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Specifications and Applications Information


*****Page.1*****

(Telephone speech network with dialer interface)

The MC34114 is a monolithic integrated telephone speech 
network designed to replace the bulky magnetic hybrid 
circuit of a telephone set.

i_CA[EC^[tF[XɂdbXs[`Elbg[Nj
MC34114́AꂳꂽdbXs[`ł
傫ȎCnCubhɑ悤ɂȂĂlbg[N
db@̉HB



The MC34114 incorporates the necessary functions of transmit 
amplification, receive amplification, and sidetone control, each with 
externally adjustable gain. Loop length equalization varies the gains 
based on loop current. 



MC34114́AKvȋ@\܂
gAeXgiāA̓j󂯂Ă
OIɉB [v܂œ͂́Aς܂
[vɊÂ܂B





The microphone and receive amplifiers during
dialing.

}CŃAāAAv󂯂_C邱ƁB






 A regulated output voltage is provided for biasing of the 
microprocessor, or other circuitry. 



Ǘꂽo͓d́A΂点邽߂ɒ񋟂܂
}CNvZbT[܂͑̉HB





The MC34114 is designed to operate 
at a minimum of 1.2 volts,making party line operation possible.


MC34114́A悤ɐ݌vĂ܂
\Ȍ̍Œ1.2volts,makingŁB






 A circuit using the MC34114 can be made to comply with Bell Telephone, British
Telecom(BT), and NTT(Nippon Telegraph & Telephone)standards. 


MC34114gĂH́AxdbɑΉ邱Ƃ肦āApł肦܂
eR~jP[ViBTjNTTi{eOtTelephonejWB





It is available in
a standard 18-pin DIP, and a 20-pin SOIC(surface mount) package.


́Aŗpł܂BWI18-sDIP20-sSOICi\ʎjpbP[WB







EOperation Down to 1.2 Volts.

1.2 {g ܂ł 쓮 B




EExternally Adjustable Transmit, Receive, and Sidetone Gains

OI ߉\ M A  ܂AāA  





EDifferential Microphone Amplifier Input Minimizes RFI Susceptibility.

ʓI }CN EAv  ́ARFI  ŏɂ ܂B





ETransmit,Receive,and Sidetone Equalization on Both Voice and DTMF Signals

 DTMF M  Transmit,Receive,and  





ERegulated 1.7 Volts Output for Biasing Microphone.

}CN ΂点 ߂ Ǘꂽ 1.7 {g o B








ERegurated 3.3 Volts Output for Powering External Dialer or MPU.


3.3 {g O _CA[ ܂ MPU 𓮂 ߂ o͂ Regurated B






EMicrophone and Receive Amplifiers Muted During Dialing


}CN ́AāA _C Ƃ̊ԁA  Av 󂯂






EDifferential Receive Amplifiers Output for Powering External Dialer or MPU

́AAv o O _CA[ ܂ MPU 𓮂 Ƃ  ܂





EOperates with Receiver Impedances of 50 Ohms and Higher

50 I[  V[o[ ECs[_X  AāA 荂  ܂






EComplies with NTT, Bell Telephone and BT Standards

NTT A x db  BT W  ]܂







*****Page.2*****



VCC	:   	Power supply pin for the IC. 

		IĈ߂̓d͋s B

		Supply voltage is derived from loop current.

		d́A[vɗR܂B

		Transmit amp output operates on  this pin.

		o͂̃s̏œAv𑗂ĂB



LR	:	Resistors R2 + R3 at this pin set the DC characteristics

		̃s + R3 DCɉۂ Resistors R2



VB	:	A resistor or appropriate network(R1) connected from this pin to VCC sets the AC terminating impedance (return loss spec).

		̃sVCC ܂ Ȃ A WX^[ ܂ K؂ lbg[N i R1 j ́ACs[_X i ˌ XybN j IĂ AC Zbg ܂B




VR	:	A 1.7 volt regulated output which can be used to bias the microphone.

		A 1.7 {g̓}CN ΂点 ̂ɗp邱Ƃło͂Ǘ܂ B


		Additionally, this voltage powers aportion of the internal circuitry.

		ɁA̓d͓Haportion𓮂܂B

		Can nominally supply 300-500 uA.

		300-500 uA 𖼖ڏ  Ƃł ܂B



GND	:	Ground pin for the entire IC. 

		SĂ IC ̂߂ { s B


		Normally this is not connected to , nor to be confused with earth ground.

		ʏ A ͂Ȃ ܂ A܂A A[X   Ƃ͔҂܂ł B




MC1	:	Inverting differntial input to the microphone amplifier.

		}CN EAvւInverting differntial  B


		Input impedance is typically 20k

		̓Cs[_X́AʓI20kł





MC2	:	Non-inverting differntial input to the microphone amplifier.

		}CN EAv ւ Non tɂĂ differntial  B

		Input impedance is typically 20k

		̓Cs[_X́AʓI 20kł




MC0	:	Microphone amplifier output. 

		Microphone Av o B

		Amplifier's gain is fixed at 30dB.

		Av ̑ ́A30 dBŏ܂B





RAGC	:	Loop current sensing input. 

		 Ă Loop  B

		The voltage at this pin, determined by the loop current and R3,
		operates the loop length equalization circuit.


		̃si[vR3ő肳 j̓d
		[v ܂œ͂  T[Lbg Ǘ ܂B




TXI	:	Input to the transmit amplifier from the microphone amplifier, DTMF	source, and other sources.

		Input ߂  ܂}CN EAv  Av A DTMFsource AāA   B

		input impedance = 1.0k

		̓Cs[_X = 1.0k





RXO2	:	Receive amplifier non^inverting differntial output.

		Receive Av non^inverting differntialóB


		Current capability to the receiver is typically

		V[o[ւ̔\͂ʓIɂł 

		set at }3.0 mA peak.

		}3.0 mA s[N P ĂB






RXO1	:	Receive amplifier inverting differntial output. 

		differntial o tɂĂ Receive Av B


		Current capability to the receiver is typically } 3.0mA peak.

		V[o[ւ݂̌̔\͂́AʓI } 3.0 mA s[N łB



		Gain is set by R8.

		 ́AR8 ɂăZbg ܂B




RXI	:	Summing input to the receive amplifier.

		Summing ́A͂܂  ܂Av B


		This pin is an AC virtual ground.

		̃śAACznʂłB



RXA	:	Summed input to the receive amplifier, sidetone amplifier, and an AGC point.

		Summed ́A͂܂  ܂Av A  Av AāA AGC _ B


		Normally connected to the receive amplifier input (RXI) through a coupling capacitor.

		ʏȂ܂󂯂܂RfT ɂē͂i RXI j Av B



ZB	:	Input to the receive current amplifier. 

		Input ߂  ܂Jg Av B


		A balance network (ZB) is connected between this pin and VCC.

		oX Elbg[N i ZB j ́A s  VCC ̊ԂɂȂ܂B



		The network affects the receive level and sidetone performance.

		lbg[N ́Aeyڂ ܂ ܂x AāA ptH[}X B


		Input impedance is `500 in seris with a diode.

		̓Cs[_X ͂ł@_CI[h ɂ seris  ` 500 B






MS	:	Mode Select Input. 

		[hI΂ꂽ B



		A logic "1" sets the IC for pulse dialing. 

		_u1 v́AIC _CĂ   ݒ肵 ܂B



		A logic "0" sets the IC for tone(DTMF) dialing.

		_ u0 v́AIC _CĂ  i DTMF j  ݒ肵 ܂B



		Effective only if xMUTE is at a logic "0".

		xMUTE _ u0 v  ꍇ AʓI B



		Input impedance is `60k.

		̓Cs[_X́` 60kłB






xMUTE	:	xMute input. A logic "1" sets normal speech mode. 

		xMute  B _ u1 v́Aʏ Xs[` E[h Zbg ܂B


		A logic "0" mutes the microphone and receive amplifiers and allows MS to be functional.

		_ u0 v́A}CN ̉ ܂AāA Av  ܂AāA@\Ił MS  ܂B



		Input impedance is `60k referenced to VDD.An internal fixed delay of 11mSec
		minimizes clicks in the receiver when returning to  the speech mode.

		̓Cs[_X ́A60k 11mSec AVDD.An    x Ƀt@X `  
		Xs[` E[h  ߂ Ƃ AV[o[ ŃNbN ŏɂ܂B




VDD	:	A regulated 3.3 volt output for an external dialer. 

		A ́AO _CA[ ̂߂ 3.3 {g o Ǘ܂ B


		Output source current capability is  1.0mA in Speech mode, 2.5mA in tone dialing mode.

		o \[X  \ ́ASpeech [h  1.0 mA  A_C [h  2.5 mA B







*****Page.10***********

(FU8NCTIONAL DESCRIPTION)

(INTRODUCTION)

The MC34114 is a speech network which provides the hybrid function and the DC loop current interface of a telephone, and is  meant to 
connect to Tip and Ring through a polarity guard bridge.

MC34114 ́A^ @\  DC db  ݂ C^[tF[X [vƁA߂ Xs[` Elbg[N  AāA Ӗ

Tip  Ȃ ĂAāA ɐ ʂĂ Ring ̓ubW ܂B





The transmit, receive, and sidetone gains are externally adjustable, and additionally,
line length compensation varies the gains with variations in loop current.

 ܂A  ĂAāA āA ̏ A  ͊OI ߉\ł

܂ł̒ ⏞ ́A[v  ɂ ω  Aς܂B




The microphone amplifier employs adirrerntial input to  minimize RFI susceptibility.


}CN EAv ́ARFI  ŏɂ ߂ɁAadirrerntial  gp܂B




 The loop current interface portion determines the dc voltage versus current characteristics, and provides the required regulated 
voltages for internal and external use.


[v  C^[tF[X  ́Ad  ݂  肵 A K{ Ǘꂽ d O gp  񋟂 ܂B




 The dialer interface provides three modes of operation: speech(non-dialing),pulse dialing and tone(DTMF) dialing.

_CA[ EC^[tF[X ́A쓮  3 @ 񋟂 ܂F
_CĂ Xs[` i  _CĂ j ,pulse  _CĂ  i DTMF j B



When switching among the modes, some parameters are changed in order to optimize the circuit operation for that mode. 

[h ̊Ԃ ς Ƃ A኱ p[^ ͂ [h ̂߂ H 쓮 œK ߂ɕς ܂B


The following table summarizes those changes:

ȉ e[u ́A ω ܂Ƃ ܂F








(DC LINE INTERFACE AND LINE LENGTH COMPENSATION)

iDC  C^[tF[X   ܂ł̒ ⏞ j


The DC line interface circuit(Pins 1,2,3)sets the DC coltage characteristics with respect to  loop current. 

DC  C^[tF[X H i s 1,2,3 j ́A[v  Ɋւ DC  W  Zbg ܂B



See Figure 22.

}22  ĂB





The DC voltage at VCC is determined by the level shift from VCC to LR, plus the voltage across R2 and R3. 

R2  R3 ̒ d vX AVCC  d ́AVCC  LR ܂ x EVtg  肳 ܂B




ICC is the internal bias current required by the MC34114,nominally in the range of 10 mA.

ICC ́A10 mA  ͈  MC34114,nominally ɂ KvƂ  oCAXd  B




ICC can be reduced, if necessary, by increasing R12, consistent with the transmit and receive signal requirements (see the Transmit Path section). 

ICC ́AKvɉ AR12 𑝂₷ Ƃɂ 炳 Ƃł ܂BāAM M  i Transmit Path   ܂j  vĂ ܂B



See Figures 2-4, 8 and 9.

}2-4 A 8  9  ĂB




 In the speech and pulse dialing modes current source is off. 

[h Ƀ_CĂ Xs[`   ɂ Ad ̓Itł B



and the level shift is due to Q1's base-emitter drop(`1.4V),1.0 volt across the 20k resistor, and the voltage across R1, which varies with VCC from 0.15 volts to `1.0 volt.


āA x EVtg ́AQ1 ̃x[X - G~b^ ቺ ɂ  ܂ai ` 1.4 V j ,1.0 {g 20 k WX^[  R1 i0.15 {g  ` ܂ VCC ɂ 1.0 {g قȂ ܂j̒ d ̌ B



When the loop current coming in from Tip and Ring exceeds the ICC requrement, the excess current flows through Q1, R2 and
R3, to set the slope of the V-1 characteristic for the circuit(Q1 has an equivalent resistance of `10).


Tip  Ring  Ă [v  ICC requrement  Ƃ AH i Q1 ɂ́` 10   R  ܂j ̂߂ Ɠ uP  X ݒ肷 ߂ɁAߏ  Q1 A R2  R3 ̒  ܂B



See Figure 10.


}10ĂB




In the tone dialing mode, current source l1 is on,drawing an additional 1.7mA through R1, increasing the level shift by `1.0 volts(for R1 = 600).

_C [h  A d l1 ́Aon,drawing  Ax EVtg 1.0 {g i R1 = 600 ̂߂ j ` ₵ AR1 ʂ  1.7 mA B




This feature ensures that, at low loop currents, sufficient voltage is present at VCC for the DTMF signals,and that the VDD regulator supplies sufficient voltage to an external dialer.

VDD č@ O _CA[  \ d  DTMF signals,and ̂߂ A\ d VCC  ݂ ƂA  ́AႢ [v   AmƂ ܂B




The ICC current increases by `1.3mA in this mode.

ICC  ́A [h  ` 1.3 mA ɂ  ܂B



 R1 must be kept in the range of 100 to 1800. 

R1 ́A1800 ܂ 100  ͈  ۂ Ȃ΂Ȃ܂ B




If it is too large, insufficient current will flow into VB to bias up the circuit.

ꂪ܂ 傫 Ȃ As\ ͉H̏ ΂  VB  ꍞ ܂B






If it is too small, insufficient filtering at VB will result unless C1 is increased accordingly.

 ܂  Ȃ AC1 ɉ ₳ Ȃ AVB  s\ tB^O ͋N ܂B



Speech signals must be well filtered from VB.

M ́AVB  悭 tB^[ɒʂ Ȃ΂Ȃ܂ B



 The voltage across R3 determines the operation of the AGC circuit (line length compensation).

R3 ̒ d ́AAGCH i  ܂ł̒ ⏞ j   肵 ܂B




As the voltage at RAGC increases from `0.4 volts to `1.2 volts, the AGC Control varies the current gain of the two AGC points(Figure 1) from 1.0 to 0.5, thereby reducing the gain of 
the transmit and receive paths by 6.0 dB.


RAGC  d ` 0.4 {g  ` 1.2 {g ܂  AAGC Control 1.0  0.5 ܂ 2AGC_i }1 ǰ݂̊l ς ܂BāAɂ6.0dBMoH̊l炵 ܂B



See Figure 7.Pin 9 is a high impedance input.

}7.Pin 9 ͂  Cs[_X ł Ƃm ĂB




 The values of R2 and R3 can be varied as required to comply with various regulatory agencies, to compensate for
additional circuitry powered by the loop current(microprocessor,etc), or to change the starting point of the AGC dunction.


낢 ē@  Ή A [v d i microprocessor,etc j   Ȃ H  ⏞ A AGC dunction  o_ ς ߂ɁAR2  R3  l ́AKvɉ ω Ƃł ܂B





If the AGC is not used, Pin 9 should be connected to ground for high gains, or to VR for low gains.


AGC g Ȃ Ȃ APin 9 ͍     A ܂́A Ⴂ  ̂߂ VR  ڑĂȂ΂Ȃ܂ B




***********Page.11****************

(VOLTAGE REGULATORS)
 The MC34114 has two internal voltage regulators which are used to power external as well as internal circuitry.






 The VR regulator provides 1.7 volts at a maximum current of 500 uA(see Figure 5). This output is normally used to set
the DC bias into TXI (Pin 10), and  to bias the electret microphone. VR will typically be `300 mV less than VCC
when VCC is below 2.0 volts.

 The VDD regulator provides 3.3 volts at a maximum of 1.0 mA in the speech mode, and 2.5mA in the pulse or tone dialing modes
(see figure 6). It is normally used to power an external dialer,and other associated circuitry. VDD is normally@`0.5 volts less
than VCC until VDDregulates. It is a shunt type regurator which automatically switches to a high impedance mode when VCC falls 
below 1.4 volts.This feature prevents excessive battery drain in the exent a memory sustaining battery is used with the external dialer.
Leakage current(with VCC = 0) is typically 0.02uA with an applied voltage of up to 6.0 volts at VDD, with pin 17 open or at VDD.

If Pin 17 is at ground, a current of several hundred microamps will flow into VDD and out of pin 17(see paragraph on Logic Interface).


(MICROPHONE AMPLIFIER)
 The microphone amplifier (Pins 6,7,8) has a differential input, single ended output, and a fixed internal gain of +30 dB (31.1V/V).
The output is in phase with MC2, and out of phase with MC1. The inputs(see Figure 23) have a nominal impedance of 20 k, and are 
matched to provide a high common mode rejection (typically 26 dB).

To preserve a high CMRR against unwanted signals induced in the microphone leads, the microphone should be biased with two equal value
resistors as shown in Figure 1.

 The output (MCO) has  a DC bias voltage of `1.1 volts(VCC > 3.0 volts), and can nominally swing `2.0 volts p-p (500 mV p-p at VCC = 1.2 volts).
The output impedance is `270, and has a peak current capability of `160uA for 5% THD.

 When the MC34114 is switched to either dialing mode, the microphone amplifier is muted by `70dB(300 Hz`4 kHz),effectively disabling the microphone.
The DC voltage at MCO is `80 mV when muted.



(TRANSMIT PATH)
 The AC transmit path consists of the components shown in Figure 24 (taken from Figure 1).

The voltage output at MCO is converted to a current into TXI by C5, R6, and TXI's 1.0k input impedance(with a slight error due to R12).
A1 and A2 are current amplifiers with a combined gain of 100.The AGC point has a current gain of 1.0 at low loop currents, and
decreases to 0.5 as loop current increases. Therefore the current gain from TXI to VCC varies from 100 to 50 as loop current is 
increased. The resulting current output at VCC acts on R1 and the line impedance (nominally 600 each, C1 is an AC short) to generate a 
voltage signal at VCC, and consequently, at Tip and Ring. The voltage gain from MC1-MC2 to Tip and Ring is therefore(first order)




*******Page.12*********


where Am is the gain of the microphone amplifier(31.1V/V). At low loop currents GTX@`84 V/V(38.5 dB),and decreases to `42 V/V(32.5 dB)
at higher loop currents, for the component values shown in Figure1 (@ 1.0kHz),
 For more precise calculations, consideration should be given to the effects of C5(in series with R6),R12 and R7 (each in parallel with TXI's
1.0k impedance),and C10 and the ZB network(each in parallel with R1 and ZLINE).The cumulative effects of these additional components is 
`1.5 dB.

 The voltage signal at VCC is out of phase with that at TXI, and in phase with that at MC1.
 The maximum avilable voltage swing at VCC is a function of the impedance at VCC (R1//ZLINE),the DC bias current at A2's output, and the 
VCC DC voltage. A2's bias current is determined by the bias current through R12 (VR/{R12 + 1.0k}) which is gained up by A1, A2 and the AGC point.
Figure 8 indicates the maximum voltage swing at VCC (with 5% THD).



(RECIVE PATH)
 The AC receive path consists of the components,
shown in Figure 25 (taken from Figure 1).
 R1, typically 600, provides the AC termination (return loss) for the receive signals coming in on Tip and Ring (C1 is an AC short).
The receive signal creates an AC current through the ZB network and the 500 resistor at the ZB pin.

A4 reduces that current by 1/2, and then feeds it through the AGC point which has a gain of 1.0 at low loop currents.
The AGC gain is reduced to 0.5 as loop current increases. The AC current out of the AGC point feeds through C8 to RXI, 
the receive amp's summing node (If C8 is large, RXA can be considered a virtual ground, and no AC current flows
through the internal 10k resistor).
The voltage swing at RXO1 is then determined by the current through C8 and the R8 feedback resistor.


The second op amp (at RXO2) is internally configured for inverting unity gain. The voltage gain from Tip and Ring to RXO1-RXO2
(differential) is  (first order).


where ZB = R10 + R9/C9 (`R10 + R9).
 For more precise calculations, the effects of C9 and C8 must be considered. C9 provides a phase shift to aid sidetone cancellation
(see paragraph on Sidetone), and C8 can be selected to provide low frequency roll-off.
High Frequency roll-off can be obtained by adding a feedback capacitor across R8.



For the component values shown in Figure 1, the receive gain measured `0.495V/V(-6.1dB) at low loop currents, and  reduces to `0.25V/V(-12dB
)at higher loop currents(@ 1.0kHz).

 When the MC34114 is switched to either dialing mode (xMute = low), the receive gain is muted by the switching in of the internal feedbak
resistor(RFINT from RXO1 to RXI)- typically 1.0k. The effective feedback resistor for the amplifier is now the parallel combination of R8
and RFINT. The amount of muting (in dB) can be calculated from:

The internal resistor is switched in coincident  with xMute(Pin 17) switching low. However, when xMute is switched high, a delay
(nominally 11 mSec) occurs before the internal resistor is switched out. This feature prevents dialing transients (Particularly
 during pulse dialing) from being heard as loud clicks in the receiver.

 The DC bias voltages at RXI, RXO1 and RXO2 is `0.65 volts. The bias current at RXI is `50 nA into the pin.
The maximum voltage swing at RXO1 and RXO2 is a function of the receiver impedance (typically 100- 150),and the value of the two
Irx current sources in Figure 25. Irx, set by R12 (between VR and TXI), is equal to:



Figure 9 indicates the maximum valtage swing available to the receiver.




*******Page 13********

(SIDETONE CANCELLATION)
 Sidetone cancellation is provided by current amplifier A3(see Figure 1) which generates a current representative of the transmit
signal to cancel the reflected sidetone signal coming in through ZB and A4. To achieve perfect cancellation (no AC current out of RXA),
it is necessary that:





where ZB is the network composed of R9,R10 and  C9 and ZLINE is the AC impedance of the line.The reactive components of the line's impedance
 can be compensated for by making the ZB network comparably reactive. In Figure 1, C9 provides a phase shift to compensate for the phase
shift created by the phone line.



(LOGIC INTERFACE (xMute and MS))

 The two logic inputs (xMute and MS) are used to switch the MC34114 between the speech and dialing modes according to the following table.


Table 2, together with Table 1, describes the condition of the MC34114 in the various modes. Figure 26 shows the input configuration
for the xMute and MS pins.




 The xMute input has a nominal input impedance of 60 k, referenced to VDD. This pin may be left open for a logic "1" or connected to 
VDD. A logic "1" is defined as between VDD-0.5 volts and VDD. A logic "0" is defined as between ground and 1.0 volt. The switching
 threshold is `2.3 volts. When xMute is switched low (speech to dialing), the changes listed in Table 1 will occur within 10us.
Upon switching high (back to speech mode),however , the receive amplifier feedback resistor will be switched out after a delay
of (typically) 11ms. This feature prevents dialing transients (particularly during pulse dialing) from being heard as loud clicks in
the receiver. The other functions listed in Table 1 transfer within 10us.

 The MS pin is functional only when xMute is low and its only function is to provide an additional voltage level shift between VCC
and LR in the tone dialing mode (see the section on DC Interface). The input impedance is `60 k when VCC > 1.5 volts. A logic
"0" is between ground and 0.3 volts, and a logic "1" is between 2.0 volts and VDD. The switching 







