VOICE SWITCHED SPEAKER-PHONE CIRCUIT MC34018 speaker-phone integr
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MC34018 LINEAR INTEGRATED CIRCUIT
VOICE SWITCHED SPEAKER-PHONE CIRCUIT
MC34018 speaker-phone integrated circuit incorporates necessary functions produce high quality hands-free speaker-phone system. applications include household office speaker-phones, intercom systems, hand free mobile phones, others.
SOP-28
FEATURES
*All necessary level detection attenuation controls hand-free telephone included. *Background noise level monitoring with long time constant. *Background sound level compensation transmit receive levels well background level. *Wide operating dynamic range through signal compression. *On-chip voltage regulators illuminate external regulators lining operation. *Power audio amplifier typical 100mW output (into ohms)with peak limiting speaker minimize distortion. *Chip Select active/stand operation. *Volume control function external volume control. *Standard 28-pin plastic package.
DIP-28
ABSOLUTE MAXIMUM RATINGS(Ta=25°C,Voltages referred
PARAMETER
terminal Voltage (pin (pin Speaker amplifier Ground(pin VLC(pin Storage temperature
VALUE
+12,-1.0 +12,-1.0 +3.0,-1.0 +VCC,-1.0 +150
UNIT
RECOMMENDED OPERATION CONDITIONS
PARAMETER
Terminal Voltage (pin Icc(pin VLC(pin Receive Signal(pin Microphone Signal(pin Speaker Amplifier Ground (pin Ambient Temperature
(pin
VALUE
+6.0 0.55VB
UNIT
mVrms mVrms mVdc
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
BLOCK DIAGRAM
TRANSMIT CHANNEL TRANSMIT ATTENUATOR TRANSMIT LEVEL DETECTOR
TRANSMIT OUTPUT
SIGNAL/NOISE DETECTOR
ATTENUATOR CONTROL
TRANSMIT/ RECEIVE COMPARATOR
SIDE TONE
SIDE TONE NETWORK
PEAK LIMITER
RECEIVE LEVEL DETECTOR
SPEAKER
RECEIVE ATTENUATOR RECEIVE INPUT REGULATOR INPUT
SPEAKER
RECEIVE CHANNEL
TELEPHONE LINE
ENABLE INPUT RECEIVE VOLUME CONTROL
CONFIGURATIONS
NAME DESCRIPTION resistor ground provides reference current transmit receive attenuators resistor ground determines nominal gain transmit attenuator ,the transmit channel gain inversely proportional resistance. Input transmit attenuator. Input resistance nominally 5.0k ohms. Output transmit attenuator. output signal drivers input transmit level detcetor, well external circuit which drivers telephone line. Input transmit level detector. external resistor coupled sets detection level. Decreasing this resistor increases sensitivity transmit channel signals. Output transmit level detector. external resistor capacitor time comparator will hold system transmit mode after speech ceases. Input receive level detector. external resistor coupled sets detection level. Decreasing this resistor increases sensitivity receive channel signals. Output receive level detector. external resistor capacitor time comparator will hold system receive mode after speech ceases. Microphone amplifier input. Input impedance nominally ohms bias voltage approximately equal Microphone amplifier output. gain internally 34dB(50V/V). parallel resistor capacitor connected between this holds voltage corresponding background noise level. transmit detector compares voltage with speech signal from CP2. capacitor this peak detects speech signals comparison with background noise level held CP1. Input transmit detector system. microphone amplifier output coupled through external resistor.
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
(continued)
NAME
High current ground speaker amplifier output stage. voltage should within 10mV ground voltage Speaker amplifier output. will source sink 100mA when coupled speaker. speaker amplifier gain internally 34dB(50V/V). Input supply voltage. powered from Ring decoupling inductor used prevent loading line signals. required voltage 6.0V 11V(7.5V nominal 7.0mA. capacitor from this stabilizes speaker amplifier gain control loop, additionally controls attack decay time this circuit. gain control loop limits speaker amplifier input prevent clipping SKO. internal resistance nominally 110k ohms. Digital chip select input. When logic (<0.7V) regulator enabled. When logic (>1.6V),the chip standby mode drawing 0.5mA.An open logic "0".Input impedance nominally 140k ohms. input voltage should exceed 11V. Input speaker amplifier. Input impedance nominally ohms. 5.4V regulated output which powers circuits except speaker amplifier output stage. used power external circuitry such microprocessor(3.0mA max.) filter capacitor required. MC34018 powered separate regulated supply connecting voltage between 4.5V 6.5V while maintaining logic "1". output voltage equal approximately VCC/2 which series analog ground speakerphone system. 1.5mA external load current sourced from Output impedance ohms. filter capacitor required. Ground IC(except speaker amplifier) Transmit detector output. resistor capacitor hold system transmit mode during pauses between words phrases. When voltage decays ground, attenuators switch from transmit mode idle mode. internal resistor nominally 2.6k ohms(see fig.1). Volume control input>connecting this slider variable resistor provides receive mode volume control. voltage should less than equal Attenuator control filter. capacitor connected this reduces noise transient attenuator control switches level attenuation. Output receive attenuator. Normally this coupled input speaker amplifier. Input receive attenuator. Input impedance nominally 5.0k ohms. resistor ground determines nominal gain receive attenuator. receive channel gain directly proportional resistance.
ELECTRICAL CHARACTERISTICS(referred fig.
PARAMETER
SUPPLY VOLTAGES Supply Current V+=11V,Pin 18=0.7V V+=11V,Pin 18=1.6V Voltage(V+=7.5V) Line Regulation(6.5V<V+<11V) Output Resistance(ICC=3mA) Dropout Voltage(V+=5.0V) Voltage(V+=7.5V) Output Resistance(IB=1.7mA)
SYMBOL
UNIT
VccLN RoVcc Vccsat Rovb
ohms ohms
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
(continued)
PARAMETER
ATTENUATORS Receive Attenuator Gain(1.0kHz) Mode, 250Mvrms Range Modes) Idle Mode, 250mVrms Voltage Mode) Delta Voltage (Switch from Mode) Sink Current mode) Source Current mode) Input Resistance Volume Control Range Attenuator Gain, Mode, 0.6VB<Pin 24<VB ATTENUATORS Transmit Attenuator Gain (1.0kHz) Mode, 250mVrms Range, Mode) Idle Mode, 250Mvrms Voltage mode) Delta Voltage (switch from Mode) Sink Current mode) Source Current mode) Input Resistance Voltage (VCC-Pin Voltage) Mode Mode Idle Mode SPEAKER AMPLIFIER Speaker Gain (pin 20mVrms) Input Resistance Voltage =Cap couple GND) High Voltage 0.1V, -100mA Load Voltage (pin 19=0.1V, +100mA Load MICROPHONE AMPLIFIER Microphone Gain 10mVrms,1KHz) Microphone Input Resistance
SYMBOL
UNIT
VRXO VRXO IRXOL IROXH RRXI
24.5
32.5
GTXI VTXO VTXO ITXOL ITXOH RTXI VACF
-16.5
-8.5
GSPK RSKI VSKO VSKOH VSKOL
GMCI RMCI
32.5
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
(continued)
PARAMETER
LOGAMPS Leakage Current (Pin VB+1.0V) Leakage Current (Pin VB+1.0V) Transmit-Receive Switching Threshold (Ratio ITLI IRLI 20µA Switch Tx-Rx Comparator) TRANSMIT DETECTOR Voltage Idle Mode Mode Current Source Distortion Mode (pin 10mVrms,1KHz) Mode (Pin 5mVrms,1KHz)
SYMBOL
ILKRLO ILKTLO
UNIT
VXDC ICP2
Note 1:V+=7.5V, =0.7V except where noted. Note 2:Rx mode:pin7=-100µA,pin5=+100µA, except where noted. mode: 5,13=-100µA, 7=+100µA, 11=0V. Idle mode: 5=-100µA, 7,13=+100µA. Note 3:Current into designed +,current designed Note 4:Voltage referred 22,Tamb=25°C.
TEMPERATURE CHARACTERISTICS(-20 +60°C
PARAMETER
Supply Current 11V,Pin 0.7V Supply Current(V+ 11V,Pin 1.6V Voltage( 7.5V Attenuator Gain Setting Delta RXO,TXO Voltage Speaker Gain Microphone Gain Microphone Input Resistance Tx-Rx Switching Threshold (20µA)
4,26 15,19 9,10
CHANGE
-0.2 -0.4 +0.1 +-0.003 +-0.24 +-0.001 +-0.4 +0.4 +-0.2
UNIT
%/°C %/°C %/°C dB/°C %/°C dB/°C dB/°C %/°C nA/°C
DESIGN GUIDELINES(REF FIG.
ATTENUATORS
transmit receive attenutors complementary function, i.e., when maximum gain other maximum attenuator, vice versa. They never both both off. Their main purpose control transmit receive paths provide half-duplx operation required speaker-phone. attenuators controlled solely voltage pin(pin 25).The voltage provided attenuator control block,
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
which receives inputs: Rx-Tx comparator, transmit detector comparator, c)the volume control. response attenuators based difference voltage from VCC, therefore simple method monitoring circuit operation monitor this voltage difference(referred Vacf).If Vacf approximately millivolts circuit receive mode. Vacf approximately millivolts circuit idle mode, attenuators gain setting approximately half way(in between their fully fully positions. maximum gain attenuation values determined three resistors RR,RTX,RRX(referred Fig2,3,4).RR affects both attenuators according value RELATIVE RRX, which indicates variations versus ratio other resistors RR.(GRX maximum gains, maximum attenuations).RTX affects gain attentuator according 3.As seen from figures, gain difference(from off) reasonably constant 45dB until upper gain limit approached. value recommended starting point, then selected suit particular design goals. input impedance attenuators RXI) typically 5.0k ohms, maximum input signal which will cause output distortion 250mVrms(707mVp-p).The 4300 ohms resistor 0.01µCapacitor RXO(in 1)filters high frequency components receive path. This helps minimize high frequency acoustic feedback problems which occur filter were present. filter's insertion loss 1.5dB 1.0kHz.The outputs attenuators inverted from their inputs. Referring attenuator control block, Vacf voltage output determined three inputs. relationship inputs outputs summarized following truth table.
TX-RX COMP
TRANSMIT COMP
VOLUME CONTROL
VACF
MODE
Transmit Transmit Effect 6.0mV Transmit Transmit Idle Effect 75mV Idle Affects Vacf Receive Transmit 50-150mV Receive Affects Vacf Receive Idle 50-50mV Receive seen from truth table, Tx-Rx comparator dominates. transmit detector comparator effective only receive mode. Tx-Rx comparator transmit position when there sufficient transmit signal present over above receive signal. transmit detector comparator then determined whether transmit signal result background noise(1 relatively stable signal),or speech which consists bursts.If signal background noise, attenuators will into idle mode(Vacf=75mV).If signal consists speech, attenuator will switched transmit mode(Vacf=6.0mV).A further explanation this function will found section transmit detector circuit. Rx-Tx Comparator receive position when there sufficient receive signal overcome background noise speech signals. Vacf voltage will 150mV volume control maximum position, i.e. VLC(pin 24)=VB. less than gain receive attenuator, will vary complementary manner shown 5.It seen that minimum recommended operating level(VLC=0.55VB) gain transmit atternuator actually greater than that receive attenuator. effect varying vary Vacf, with resulting variation gains attenuators, shows gain variation with Vacf. capacitor ACF(pin smoothes transition between operating modes. This keeps down "clicks" speaker transmit signal when voltage switches. gain separation attenuators reduced from typical 45dB adding resistor between 20(VCC) 25(ACF).The effect reduction maximum Vacf voltage receive mode, while affecting Vacf transmit mode. example, adding ohms resistor will reduce Vacf approximately 15mV(to 135mV).decrease gain receive attenuator approximately 5.0dB, increase gain transmit attenuator similar amount. circuit requires receive attenuator gain +6.0dB receive mode, must adjusted ohms) re-establish this value. This change will also increase receive attenuator gain transmit mode similar amount. resistor also require changing reset sensitivity thansmit level detector.
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
AMPLIFIERS(Transmit Receive level Detectors)
logs amps monitor levels tharsmit receive signal, tell Tx-Rx comparator which mode should effect. input signals applied amplifiers(at RLI) through coupling capacitors current limiting resistors. value these components determines sensitivity respective amplifiers ,and effect switching times between transmit receive modes. feedback elements amplifier back-to-back diodes which provide logarithmic gain curve, thus allowing operation over wide range signal levels. outputs amplifiers rectified, having quick rise time slow decay time. rise time determined external resistor capacitor, order fraction second. switching time fixed, depends relative values transmit receive signals, well these external components. indicates transfer characteristics amps, indicates transfer characteristics with respect input signal level TLI,RLI,TLO, approximately Tx-Rx comparator responds voltages RLO, which turn functions currents sourced RLI, respectively. offset comparator input desired, e.g. prevent noise from switching system, give preference either transmit receive channel, this achieved biasing appropriate input(TLI RLI).A resistor ground will cause current flow that input, thus forcing output that amplifier biased slightly higher than normal. This amplifier then becomes preferred system operation. Resistor values from 500k ohms recommended this purpose.
SPEAKER AMPLIFIER
speaker amplifier fixed gain 34dB(50V/V),and noninverting. input impedance nominally ohms long output signal below that required activate peak limiter. indicates typical output swing available SKO(pin 15).Since output current capability 100mA,the lower curve limited 5.0Volt swing. output impedance depends output signal level relatively long signal level near maximum limits. Vp-p output impedance less than ohms, 4.5Vp-p less than ohms. output short circuit protected approximately When amplifier over driven, peak limiter causes portion input signal shunted ground, order maintain constant output level. effect that gain reduction caused reduction input impedance SKI) value less than 2.0k ohms. capacitor 17(AGF) determines response time peak limiter circuit. When large input signal applied SKI, voltage AGC(pin will drop quickly current source applied external capacitor. When large input signal reduced, current source turned off, internal 110k ohms resistor discharges capacitor that voltage return toots normal value(1.9Vdc).The capacitor additionally stabilizes peak limiting feedback loop. there need mute speaker amplifier without disabling rest circuit, this accomplished connecting resistor from GND.A 100k ohms resistor will reduce gain 34dB (0dB from SKO), ohms resistor will reduce gain almost 50dB.
TRANSMIT DETECTOR CIRCUIT
transmit detector circuit, also known background noise monitor, distinguishes speech(which consists bursts) from background noise( relatively constant signal).It does this storing voltage level, representative average background noise, capacitor CP1(pin 11).The resistor capacitor this have time constant approximately second(in 1).The voltage applied inverting input transmit detector comparator. absence speech signal, noninverting input receiving same voltage level minus offset 36mV.In this condition, output transistor turned off, voltage XDC(pin will GND. Tx-Rx comparator transmit position, attenuators will idle mode(Vacf=75mV). When speech presented microphone, signal burst appearing reaches noninverting input transmit detector comparator before voltage inverting input change, causing output switch high, driving voltage approximately 4Volts.This high level causes attenuator control block switch attenuators from idle mode transmit mode(assuming Tx-Rx comparator transmit mode).As long speech continues arrive, maintained level above background, voltage will maintained high level, circuit will remain transmit mode. time constant
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
components will determine much time circuit requires return idle mode after cessation microphone speech signals, such occurs during normal pauses speech. series resistor capacitor XDI(pin determine sensitivity transmit detector circuit. indicates change voltage levels response steady state sine wave applied input 0.068µF capacitor 4700 ohms resistor( voltage change times greater than change P2).Increasing resistor, lowing capacitor, will reduce response these pins. first amplifier(between CP2) logarithmic order that this circuit able handle wide range signal levels(or other words, responds equally well people talk quietly people shout).Fig indicates transfer characteristic amp. indicates response Pins 11,12, varying signal microphone. series events follows: follows peaks speech signals, decays rate determined 10µA current source capacitor this pin. increases rate determined this after made positive transition. will follow decay pattern CP2. noninverting input transmit detector comparator follows CP2, gained 2.7, reduced offset 36mV.This voltage, compared CP1, determines output comparator. will rise quickly 4Vdc response positive transition CP2, will decay rate determined this pin. When above 3.25Vdc, circuit will transmit mode. decays towards GND, attenuators taken idle mode.
MICROPHONE AMPLIFIER
microphone amplifier noninverting, internal gain 34db(50V/V), nominal input impedance ohm. output impedance typically less than ohms. maximum voltage swing available output approximately more than what required most applications. input should coupled microphone upset bias voltage. Generally, microphone sensitivity adjusted varying microphone bias resistor, rather than attempting vary gain amplifier.
POWER SUPPLY
voltage supply MC34018 should range Volts, although circuit will operate down 4.0Volts>the voltage supplied either from RING, from separate supply. required supply current, with signal speaker, shown upper curve indicates normal operating current when logic "0".Fig indicates average current required when supplying various power levels ohms speaker. also indicates minimum supply voltage required provide indicated power levels. peak power supply current 5.0-5.0 volts occurs circuit comes into regulation. imperative that supply good stability reasons. this well filtered( 1000F capacitor IC), variation caused required speaker current flowing through this cause frequency oscillation. result usually that circuit will speaker signal rate hertz. Experiments have shown that only inches wire between capacitor physically adjacent equally imperative that both ground pins(pin have loss connection power supply ground.
regulated output voltage 5.4+-0.5 volts. Regulation will maintained long typically greater than regulated value VCC. milliamps sourced from this supply external use. output impedance less than ohms. 47µF capacitor indicated connection essential stability reasons, must located adjacent circuit deselected (see section chip select), voltage will volts.
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
MC34018 powered from regulated supply( Ring lines) less than volts, configuration used ensure that regulated<the regulated voltage applied both VCC, with held logic turn internal regulator( Chip Select function available when circuit used this manner).Fig indicates supply current used configuration, with signal speaker. When signal sent speaker, curves apply.
regulated output voltage with nominal value +-0.4volts.It derived from tracks holding value approximately VCC.1.5milliamps sourced from this supply typical output impedance ohms. 47µF capacitor indicated connection required stability reasons, must adjacent circuit deselected(see section Chip Select), voltage will Volts.
CHIP SELECT
allows chip powered down anytime functions required. logic level range 1.6V deselects chip resulting supply current shown 12.The input resistance greater than ohms. regulated voltage volts when chip deselected. Leaving open equivalent logic "0"(chip enabled).
SWITCH TIME
switch time speakerphone circuit depend only various external components, also operating condition circuit time change taken effect. example, switching time form idle transmit generally quicker than switching time from receive transmit(or transmit receive). components which most significantly affect timing between transmit receive modes those pins (transmit turn-on),6(transmit turn-off),7(receive turn -on),8(receive turn off).These four timing functions independent, interact since Tx-Rx comparator operates relative Tx-Rx comparison, rather than absolute value. components pins 11,12,13,23 affect timing from transmit mode idle mode. Timing from idle mode transmit mode relatively quick(due quick charging various capacitors),and greatly affected component values. affect idle transmit timing since Tx-Rx comparator must already transmit mode this occur. following table provides summary effect switching time various components, including volume control:
COMPONENTS
RC@pin5 RC@pin6 RC@pin7 RC@pin8 RC@pin11 C@pin12 RC@pin13 RC@pin23 V@pin24 C@pin25
Moderate Significant Significant Moderate effect effect effect effect effect Moderate
Significant Moderate Moderate Significant Slight Slight Slight Slight Moderate Moderate
IDLE
effect effect effect effect Moderate Significant Slight Significant effect Slight
Additionally ,the following should noted: have dual function that they affect sensitivity respective amplifiers, other words, loud speech must order gain control speaker phone circuits. also dual function that determines sensitivity transmit detector circuit. volume control affects switching speed, relative response transmit signals, following manner: when circuit receive mode, reducing volume control setting increases signal TXO, consequently signal pin. Therefore given signal will switch circuit into transmit mode quicker volume settings. above mentioned times will change significantly varying amplitude input signals, well
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
varying external components.
APPLICATIONS INFORMATION
MC34018 speakerphone designed provide function additionally required when speakerphone added standard telephone. provides necessary relative level detection comparison speech signals provided talkers speakerphone(near speaker) distant telephone(far speaker). MC34018 designed with electorate type microphone ohms speaker, output power capability 100mW.All external components surrounding this device passive, however, this does require additional circuitry interface Ring telephone lines. suggested circuits shown data sheet. depicts configuration which does include handset, dialer, ringer. only controls S1(to make connection line),S2(a "privacy" switch),and volume control. meant used parallel with normal telephone which dialing ringing functions. depicts means providing logic level signal that indicate which mode operation MC34018 Comparator indicates whether circuit receive transmit mode comparator indicates(when transmit/idle mode) whether circuit transmit idle mode. LM393 dual comparator chosen because current requirement (<1.0mA), voltage requirement 2.0volts), cost.
TRANSMIT OUTPUT
0.068 4.7k 100k 200k
line input
Receive input
1000
transmit detector comp
0.05
regulator
5.4V
(36mV) 3.3k 0.068
TRANSMIT RECEIVE/TRANSMIT COMP
Attenuator control
peak limiter
2.2M
Speaker
4.7k
transmit attenuator
receive attenuator
regulator
RECEIVE
0.068
2.2M
4.3k 0.05 0.01
Test circuit
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
Transmit attenuator versus
Receive attenuator versus
Gain Vacf=6.0mV
Gain Vacf=6.0mV
Attenuation Vacf=150mV
Usable range Attenuation Vacf=150mV
RR=30k ohms VLC=VB
RR=30k ohms VLC=VB
100k
100k
(ohms)
(ohms)
Gain attenuation versus Resisrtor Ratio
RRX/RR Vacf=150mV RTX/RR Vacf=6.0mV
Attenuation Gain versus
RRX=18k ohms RTX=91k ohms RR=30k ohms
RRX/RR Vacf=6.0mV
RTX/RR Vacf=150mV
Circuit receive mode
VLC=VB Mimimum recommended level
Ratio
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
Attenuator Gain Vacf
Transfer Characteristics
Output Channel(mV)
Input Current (RLI,TLI,XDI)
RR=30k ohms RTX=91k ohms RRX=18k ohms
Output Voltage (RLO,TLO,CP2)
Vacf(mV)
Input Current(
Transfer Characteristics
R=2700 ohms C=0.1 10.0
Speaker Output Supply Voltage
VSKO MAX(p-p Volts)
Output Channel(mV)
R=4700 ohms C=0.068
load
R=4700 ohms C=0.068 (RLI,TLI) Input Votage 1.0kHz) (RLO,TLO)
ohms load
10.0 11.0
Input Voltage(mVp-p)
V+(Volts)
Transmit Detector operation
Input Signal MCI)
CP2(pin
V1=200mV
Solid line=CP1(pin11) Dotted line=Voninverting Input transmit detectot Comparator
Slope=0.5V/sec
36mV
XDC(pin
Volts
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
Response
Supply Current Supply Voltage
DVCP1 CP1,CP2 Voltage Channel(mV)
CS=0
IV+(mA)
VSKO=0mVrms
DVCP2
CS=1
VMCO(mVrms)
V+(Volts)
Supply Current Supply Voltage Speaker Power
100mW
Supply Current Supply Voltage
80mW
Available operating Range
IV+(mA)
Is(mA)
50mW
20mW
10mW
V+(Volts)
Vs(Volts)
Alternate Power supply Configuration
MC34018
(Regulated Supply)
UNISONIC TECHNOLOGIES
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QW-R108-006,A
MC34018 LINEAR INTEGRATED CIRCUIT
0.01 4.7k 220k 2.7k 0.05
Hook Switch
470k
0.01
4700pF 4700pF 8.2k 1000 6.8k 8.2k 8.2k 470k 2.2k 0.068
470k
0.01
0.01 3.3k 100k 3.3k 0.068
0.05
0.068
4.7k
0.068
MC34018
Speaker
4.3k
0.05
200k
2.2M
2.2M
Volume Control
basic Line powered Speakerphone
MC34018
0.01
Tx/Idle
Idle
Digital Transmit/Idle/Receive Indication
UNISONIC TECHNOLOGIES
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QW-R108-006,A
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