UNIT

V+ terminal Voltage (pin 16) +12,-1.0 V

CS

(pin 18)
Speaker amplifier Ground(pin 14) +3.0,-1.0 V
VLC(pin 24) +VCC,-1.0 V
Storage temperature -65 ~ +150 C

+12,-1.0 V

SOP-28

DIP-28

RECOMMENDED OPERATION CONDITIONS

PARAMETER VALUE UNIT

V+ Terminal Voltage (pin 16) +6.0 to +11 V

CS

(pin 18)
Icc(pin 20) 0 to 3.0 mA
VLC(pin 24) 0.55VB to VB V
Receive Signal(pin 27) 0 to 250 mVrms
Microphone Signal(pin 9) 0 to 5.0 mVrms
Speaker Amplifier Ground (pin 14) -10 to +10 mVdc
Ambient Temperature -20 to +60 C

0to+11 V

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1

MC34018 LINEAR INTEGRATED CIRCUIT

BLOCK DIAGRAM

MIC

SPEAKER

Contek

RECEIVE

CHANNEL

MIC AMP

PEAK LIMITER

SIGNAL/NOISE

DETECTOR

SPEAKER
AMP

TRANSMIT

CHANNEL

ATTENUATOR

CONTROL

RECEIVE VOLUME CONTROL

TRANSMIT

ATTENUATOR

RECEIVE

ATTENUATOR

TRANSMIT/

RECEIVE

COMPARATOR

REGULATOR

TRANSMIT LEVEL

DETECTOR

RECEIVE LEVEL

DETECTOR

VCC

ENABLEINPUT

SIDE

TONE

TRANSMIT

OUTPUT

DC INPUT

SIDE TONE
NETWORK

RECEIVEINPUT

TELEPHONE

LINE

PIN CONFIGURATIONS

PIN NAME DESCRIPTION

1 RR A resistor to ground provides a reference current for the transmit and receive attenuators
2 RTX A resistor to ground determines the nominal gain of the transmit attenuator ,the transmit channel gain

3 TXI Input to the transmit attenuator. Input resistance is nominally 5.0k ohms.
4 TXO Output of the transmit attenuator. The TXO output signal drivers the input of transmit level detcetor, as

5 TLI Input of the transmit level detector. An external resistor ac coupled to The TLI pin sets the detection

6 TLO Output of the transmit level detector. The external resistor and capacitor set the time the comparator

7 RLI Input of the receive level detector. An external resistor ac coupled to The RLI pin sets the detection

8 RLO Output of the receive level detector. The external resistor and capacitor set the time the comparator

9 MCI Microphone amplifier input. Input impedance is nominally 10k ohms and the dc bias voltage is

10 MCO Microphone amplifier output. The MIC amp gain is internally set at 34dB(50V/V).
11 CP1 A parallel resistor and capacitor connected between this pin and VCC holds a voltage corresponding

12 CP2 A capacitor at this pin peak detects the speech signals for comparison with the background noise level

13 XDI Input to the transmit detector system. The microphone amplifier output is ac coupled to the XDI pin

is inversely proportional to RTX resistance.

well as the external circuit which drivers the telephone line.

level. Decreasing this resistor increases the sensitivity to transmit channel signals.

will hold the system in the transmit mode after speech ceases.

level. Decreasing this resistor increases the sensitivity to receive channel signals.

will hold the system in the receive mode after speech ceases.

approximately equal to VB

to the background noise level. The transmit detector compares the CP1 voltage with the speech signal
from CP2.

held at CP1.

through an external resistor.

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MC34018 LINEAR INTEGRATED CIRCUIT

(continued)

PIN NAME DESCRIPTION

14 SKG High current ground pin for the speaker amplifier output stage. The SKG voltage should be within

10mV of the ground voltage at pin 22.

15 SKO Speaker amplifier output. The SKO pin will source and sink up to 100mA when ac coupled to the

speaker. The speaker amplifier gain is internally set at 34dB(50V/V).

16 V+ Input DC supply voltage. V+ can be powered from Tip and Ring if an ac decoupling inductor is used to

prevent loading ac line signals. The required V+ voltage is 6.0V to 11V(7.5V nominal ) at 7.0mA.

17 AGC A capacitor from this pin to VB stabilizes the speaker amplifier gain control loop, and additionally

controls the attack and decay time of this circuit. The gain control loop limits the speaker amplifier
input to prevent clipping at SKO. The internal resistance at AGC pin is nominally 110k ohms.

CS

18

19 SKI Input to the speaker amplifier. Input impedance is nominally 20k ohms.
20 VCC A 5.4V regulated output which powers all circuits except the speaker amplifier output stage. VCC can

21 VB An output voltage equal to approximately VCC/2 which series as an analog ground for the

22 GND Ground pin for the IC(except the speaker amplifier)
23 XDC Transmit detector output. A resistor and capacitor at his pin hold the system in the transmit mode

24 VLC Volume control input>connecting this pin to the slider of a variable resistor provides receive mode

25 ACF Attenuator control filter. A capacitor connected to this pin reduces noise transient as the attenuator

26 RXO Output of the receive attenuator. Normally this pin is ac coupled to the input of the speaker amplifier.
27 RXI Input of the receive attenuator. Input impedance is nominally is 5.0k ohms.
28 RRX A resistor to ground determines the nominal gain of the receive attenuator. The receive channel gain

Digital chip select input. When at a logic "0" (<0.7V) the VCC regulator is enabled. When at a logic "1"
(>1.6V),the chip is in the standby mode drawing 0.5mA.An open
is nominally 140k ohms. The input voltage should not exceed 11V.

be used to power external circuitry such as a microprocessor(3.0mA max.) A filter capacitor is
required.TheContek MC34018 can be powered by a separate regulated supply by connecting V+ and
VCC to a voltage between 4.5V and 6.5V while maintaining

speakerphone system. Up to 1.5mA of external load current may be sourced from VB. Output
impedance is 250 ohms. A filter capacitor is required.

during pauses between words or phrases. When the XDC pin voltage decays to ground, the
attenuators switch from the transmit mode to idle mode. The internal resistor at XDC is nominally 2.6k
ohms(see fig.1).

volume control. The VLC pin voltage should be less than or equal to VB.

control switches level of attenuation.

is directly proportional to the RRX resistance.

CS

pin is a logic "0".Input impedance

CS

at a logic "1".

ELECTRICAL CHARACTERISTICS(referred to fig. 1)

PARAMETER SYMBOL MIN TYP MAX UNIT

SUPPLY VOLTAGES
V+ Supply Current

V+=11V,Pin 18=0.7V

V+=11V,Pin 18=1.6V
VCC Voltage(V+=7.5V)

Line

Regulation(6.5V<V+<11V)

Output Resistance(I
Dropout Voltage(V+=5.0V)

VB Voltage(V+=7.5V)

Output Resistance(I

CC=3mA)

B=1.7mA)

IV+

Vcc

DVcc

RoVcc

Vccsat

Vb

Rovb

4.9 5.4

LN

2.5 2.9

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65

6.0
80

250

9.0

800

5.9

150

20

300

3.3 Vdc

mA

mA

Vdc

mV

ohms

mV

ohms

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MC34018 LINEAR INTEGRATED CIRCUIT

(continued)

PARAMETER SYMBOL MIN TYP MAX UNIT

ATTENUATORS
Receive Attenuator Gain(1.0kHz)
Rx Mode, Pin 24= VB, Pin 27 =
250Mvrms
Range (Rx to Tx Modes)
Idle Mode, Pin 27= 250mVrms
RXO Voltage (Rx Mode) VRXO 1.8 2.3 3.2 mV
Delta RXO Voltage (Switch from Rx
to Tx Mode)
RXO Sink Current (Rx mode) IRXOL 75 mA
RXO Source Current (Rx mode) IROXH 1.0 3.0 mA
RXI Input Resistance RRXI 3.5 5.0 8.0 kW
Volume Control Range (Rx
Attenuator Gain, Rx Mode,

0.6VB<Pin 24<VB
ATTENUATORS
Transmit Attenuator Gain (1.0kHz)
Tx Mode, Pin 3 = 250mVrms
Range, (Tx to Rx Mode)
Idle Mode, Pin 3 = 250Mvrms
TXO Voltage (Tx mode) VTXO 1.8 2.3 3.2 Vdc
Delta TXO Voltage (switch from Tc
to Rx Mode)
TXO Sink Current (Tx mode) ITXOL 75 mA
TXO Source Current (Tx mode) ITXOH 1.0 3.0 mA
TXO Input Resistance RTXI 3.5 5.0 8.0 kW
ACF Voltage (VCC-Pin 25 Voltage)

Rx Mode

Tx Mode

Idle Mode

SPEAKER AMPLIFIER
Speaker Amp Gain (pin 19 =
20mVrms)
SKI Input Resistance RSKI 15 22 37 kW
SKO Voltage ( Pin 19 =Cap couple
to GND)
SKO High Voltage ( Pin 19 = 0.1V,

-100mA Load at Pin 15)
SKO Low Voltage (pin 19=0.1V,
+100mA Load at Pin 15)
MICROPHONE AMPLIFIER
Microphone Amp Gain ( Pin 9 =
10mVrms,1KHz)
Microphone Amp Input Resistance RMCI 6.5 10 16 kW

G

RX

DGRX

GRI

DVRXO 100 mV

CR 24.5 32.5 dB

V

G

TX

DGTX

GTXI

DVTXO 100 mV

DV

ACF

GSPK 33 34 35 dB

VSKO 2.4 3.0 3.6 Vdc

VSKOH 5.5 Vdc

VSKOL 600 mV

GMCI 32.5 34 35 dB

2.0

40

-20

4.0
40

-16.5

6.0

44

-16

6.0
44

-13

150

6.0
75

10

48

-12

8.0
48

-8.5

dB

dB
dB

dB
dB
dB

mV
mV
mV

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4

MC34018 LINEAR INTEGRATED CIRCUIT

(continued)

PARAMETER SYMBOL MIN TYP MAX UNIT

LOGAMPS
RLO Leakage Current
(Pin 8 = VB+1.0V)
TLO Leakage Current
(Pin 6 = VB+1.0V)
Transmit-Receive Switching

Threshold (Ratio of I
20mA - to Switch Tx-Rx
Comparator)

TRANSMIT DETECTOR

XDC Voltage

Idle Mode

Tx Mode

CP2 Current Source ICP2 5.0 10 13 mA

Distortion

Rx Mode

RXI to SKO

(pin 27 = 10mVrms,1KHz)

Tx Mode

MCI to TXO

(Pin 9 = 5mVrms,1KHz)

Note 1:V+=7.5V,CS=0.7V except where noted.

Note 2:Rx mode:pin7=-100mA,pin5=+100mA, except where noted.

Idle mode: Pin 5=-100 mA, pin 7,13=+100mA.
Note 3:Current into a pin designed as + ,current out of a pin designed -;
Note 4:Voltage referred to pin 22,Tamb=25 C.

TLI to IRLI - at

Tx mode: pin 5,13=-100mA, pin 7=+100mA, pin 11=0V.

ILKRLO 2.0 mA

ILKTLO 2.0 mA

ITH 25

XDC 0

V

R

XD 1.5 %

XD 2.0 %

T

4.0

Vdc
Vdc

TEMPERATURE CHARACTERISTICS(-20 TO +60 C )

PARAMETER PIN TYP CHANGE UNIT

V+ Supply Current ( V+ 11V,Pin 18 = 0.7V ) 16 -0.2 %/ C
V+ Supply Current(V+ 11V,Pin 18 = 1.6V ) 16 -0.4 %/ C
VCC Voltage( V+ = 7.5V ) 20 +0.1 %/ C
Attenuator Gain ( Max and Min Setting ) +-0.003 dB/ C
Delta RXO,TXO Voltage 4,26 +-0.24 %/ C
Speaker AMP Gain 15,19 +-0.001 dB/ C
Microphone AMP Gain 9,10 +-0.4 dB/ C
Microphone Amp Input Resistance 9 +0.4 %/ C
Tx-Rx Switching Threshold (20mA) 5,7 +-0.2 nA/ C

DESIGN GUIDELINES(REF TO FIG. 1)

ATTENUATORS

The transmit and receive attenutors are complementary in function, i.e., when one is at maximum gain the other
is at maximum attenuator, and vice versa. They are never both on or both off. Their main purpose is to control the
transmit and receive paths to provide the half- duplx operation required of a speaker-phone. The attenuators are
controlled solely by the voltage at the ACF pin(pin 25).The ACF voltage is provided by the attenuator control block,

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