Speech circuit with dialler interface, regulated supply earpiece volum

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Speech circuit with dialler interface, regulated supply earpiece volum

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Application TEA1111A
Speech circuit with dialler interface, regulated supply earpiece volume control
AN99036
Philips Semiconductors
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Abstract
TEA1111A bipolar transmission circuit telephone sets. part TEA111x family. detailed description circuit blocks TEA1111A advices adjustments contained this report.
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Application TEA1111A
Speech circuit with dialler interface, regulated supply earpiece volume control
AN99036
Authors: Gauthier, Jaudard, Malaurie
Keywords Telecom Demoboard TEA1111A Microphone DTMF Earpiece
Date: June 9th, 1999
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Summary
detailed description blocks TEA1111A given. possible settings adjust transmission characteristics explained. TEA1111A incorporates microphone amplifier, DTMF amplifier, earpiece amplifier with step digital volume control control output. provides supplies peripherals including 3.25 regulated one. evaluation board OM5889 TEA1111A available.
Note: information presented this document does form part quotation contract, believed accurate reliable changed without notice. liability will accepted publisher consequence use. Publication thereof does convey imply licence under patent other industrial property rights.
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
CONTENTS
INTRODUCTION BLOCK DIAGRAM PINNING DESCRIPTION TEA1111A characteristics supply block 3.1.1 characteristics 3.1.2 Supplies peripherals control output impedance Microphone amplifier Earpiece amplifier block Automatic gain control. DTMF amplifier "MUTE" function. Anti-sidetone network. 3.9.1 TEA111x family bridge 3.9.2 Wheatstone bridge APPLICATION COOKBOOK. EXAMPLE APPLICATION. ELECTROMAGNETIC COMPATIBILITY. REFERENCES
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
LIST FIGURES Fig. TEA1111A block diagram Fig. TEA1111A pinning Fig. Basic application measurements Fig. characteristics configuration Fig. versus Fig. Main voltages versus line current. Fig. voltage behavior line powered condition. Fig. Influence resistor between SLPE between Fig. Influence Rslpe characteristics. Fig. Supply configuration Fig. Current consumption Fig. LEDC output current versus line current Fig. Equivalent impedance. Fig. Microphone channel Fig. Microphone gain versus frequency: influence temperature. Fig. Distortion line versus line signal TEA1111A Fig. Microphone noise versus line current. Fig. Common mode rejection ratio microphone Fig. Receive channel. Fig. Receive gains versus frequency: influence temperature. Fig. Distortion versus input signal Fig. Distortion versus load Fig. Noise Fig. microphone gain versus line current Ragc Fig. DTMF channel TEA1111A Fig. DTMF gains versus frequency: influence temperature Fig. Distortion DTMF signal line versus input signal Fig. MUTE/ input current versus MUTE/ input voltage Fig. Microphone gain reduction versus MUTE input voltage. Fig. Wheatstone bridge (left) TEA111x family anti-sidetone bridge (right). Fig. Equivalent average line impedance. Fig. Basic application TEA1111A. Fig. Component placement diagram demoboard.
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
INTRODUCTION
TEA1111A offers microphone, receive line interface functions required telephone sets. performs interface between line transducers handset. TEA1111A includes also DTMF amplifier dialling. selection between microphone amplifier DTMF amplifier made with "MUTE" function. MUTE/ input switches-off both microphone receive amplifiers switches-on DTMF amplifier. step digital volume control available earpiece amplifier. TEA1111A provides control output Furthermore, regulated 3.25 supply provided dialler microcontroller. report divided into parts: first part, chapter gives detailed description different circuit blocks TEA1111A including operating principles, settings transmission characteristics performances different functions; second part describes consecutive steps design adjust applications using TEA1111A introduces demoboard.
Note: values parameters given this application note accurate possible, please, refer last product specification final ones.
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
BLOCK DIAGRAM PINNING
Fig. shows block diagram TEA1111A, pinning shown fig.
Volume control MUTE/ current voltage reference
DTMF
regulator MIC+ MICV
circuit
voltage circuit control
LEDC
SLPE
Fig. TEA1111A block diagram
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
SLPE DTMF MUTE/
TEA1111A
LEDC MICMIC+
Fig. TEA1111A pinning TEA1111A NAME SLPE DTMF MUTE/ MIC+ MICLEDC DESCRIPTION Positive line terminal Slope adjustment Line voltage regulator decoupling Receive amplifier input Automatic gain control DTMF input Regulated supply peripherals MUTE/ input Earpiece volume control input Negative line terminal Receive amplifier output Earpiece amplifier inverting input inverting microphone input Inverting microphone input control output Supply voltage internal circuit
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
DESCRIPTION TEA1111A
curves shown this section result from measurement typical samples using schematic shown fig.
Cvcc Cvdd
Peripheral supply
MIC+ Rast1
Ctx2 Ctx1
MIC+
Cemc
MIC-
MIC-
TEA1111A
Rgar
Cgars
Ragc
Cgar
Cear
MUTE Rast2
3.92
MUTE/
LEDC DTMF SLPE
DTMF
Rast3 Rbal1 Cbal Rbal2
Rslpe
Creg
Fig. Basic application measurements
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
3.1.1
characteristics supply block characteristics
Principle operation TEA1111A generates stabilized voltage (called Vref) between pins SLPE. This reference voltage, typically temperature compensated. voltage used internal regulator generate stabilized Vref voltage decoupled capacitor Creg connected VEE. effective operation apparatus, TEA1111A must have resistance current high impedance speech signals. Creg capacitor, converted into equivalent inductance (see "set impedance" section), realizes this impedance conversion from value (Rslpe) value (Rcc +Rz//Cz audio frequency range). voltage SLPE proportional line current with offset supply currents (Isup Icc). This general configuration shown fig.
Isup from preamp Rgasint
internal circuitry
Rline Iline Rexch
Cvcc
regulator
Vexch
SLPE Islpe Rslpe
Cvdd
Creg
Fig. characteristics configuration regulates line voltage between pins SLPE. voltage calculated Vref Rslpe Islpe Islpe Iline Isup Iline line current current consumption
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
supply current peripherals connected Isup Current consumed between regulator line current Iline flowing into apparatus determined exchange supply voltage Vexch, feeding bridge resistance Rexch, resistance telephone line Rline voltage across telephone including diode bridge. Below threshold line current (typically equal internal reference voltage (generating Vref) automatically adjusted lower value (down absolute minimum voltage 1.45 This means that more sets operate parallel that very voltage feeding bridge line current higher value. line currents below this threshold current, TEA1111A reduced sending receiving performances, moreover value current Isup reduced. This called voltage area. internal circuitry TEA1111A supplied from VCC. line powered application, this voltage derived from line voltage means resistor (Rcc) must decoupled capacitor (Cvcc). Fig. shows current consumption (Icc) function supply voltage different conditions.
2,5E-3
2,0E-3
1,5E-3
1,0E-3
500,0E-6
000,0E+0 VCI=VDD open Iline=0
Fig. versus
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Fig. shows main voltages function line current.
Various voltages 000,E+0 20,E-3
VREF
40,E-3
60,E-3
80,E-3
100,E-3
120,E-3
VREF
140,E-3 Iline
Fig. Main voltages versus line current Fig. shows behavior voltage area line powered condition.
Various voltages
000,E+0 2,E-3 4,E-3
6,E-3
8,E-3
10,E-3
12,E-3
14,E-3
16,E-3
18,E-3 Iline
Fig. voltage behavior line powered condition
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Adjustments performances reference voltage, Vref, adjusted means external resistor Rva. increased connecting resistor between pins SLPE, decreased connecting resistor between pins (see fig. line powered application, using voltage reduction reduces peripheral earpiece amplifier supply capabilities: must least 0.35 higher than Vdd. ensure correct operation, advised adjust Vref value lower than higher than (the maximum operating voltage must guaranteed application well safe operating temperature). These adjustments will slightly affect parameters: there will small change temperature coefficient Vref slight increase spread this voltage reference matching between internal external resistors. Furthermore, resistor connected between will slightly affect apparatus impedance (see section "set impedance").
Vln(V)
10,0E-3 20,0E-3
RVA=inf
30,0E-3
40,0E-3
50,0E-3
60,0E-3
70,0E-3
80,0E-3
RVA=90K(LN-REG)
RVA=90K(REG-SLPE)
90,0E-3 Iln(A)
Fig. Influence resistor between SLPE between slope voltage influenced Rslpe resistor shown fig. value Rslpe slightly modified even preferred Changing this value will affect more than characteristics, also influences gains, characteristics, maximum output swing line voltage threshold Ith.
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Vln(V) 0,00E+00 2,00E-02 4,00E-02
Rslpe=15
6,00E-02
8,00E-02
Rslpe=20
1,00E-01
Rslpe=27
1,20E-01
1,40E-01
Rslpe=33
Rslpe=10
1,60E-01 Iln(A)
Fig. Influence Rslpe characteristics
3.1.2
Supplies peripherals
Fig. shows architecture supply block.
Isup
SENSE
Switch
Cvdd
Cvcc
Fig. Supply configuration
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Supply
Principle operation supply voltage normally used supply internal circuitry TEA1111A. However, small current drawn supply peripheral circuits having ground reference. supply voltage depends current consumed peripheral circuits shown following formula: VCC0 Rccint (Irec VCC0 Irec internal current necessary supply receive output amplifier realize peak voltage across earpiece impedance Irec Rccint internal equivalent impedance between Rccint output impedance voltage supply point. seen from fig.5, internal supply current depends voltage VCC, means that impedance internal circuitry connected between infinite. While supplying peripheral circuit VCC, supply current flowing through resistor decreases value voltage then reduces consumption. impedance combination with Irec Rccint which includes parallel impedance internal circuitry connected between VEE. line current equal equal this Rccint impedance approximately limited minimum value ensure correct operation, will limited maximum value. limit imposed requirement maintain minimum permitted voltage between SLPE which called Vmin. maximum current available depends settings Vref, Rcc(+Rz), Rslpe required signal level line receive outputs. simplify calculation, will worst case Rccint, which Rcc, gives: Irec Vref Rslpe Iline Irec Isup Irec VCCmin Vmin Rslpe Iline Irec Isup Ipmax VCCmin Ipmax Vref Vmin (Rcc Rslpe Irec Rslpe Vmin Rslpe Zline Adjustments performances impedance connected between also determines impedance, easiest increase current capability supply point increase reference voltage Vref connecting resistor between pins SLPE (see 3.1.1).
Supply
Principle operation 3.25 regulated supply dialler microcontroller. speech mode, line powered while trickle mode ringer mode externally powered.
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
When line powered, provide least when equals 3.25 value typically correlated with value line voltage follow: 3.65 0.35
3.25 Fig. show versus line current. correlation between line voltage done order voltage difference between least block diagram, transistors drive line current either VEE: when voltage higher than current driven VDD, when voltage lower than line current driven VEE, when voltage between both transistors conducting order minimize distortion. When equals 3.25 constant courant Isup (4.3 typically) sunk from This constant current doesn't affect return loss value taken into account characteristic. this condition, current available output least When lower than 3.25 both currents Isup reduced accordingly. trickle mode ringer mode, works shunt regulator 3.25 trickle mode current consumption shunt regulator dramatically reduced order have typically when lower than ringer mode, shunt regulator able sink between VEE. Fig. shows current consumptions VDD.
1,0E-9 10,0E-9 100,0E-9 1,0E-6 10,0E-6 100,0E-6 1,0E-3 10,0E-3 100,0E-3 Ivdd (mA)
Fig. Current consumption this supply structure, TEA1111A cannot used combination with TEA1081, TEA1083/A, TEA1085/A, TEA1093 OM5153. this configuration, stability possible.
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
control output
Principle operation TEA1111A provides on-hook off-hook status indication. This done current available LEDC that used simple buffer circuit drive LED. current flows between pins SLPE. line current condition, below current available LEDC. line currents between current LEDC (Iline 150. line currents larger than current LEDC output hardly increases.
Adjustments performances value current flowing also proportional gain buffer, demoboard, this gain (100 (100 this current should stay compatible with line current other current consumptions. this condition met, current flows into SLPE, characteristic modified distortion affected. Fig. shows LEDC output current versus line current.
Iled(A) 600,E-6
500,E-6
400,E-6
300,E-6
200,E-6
100,E-6
000,E+0 000,E+0 20,E-3 40,E-3 60,E-3 80,E-3 100,E-3 120,E-3 140,E-3 Iline
Fig. LEDC output current versus line current
impedance
Principle operation TEA1111A behaves like equivalent inductance that presents impedance (Rslpe) high impedance (Rp) speech signals. integrated resistance order 17.5 +/-15%. parallel with external realized Cvcc. Thus, audio frequency range, apparatus impedance (called impedance) mainly determined resistor. Fig. shows equivalent schematic impedance.
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Vref
Creg Rslpe internal resistor
SLPE
Rslpe
Creg
Cvcc
Fig. Equivalent impedance Adjustments performances When decreasing reference voltage Vref, resistor connected between parallel (see fig. slightly modifying impedance. complex impedance required, resistor replaced complex network (see fig. :Rcc Cz). resistance which influences value becomes
Microphone amplifier
Principle operation fig. block diagram microphone amplifier TEA1111A depicted.
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
from DTMF
MIC+ MICV
circuit
Rgasint
Rexch
SLPE Rslpe
Creg
Cvcc
Cexch
Fig. Microphone channel microphone amplifier symmetrical high input impedances (typically times between pins MIC+ MIC- with maximum tolerances 15%). input this microphone amplifier able handle signals mVrms with less than total harmonic distortion. seen from fig. microphone amplifier itself built parts: preamplifier which realizes voltage current conversion, end-amplifier which realizes current voltage conversion. overall gain Gv(mic-ln) microphone amplifier from inputs MIC+/MIC- output given following equation: Gv(mic-ln) Av(mic-ln) Av(mic-ln) (Rgasint Rrefint) (Ri//Zline Rslpe) with: apparatus impedance, Rcc//Rp (typically 17.5 Rgasint internal resistor realizing current voltage conversion (typically 29.5 with spread +/-15%) Rrefint internal resistor determining current internal current stabilizer (typically 7.25 with spread correlated spread Rgasint) Zline load impedance line during measurement gain control factor varying from Iline Iline when function applied (see chapter details) Using these typical values equation assuming Zline find gain equal
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Gv(mic-ln) Avtx
Iline
different gain controls (AGC; MUTE/) microphone preamplifier stage, modifying transconductance.
Adjustments performances shows typical frequency response gain microphone amplifier TEA1111A.
Gmic (dB) 44,9 44,7 44,5 44,3 44,1 43,9 43,7 43,5 43,3 43,1 42,9
|-25| |25| |75|
Frequency (Hz)
Fig. Microphone gain versus frequency: influence temperature shows distortion signal line function line signal
THD(%) Iline
[2-9]
Vln(Vrms)
15mA 75mA (Vrms)
Fig. Distortion line versus line signal TEA1111A
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Fig. shows microphone noise (psophometrically weighted: curve) versus line current nominal gain when resistor connected between inputs MIC+ MIC-.
Noise (dBmp) -76,2 -76,4 -76,6 -76,8 -77,2 -77,4 -77,6 -77,8 10,0E-3 20,0E-3 30,0E-3 40,0E-3 50,0E-3 60,0E-3 70,0E-3 80,0E-3 Iline
Fig. Microphone noise versus line current Fig. shows common mode rejection ratio curves present this fig. first spectrum signal when microphone signal applied MIC- while MIC+ shorted VEE, second spectrum signal when microphone signal applied pins MIC- MIC+ shorted together. Both signals kHz, difference between curves gives CMRR.
(dBm) -100 -110 1000 1500 2000 Frequency (Hz)
Fig. Common mode rejection ratio microphone
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Earpiece amplifier block
Principle operation fig. block diagram earpiece amplifier depicted.
MUTE/
DTMF
Volume control
Fig. Receive channel seen from fig. receive amplifier block built three parts: preamplifier which realizes voltage current conversion followed end-amplifier which realizes current voltage conversion volume control block that sets convertion gain preamplifier. preamplifier asymmetrical high input impedance between pins VEE. equal with maximum tolerance +/-15%. volume control provides steps gain with typical step amplitude 4.85 giving total typically 14.5 end-amplifier TEA1111A rail rail output structure drive loads down impedance output capability suitable several kind earpieces drive either dynamic, magnetic piezo-electric earpieces. case magnetic dynamic earpieces, capacitor series required decoupling. minimum gain setting, overall gain Gv(ir-qr) receive amplifier from input output given equation: Gv(ir-qr)min Av(ir-qr) Av(ir-qr)min 1.35 Rgarint/Rrefint with: Rgarint internal resistor realizing current voltage conversion (typically with spread +/-15%)
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Rrefint internal resistor determining current internal current stabilizer (typically 7.25 with spread correlated spread Rgarint) gain control factor varying from Iline Iline when function applied (see chapter details) Using these typical values equation, find gain equal Gv(ir-qr)min Av(ir-qr) 27.2 Iline
different gain controls (AGC; MUTE/) receive preamplifier stage, modifying transconductance. Adjustments performances gain earpiece amplifier externally reduced with resistor Rgar connected between pins however, this gain adjustment slightly increases gain spread affects temperature coefficient matching between internal external resistors. steps gain generated voltage decoding voltage control input VCI. gain versus voltage typically follow: 0.25 VDD: 0.27 0.54 VDD: 0.56 0.79 VDD: 0.82 VDD: Gmin (27.2 Gmin 4.85 Gmin Gmin 14.5 Gmax
external capacitors Cgar (connected between Cgars (connected between VEE) ensure stability earpiece amplifier when relationship Cgars Cgar fulfilled. capacitor Cgar provides first order pass filter, which cut-off frequency determined with Rgar Rgarint. Fig. shows frequency response typicall gains receive amplifier from different temperatures.
Gain(dB) 27,6 27,4 27,2 26,8 26,6 26,4 26,2
25°C -25°C
75°C
Frequency(Hz)
Fig. Receive gains versus frequency: influence temperature
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
maximum output swing depends line voltage, resistor, current consumption circuit, current consumption peripheral circuits load impedance receiving input handle signals mVrms with less than THD. Fig. shows distortion line current equal with gain setting minimum maximum this amplifier. Fig. shows distortion line current with loads.
[2-9] 0,005
0,01
0,015
0,02
0,025
0,03 0,035 Input level (Vrms)
Fig. Distortion versus input signal
[2-9]
load ohms load ohms
Output level (Vrms)
Fig. Distortion versus load
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Fig. shows noise loaded with (psophometrically weighted: curve) function line current different gains setting this amplifier. This curve been done with open input With antisidetone network connected input part microphone noise generated line will added.
Noise(dBVp) 10,0E-3
VCI=0
20,0E-3
30,0E-3
VCI=VDD3
40,0E-3
VCI=2VDD/3
50,0E-3
VCI=VDD
60,0E-3
70,0E-3 Iline
Fig. Noise
Automatic gain control
Principle operation TEA1111A performs automatic line loss compensation. automatic gain control varies gain microphone receive amplifiers accordance with line current. enable this function, must connected VEE. line currents below current threshold, Istart (typically mA), gain control factor equal giving maximum value gains Gv(mic-ln) Gv(ir-qr). this threshold current exceeded, gain control factor reduced then gains controlled microphone receive amplifiers also reduced. When line current reaches other threshold current, Istop (typically mA), gain control factor limited minimum value equal 0.5, giving lower value microphone receive controlled gains. gain control range both amplifiers typically which corresponds approximately line length (0.5 twisted pair copper) with attenuation dB/km. attenuation correlated current Iagc sunk AGC: when this current lower than typically gains maximum, when this current higher than typically gains minimum. This current proportional voltage between pins SLPE VEE. There internal resistor which sets Istart Istop, adding externally series (between pins VEE) reduces Iagc therefore increases values Istart Istop.
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Adjustments performances TEA1111A used with different exchange supply voltages different feeding bridge resistances. this purpose, resistor Ragc, inserted between pins VEE. This Ragc resistor increases both threshold currents Istart Istop proportionally. Fig. shows control microphone gain versus line current different values Ragc. When function required, must left open, then control factor equals both controlled gains their maximum values. When Ragc value Istart high, increasing value Rslpe reduces proportionally Istart shifts lower currents. this case, value Istop also reduced gains modified. value Rslpe increased lot, possible restore typical gains connecting parallel series network which makes total impedance
0,015 0,025 0,035 0,045 0,055 0,065 0,075 0,085 Iline
Fig. microphone gain versus line current Ragc
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
DTMF amplifier
principle operation fig.24, block diagram DTMF channel TEA1111A depicted.
MUTE/
from receive preamp
Volume control DTMF
from microphone preamp Rgasint
Rexch
SLPE
Cvcc Rslpe
Cexch
Fig. DTMF channel TEA1111A DTMF amplifier asymmetrical high input impedance between pins DTMF with maximum spread +/-15%. input biased VEE, when input DTMF signal polarized VEE, decoupling capacitor necessary. DTMF amplifier built parts: preamplifier which realizes voltage current conversion same end-amplifier microphone amplifier. applied DTMF channel. overall gain Gv(mf-ln) DTMF amplifier from input DTMF output given following equation: Gv(mf-ln) Av(mf-ln) Av(mf-ln) 0.244 (Rgasint Rrefint) (Ri//Zline Rslpe) with:
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
apparatus impedance, Rcc//Rp (typically 17.5 Rgasint internal resistor realizing current voltage conversion (typically 29.5 with spread +/-15%) Rrefint internal resistor determining current internal current stabilizer (typically 7.25 with spread correlated spread Rgasint) Zline load impedance line during measurement Using these typical values equation assuming Zline find gain equal Gv(mf-ln) Avmf 25.9 Furthermore, DTMF signal attenuated sent confidence tone with volume control providing steps gain with typical step amplitude giving total typically 14.2 Fig. shows frequency response DTMF amplifier different temperatures.
G(dtmf-ln) 26,5 26,3 26,1 25,9 25,7 25,5 25,3 25,1 24,9 24,7 24,5
|gain@25|
|gain@75| |gain@-25|
Frequency (Hz)
Fig. DTMF gains versus frequency: influence temperature input DTMF amplifier handle signals mVrms with less than THD. Fig. shows distortion line versus input signal Iline
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
[2-9]
0,02 0,04 0,06 0,08 0,12 0,14 Input level (Vrms)
Fig. Distortion DTMF signal line versus input signal
"MUTE" function
Principle operation "mute" realizes electronic switching between speech mode dialling mode. level applied MUTE/ input, both microphone receive channels disabled while DTMF channel enabled. applying high level leaving MUTE/ open microphone receive channels enabled while DTMF channel disabled. MUTE/ input pull-up structure VCC, directly driven open drain output. Nevertheless, case structure microcontroller side, push-pull output structure recommended polarize properly input microcontroller when varies current will flow from this pin). threshold voltage level 0.65 typically with temperature coefficient mV/°C. Fig. shows MUTE/ input current versus MUTE/ input voltage.
IMUTE 000,0E+0
-500,0E-9
-1,0E-6
-1,5E-6
-2,0E-6
-2,5E-6 VMUTE
Fig. MUTE/ input current versus MUTE/ input voltage
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Adjustments performances Fig. shows microphone amplifier gain reduction Iline input signal versus MUTE/ input voltage.
Gain (dB)
-100 0,50 0,60 Vmute 0,70
Fig. Microphone gain reduction versus MUTE input voltage "mute" function works down voltage equal about Below this threshold, microphone receive amplifiers remain always enabled independently MUTE/ input level. maximum voltage allowed MUTE/ input minimum GND-0.4
Anti-sidetone network
Principle operation avoid microphone signal come back with high level receive channel, anti-sidetone circuit uses microphone signal from SLPE (which opposite phase) cancel microphone signal input receive amplifier. anti-sidetone bridge already used TEA111x TEA106x) families conventional Wheatstone bridge shown fig. used design antisidetone network.
Zbal Rast1
Zline
Zline
Rast2
Rslpe SLPE
Rast1
Rslpe Rast3 SLPE Zbal
Fig. Wheatstone bridge (left) TEA111x family anti-sidetone bridge (right)
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
TEA111x TEA106x) family anti-sidetone bridge advantage relative flat transfer function audio frequency range output both with real complex impedances. Furthermore, attenuation bridge receive signal (between pins independent value chosen Zbal after impedance been fixed condition shown equation fulfilled. Therefore, readjustment overall receive gain necessary many cases. Compare previous one, Wheatstone bridge advantages needing resistor less smaller capacitor Zbal. disadvantages include dependence attenuation bridge value chosen Zbal frequency dependence that attenuation moreover, input stage introduce some distortion high level signal. This requires some readjustment overall receive gain.
3.9.1
TEA111x family bridge
anti-sidetone circuit composed Rcc//Zline, Rast1, Rast2, Rast3, Rslpe Zbal. Maximum compensation obtained when following conditions fulfilled: Rslpe Rast1 Rast2 Rast3 [Rast2 Rast3 Rslpe Rast1 Rslpe Zbal Zline scale factor chosen meet compatibility with standard value capacitor Zbal. practice, Zline varies strongly with line length line type. Consequently, value Zbal chosen with average line length giving acceptable sidetone suppression with short long lines. suppression further depends accuracy with which Zbal equals this average line impedance. Example Let's optimize theorical equivalent average line impedance shown Fig. 1265
Fig. Equivalent average line impedance compatibility capacitor value Zbal with standard capacitor value from series (220 nF): 0.636 Rast2, value 3.92 been chosen. using previous equations, calculate Zbal, Rast1, Rast3. find Rast1 Rast3 Zbal series with attenuation receive line signal between derived from following equation: Rast2 Rast1 Rast2 Rast2 Rast3 Zbal With values used this example, gives kHz. receive amplifier input impedance, typically
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
3.9.2
Wheatstone bridge
conditions optimum suppression given Zbal Rast1 Rslpe Zline) Also, this bridge type, value Zbal chosen that corresponds with average line length. attenuation received line signal between given Rast1 Zbal Rast1 used adjust bridge attenuation; value influence balance bridge.
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
APPLICATION COOKBOOK
this chapter, procedure making basic application given. Refering fig. design flow given number steps which should made. possible every step, components involved their influence every step given.
Step
setting
Adjustment
Adjust setting TEA1111A local requirements. Voltage LN-VEE This voltage adjusted changing Vref: increased with resistor between pins SLPE decreased down with resistor between LN).
slope
slope might modified changing value Rslpe (this advised: gains modified, characteristic modified).
Supply point
line powered applications, depends values Vref resistive part impedance network (Rcc Rz).
Artificial inductor
value adjusted changing value Creg: smaller value speeds-up current shape during transients decreases value inductance therefore affects frequencies.
Impedance sidetone After setting required impedance, sidetone optimized using antisidetone network order minimize loop gain line conditions. adjusted that step. Application impedance adjusted with impedance network connected between (Rcc Rz//Cz).
Sidetone
Adjust Zbal (Rbal1, Rbal2, Cbal) according line characteristics.
Internally defined, characteristics (Istart Istop) shifted higher line currents with external Ragc resistor connected between VEE. case necessary shift Istart Istop lower current values, value Rslpe must increased proportionally (see
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TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Step
Microphone gain
Adjustment
TEA1111A microphone receive gains microphone gain application adjusted before entering pins MIC+/MIC- TEA1111A. reduced using resistor Rtx3 which forms bridge attenuator with Rtx1 Rtx2. Ctx1, Ctx2 form high-pass filter with Rtx1, Rtx2 series with input impedance MIC+/MIC-. capacitor Cmic forms low-pass filter with impedance microphone resistors Rmicp/Rmicm.
Earpiece gain
gain between fixed 27.2 when increased steps 4.85 This gain also slightly reduced means resistor Rgar. input thresholds compatible with digital control digits R-2R network (VCIL, VCIH). capacitor Cgar parallel with Rgar forms low-pass filter, stability ensured with capacitor Cgars Cgar) between pins VEE.
TEA1111A DTMF gain DTMF DTMF selected with level MUTE/. level line must adjusted before entering DTMF. capacitor removed when input signal biased VEE.
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
EXAMPLE APPLICATION
demoboard (OM5889) available. TEA1111A used various applications, this demoboard includes only TEA1111A with basic environment. Fig. gives schematic demoboard while fig. gives component placement diagram. these schematics, capacitors connected with dotted lines indicated immunity purpose. According application, possible connect electret microphone instead VCC. this case, current capability would reduced electret consumption current capability would increased same value (which would allow slight increase earphone amplifier capability), moreover, electret microphone consumption would discharge capacitor CVDD.
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Rfeed
Cvcc
Cfeed
Rprot
Cvdd
Rmicp
MIC-
Ctx2
Rtx2
Rtx3
Cmic
MICP MICM
MIC+
Ctx1
Rtx1
Rmicm
Rast1
TEA1111A
Cgars
Rgar
Cgar
Cear
EAR+
Ragc
EAR-
Rcil
Rvil
Rvcih LEDC MUTE
VICH VICL MUTE/
Rvcil
Rast2
3.92
DTMF SLPE Rast3 Rbal1
Rslpe
Rvai
Creg
Rvad
Cbal
Rbal2
Fig. Basic application TEA1111A
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Fig. Component placement diagram demoboard
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
ELECTROMAGNETIC COMPATIBILITY
common international specification exists immunity, different assembly methods lead different solutions, only some advices provided. advisable take care impedance Ground, smallest always best. This means that Ground (VEE) trace must always large possible, best have second layer dedicated this purpose. MIC+/MIC- inputs also sensitive signals entering these pins would amplified). Care taken with lay-out microphone amplifier, which also helpful noise, providing good decoupling VEE. Capacitor hundred forming low-pass filters added input amplifier (C3, C4). impedance capacitors parallel with electrolythic between well parallel with Creg capacitor help. Usually impedance capacitor connected between (C12) helps conducted interferences, this capacitor parallel with impedance network apparatus, value must small enough. general when connections come from external environment (e.g. MICP, MICM, B,EAR+ demoboard), better filter signal before influences close environment TEA1111A (e.g. action C11, demoboard). When larger than small resistor between necessary stability.
very high frequencies parasitic inductance capacitors well length their connections about becomes major concern inhibit effect these capacitors, those frequencies, capacitors preferred.
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
REFERENCES
TEA1111A Speech circuit with dialler interface, regulated supply earpiece volume control Device specification TEA1111A Line Interface Demonstration Board User Manual OM5889 TEA1111A Line Interface Demonstration Board Philips Semiconductors Semiconductors Wired Telecom Systems Data Handbook -IC03a
Philips Semiconductors Semiconductors Wired Telecom Systems Application Handbook -IC03b
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
APPENDIX LIST ABBREVIATIONS DEFINITIONS
DTMF Gv(mf-ln) Gv(ir-qr) Gv(mic-ln) Iline Irec Islpe Istart Istop Isup MUTE/ OM5889 Rast Rexch Line terminals application example Automatic Gain Control: line loss compensation Balance Return Loss: matching between apparatus impedance reference Dual Tone Multi Frequency ElectroMagnetic Compatibility Earpiece amplifier gain adjustment TEA1111A DTMF amplifier gain Earpiece gain Microphone gain Integrated circuit Current consumption TEA1111A Current supply point Line current Current consumption peripherals Internal current consumption (from VCC) receive amplifier Receive amplifier input TEA1111A Part line current flowing through SLPE Start current function Stop current function Supply current voltage regulator Threshold current voltage part Scale factor anti-sidetone network Artificial inductor voltage stabilizer MUTE/ input TEA1111A Demoboard TEA1111A Earpiece amplifier output TEA1111A Resistor adjust sidetone bridge attenuation Antisidetone resistor Filter capacitor equivalent inductor connection TEA1111A Bridge resistance exchange Radio Frequency Interference
Philips Semiconductors
TEA1111A speech circuit with dialler interface, regulated supply earpiece volume control Application Note
Rgarint Rgasint SLPE MIC+/MICVCC Vref Vslpe Zbal
Internal resistance (123 which sets receive gain Internal resistance (29.5 which sets microphone gain Internal resistance between Voltage adjustment resistor Slope input TEA1111A Total Harmonic Distortion Microphone amplifier input pins TEA1111A Positive supply TEA1111A Regulated supply Ground reference TEA1111A voltage between Stabilized reference voltage between SLPE voltage level between SLPE Input impedance receive amplifier TEA1111A Anti-sidetone network balance impedance Gain control factor

Speech circuit with dialler interface, regulated supply earpiece volum

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