Philips TEA1098A Datasheet

INTEGRATED CIRCUITS

DATA SH EET

TEA1098A

Speech and handsfree IC

Preliminary speciﬁcation File under Integrated Circuits, IC03

2000 Mar 21

Philips Semiconductors Preliminary speciﬁcation

Speech and handsfree IC TEA1098A

FEATURES Line interface

• Low DC line voltage

• Voltage regulator with adjustable DC voltage

• Symmetrical high impedance inputs (70 kΩ) for

dynamic, magnetic or electret microphones

• DTMF input with confidence tone on earphone and/or loudspeaker

• Earphone amplifier for dynamic, magnetic or piezo-electric earpieces(with externally adjustable gain)

• Digital volume control on earphone amplifier (4 steps)

• Automatic Gain Control (AGC) for true line loss

compensation

• Microphone mute

• Key tone mode.

Supplies

• Provides a strong 3.35 V regulated supply for microcontroller or dialler

• Provides filtered power supply, optimized according to line current

• Filtered 2.0 V power supply output for electret microphone

• PD logic input for power-down.

• Duplex controller consisting of:

– signaland noise envelopemonitorsfor bothchannels

(with adjustable sensitivities and timing)

– decision logic (with adjustable switch-over and Idle

mode timing)

– voice switch control (with adjustable switching range

and constant sum of gain during switching).

APPLICATIONS

• Line powered telephone sets.

GENERAL DESCRIPTION

The TEA1098A is an analog bipolar circuit dedicated for telephonyapplications. It includesa line interface,handset (HS) microphone and earpiece amplifiers, handsfree (HF) microphone and loudspeaker amplifiers and a duplex controllerwith signal andnoisemonitors onbothchannels. Digital volume control is available both on earphone and loudspeaker amplifiers.

This IC provides a 3.35 V strong supply for a microcontroller and a 2.0 V filtered voltage supply for an electret microphone.

Handsfree

• Asymmetrical high input impedance for electret microphone

• Loudspeaker amplifier with single-ended rail-to-rail output and externally adjustable gain

• Dynamic limiter on loudspeaker amplifier to prevent distortion

• Digitalvolume controlon loudspeakeramplifier (8 steps)

ORDERING INFORMATION

TYPE NUMBER

NAME DESCRIPTION VERSION

TEA1098ATV VSO40 plastic very small outline package; 40 leads SOT158-1 TEA1098AH QFP44 plastic quad ﬂat package; 44 leads (lead length 1.3 mm);

body 10 × 10× 1.75 mm

2000 Mar 21 2

PACKAGE

SOT307-2

Philips Semiconductors Preliminary speciﬁcation

Speech and handsfree IC TEA1098A

QUICK REFERENCE DATA

= 15 mA; R

line

MUTE = HIGH; BPC = HIGH; measured according to test circuits; unless otherwise speciﬁed.

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

line

SLPE

BB(PD)

v(MIC-LN)

v(IR-RECO)

∆G

v(RECO-EARO)

v(TXI-TXO)

v(HFTX-LN)

v(HFRX-LSAO

SWR switching range − 40 − dB

∆SWR switching range adjustment with R

∆G

v(trx)

SLPE

=20Ω;Z

= 600 Ω; f = 1 kHz;T

line

=25°C; AGCpin connected to LN; PD = HIGH;HFC = LOW;

amb

line current operating range normal operation 11 − 130 mA

with reduced performance 1 − 11 mA

stabilized voltage between SLPE and GND

regulated supply voltage for internal circuitry

regulated supply voltage on pin V

current available on pin V

= 15 mA 3.4 3.7 4.0 V

line

= 70 mA 5.7 6.1 6.5 V

line

= 15 mA 2.75 3.0 3.25 V

line

= 70 mA 4.9 5.3 5.7 V

line

VBB> 3.35 V + 0.25 V (typ.) 3.1 3.35 3.6 V otherwise − V

− 0.25 − V

in speech mode − 11 − mA in handsfree mode − 9 − mA

current consumption on V

PD = LOW − 460 −µA

during power-down phase voltage gain from pin

= 5 mV (RMS) 43.3 44.3 45.3 dB

MIC

MIC+/MIC− to LN voltage gain from pin IR

(referenced to LN) to RECO gain voltage range between

VIR= 15 mV (RMS); HFC = HIGH

28.7 29.7 30.7 dB

−3 − +15 dB

pins RECO and EARO voltage gain from pin TXI to

TXO voltage gain from pin HFTX

= 3 mV (RMS);

TXI

= 30.1 kΩ

GATX

= 15 mV (RMS) 33.5 34.7 35.9 dB

HFTX

12.7 15.2 17.7 dB

to LN

) voltage gain from pin HFRX

to LSAO

= 30 mV (RMS);

HFRX

= 255 kΩ;

GALS

=70mA

line

SWR

referenced to

25.5 28 30.5 dB

−40 − +12 dB

365 kΩ

gain control range for

= 70 mA 5.45 6.45 7.45 dB

line

transmit and receive ampliﬁers affected by the AGC; with respect to I

=15mA

line

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Philips Semiconductors Preliminary speciﬁcation

Speech and handsfree IC TEA1098A

BLOCK DIAGRAM

REG

handbook, full pagewidth

LN 19 (15)

STARTER

LINE CURRENT DETECTION LOW VOLTAGE BEHAVIOUR

SLPE

20 (16)18(14)

SWITCH

SUPPLY

MANAGEMENT

(10) 14

(19) 23

(20) 24

MICS

AGC

GND

HFTX

DTMF

MIC+ MIC−

TXI

TSEN TENV

TNOI

RNOI RENV RSEN

GALS

LSAO

22 (18)

17 (13)

39 (36)

35 (32)

34 (31) 33 (30)

31 (28)

9 (4) 8 (3) 7 (2) 10 (5) 12 (7) 11 (6)

15 (11)

16 (12)

AGC

tail currents for preamps

ATTENUATOR

TX AND RX

ENVELOPE AND NOISE

DETECTORS

BUFFERS

AND

COMPARATORS

TEA1098A

DUCO LOGIC SWT STATUS

POWER-DOWN

CURRENT SOURCES

LOGIC

INPUTS

DECODING

VOICE

SWITCH

VOLUME

CONTROL

(38) 1

(37) 40

(39) 2 (40) 3

(27) 30 (26) 29

(29) 32

(24) 27 (25) 28

(21) 25

(22) 26

(41) 4 (42) 5

(1) 6

HFC

MUTE BPC

GATX TXO

GNDTX

SWT IDT

STAB

SWR

EVCI LVCI

HFRX

13 (8)

DLC

RECO GARX

EARO

38 (35) 37 (34)

36 (33)

DYNAMIC

LIMITER

Fig.1 Block diagram.

2000 Mar 21 4

ATTENUATOR

(17) 21

FCA140

Philips Semiconductors Preliminary speciﬁcation

Speech and handsfree IC TEA1098A

PINNING

SYMBOL

PD 1 38 power-down input (active LOW) MUTE 2 39 logic input (active LOW) BPC 3 40 logic input (active LOW) EVCI 4 41 logic input for digital volume control (earpiece and loudspeaker LSB) LVCI 5 42 logic input for digital volume control (loudspeaker MSB) n.c. − 43 not connected n.c. − 44 not connected HFRX 6 1 receive input for loudspeaker ampliﬁer TNOI 7 2 transmit noise envelope timing adjustment TENV 8 3 transmit signal envelope timing adjustment TSEN 9 4 transmit signal envelope sensitivity adjustment RNOI 10 5 receive noise envelope timing adjustment RSEN 11 6 receive signal envelope sensitivity adjustment RENV 12 7 receive signal envelope timing adjustment DLC 13 8 dynamic limiter capacitor for the loudspeaker ampliﬁer n.c. − 9 not connected V

GALS 15 11 loudspeaker ampliﬁer gain adjustment LSAO 16 12 loudspeaker ampliﬁer output GND 17 13 ground reference SLPE 18 14 line current sense LN 19 15 positive line terminal REG 20 16 line voltage regulator decoupling IR 21 17 receive ampliﬁer input AGC 22 18 automatic gain control/line loss compensation V

MICS 24 20 microphone supply STAB 25 21 reference current adjustment SWR 26 22 switching range adjustment n.c. − 23 not connected SWT 27 24 switch-over timing adjustment IDT 28 25 Idle mode timing adjustment TXO 29 26 handsfree microphone ampliﬁer output GATX 30 27 handsfree microphone ampliﬁer gain adjustment TXI 31 28 handsfree microphone ampliﬁer input GNDTX 32 29 ground reference for microphone ampliﬁers MIC− 33 30 negative handset microphone ampliﬁer input MIC+ 34 31 positive handset microphone ampliﬁer input

TEA1098ATV TEA1098AH

14 10 stabilized supply for internal circuitry

23 19 3.35 V regulated voltage supply for microcontrollers

DESCRIPTION

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Philips Semiconductors Preliminary speciﬁcation

Speech and handsfree IC TEA1098A

SYMBOL

DESCRIPTION

TEA1098ATV TEA1098AH

DTMF 35 32 dual tone multi-frequency input EARO 36 33 earpiece ampliﬁer output GARX 37 34 earpiece ampliﬁer gain adjustment RECO 38 35 receive ampliﬁer output HFTX 39 36 transmit input for line ampliﬁer HFC 40 37 logic input

handbook, halfpage

MUTE

BPC

EVCI

LVCI

HFRX

TNOI TENV TSEN

RNOI RSEN RENV

DLC V

GALS LSAO

GND

SLPE

REG

1 2 3 4 5 6 7 8 9

TEA1098ATV

11 12 13 14 15 16 17 18 19

FCA141

40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21

HFC HFTX RECO GARX EARO DTMF MIC+ MIC− GNDTX TXI GATX TXO IDT SWT SWR STAB MICS V

AGC IR

Fig.2 Pin configuration (TEA1098ATV).

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Speech and handsfree IC TEA1098A

handbook, full pagewidth

n.c.

LVCI

EVCI

BPC

MUTE

HFTX

RECO

n.c. 44

HFC

GARX

HFRX

TNOI

TENV

TSEN

RNOI

RSEN RENV

DLC

n.c.

GALS

15 LN

GND

SLPE

LSAO

Fig.3 Pin configuration (TEA1098AH).

FUNCTIONAL DESCRIPTION

All data given in this chapter are typical values, except when otherwise specified.

Supplies

TEA1098AH

REGIRAGC

This capacitor converted into an equivalent inductance realizes the set impedance conversion from its DC value (R

The IC regulates the line voltage at pin LN and can be calculated as follows:

EARO DTMF

32 31

MIC+

MIC− GNDTX

29 28

TXI GATX

TXO

IDT

25 24

SWT n.c.

MICS

STAB

) to its AC value (done by an external impedance).

SLPE

FCA142

SWR

LINE INTERFACE AND INTERNAL SUPPLY (PINS LN, SLPE, REG AND VBB)

The supply for the TEA1098A and its peripherals is obtained from the line. The IC generates a stabilized reference voltage (V

) between pins SLPE and GND.

ref

This reference voltage is equal to 3.7 V for line currents lower than 18 mA. It than increases linearly with the line current and reaches the value of 6.1 V for line currents higher than 45 mA. For line currents below 9 mA, the internal reference voltage generating V

is automatically

ref

adjusted to a lowervalue. This is the so-calledlow voltage area and the TEA1098A has limited performances in this area (see Section “Low voltage behaviour”). This reference voltage is temperature compensated.

The voltage between pins SLPE and REG is used by the internal regulator to generate the stabilized reference voltageand is decoupledby means ofacapacitor between pins LN and REG.

2000 Mar 21 7

SLPEIline

refRSLPE

I×+

SLPE

Ix–=

where: I

= line current

line

Ix= current consumed on pin LN (approximately a few µA) I

= current flowing through the R

SLPE

The preferred value for R

is 20 Ω. Changing this value

SLPE

resistor

will affect more than the DC characteristics; it also influences the transmit gains to the line, the gain control characteristic, thesidetone level and the maximum output swing on the line.

Philips Semiconductors Preliminary speciﬁcation

Speech and handsfree IC TEA1098A

handbook, full pagewidth

REG

GND

REG

4.7 µF

SLPE

TP1

TN1

from

preamp

SLPE

20 Ω

Fig.4 Line interface principle.

As can beseen fromFig.4, theinternal circuitryis supplied by pin VBB, which is a strong supply point combined with the line interface. The line current is flowing through the R

resistor and is sunk by the VBB voltage stabilizer,

SLPE

thusbecoming availablefor a loudspeakeramplifier orany peripheral IC. Its voltage is equal to 3.0 V for line currents lower than 18 mA. It than increases linearly with the line current and reaches the value of 5.3 V for line currents greater than 45 mA. It is temperature compensated.

TR2

GND

TR1

GND

Thereference voltageV

TN2

MGM298

canbe increasedbyconnecting

ref

an external resistor between pins REG and SLPE. For large line currents, this increase can slightly affect some dynamic performances such as maximum signal level on the line for 2% THD. The voltage on pin VBBis not affected by this external resistor; see Fig.5 for the main DC voltages.

The aim of the current switch TR1 and TR2 is to reduce distortionof largeAC line signals.Current I

SLPE

issupplied to VBBvia TR1 when the voltage on SLPE is greater than VBB+ 0.25 V.When thevoltageon SLPE islower than this value, the current I

is shunted to GND via TR2.

SLPE

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Speech and handsfree IC TEA1098A

handbook, full pagewidth

Voltages

(V)

0.00 0.01

0.02 0.05

0.040.03

Fig.5 Main DC voltages.

MGL439

SLPE

VBB

VDD

MICS

0.070.06

Line current (A)

SUPPLY FOR MICROCONTROLLER (PIN V

Thevoltage on theV

supplypoint follows thevoltage on VBBwitha difference typicallyequal to 250 mVand is internally

)

limited to 3.35 V. This voltage is temperature compensated. This supplypoint can provide a current up to 3 mAtypically. Its internal consumption stays low (a few 10 nA) as long as VDD does not exceed 1.5 V.

VDD can also be used as an input; in this case the voltage will be stabilised to 3.35 V up to 75 mA input current. VBB and VDDcan supply external circuits in the limit of currents provided from the line, taking into account the internal

current consumption.

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Philips Semiconductors Preliminary speciﬁcation

Speech and handsfree IC TEA1098A

100.0u

handbook, full pagewidth

(A)

10.0u

1.0u

100.0n

10.0n

1.0n

100.0p

10.0p

1.0

MGL438

1.5 2.5 3.0

2.0 VDD (V)

Fig.6 Current consumption on VDD.

SUPPLY FOR MICROPHONE (PINS MICS AND GNDTX) The MICS output can be used as a supply for an electret

microphone. Its voltage is equal to 2.0 V; it can source a current up to 1 mA and has an output impedance equal to 200 Ω.

LOW VOLTAGE BEHAVIOUR For line currents below 9 mA, the reference voltage is

automatically adjusted to a lower value; the VBB voltage follows the SLPE voltage with 250 mV difference. The excess current available for other purposes than DC biasing of the IC becomes small. In this low voltage area, the IC has limited performances.

When the VBBvoltage becomes lower than 2.7 V, the V

detector of the receive dynamic limiter on pin LSAO acts continuously, discharging the capacitor connected to pin DLC. In the DC condition, the loudspeaker is then automatically disabled below this voltage.

When VBBgoes below 2.5 V, the TEA1098A is forced into a low voltage mode whatever thelevels onthe logic inputs are. It is a speech mode with reduced performances only enablingthe microphone channel(between the MICinputs and LN) and the earpiece amplifier. These two channels are able to deliver signals for line currents as small as 3 mA. The HFC input is tied to GND sinking a current typically equal to 300 µA.

POWER-DOWN MODE (PIN PD) To reduce consumption during dialling or register recall

(flash),the TEA1098A isprovided withapower-down input (PD). When the voltage on pin PD is LOW, the current consumption from VBB and VDD is reduced to 460 µA typically. Therefore a capacitor of 470 µF on VBB is sufficient to power the TEA1098A during pulse dialling or flash. The PD input has a pull-up structure. In this mode, the capacitor C

is internally disconnected.

REG

2000 Mar 21 10

Philips Semiconductors Preliminary speciﬁcation

Speech and handsfree IC TEA1098A

Transmit channels (pins MIC+, MIC−, DTMF, HFTX and LN)

HANDSET MICROPHONE AMPLIFIER (PINS MIC+, MIC−

AND LN)

The TEA1098A has symmetrical microphone inputs. The input impedance between pinsMIC+ and MIC− is typically 70 kΩ. The voltage gainbetween pins MIC+/MIC− and LN is set to 44.3 dB. Without limitation from the output, the microphone input stage can accommodate signals up to 18 mV (RMS) at room temperature for 2% of Total Harmonic Distortion (THD). The microphone inputs are biased at one diode voltage.

Automatic gain control is provided for line loss compensation.

DTMF AMPLIFIER (PINS DTMF, LN AND RECO) The TEA1098A has an asymmetrical DTMF input. The

inputimpedance betweenpins DTMF andGND istypically 20 kΩ. The voltagegain betweenpins DTMF andLN isset to 25.35 dB. Without limitation from the output, the input stage can accommodate signals up to 180 mV (RMS) at room temperature for 2% of THD.

When the DTMF amplifier is enabled, dialling tones may be sent on the line. These tones can be heard in the earpiece or in the loudspeaker ata lowlevel. This is called theconfidence tone. Thevoltageattenuation between pins DTMF andRECO is typically−16.5 dB in handsfreemode (HFC HIGH), and −28.2 dB in handset mode (HFC LOW).

The DC biasing of this input is 0 V. The automatic gain control has no effect on these

channels.

HANDSFREE TRANSMIT AMPLIFIER (PINS HFTX AND LN)

The TEA1098A has an asymmetrical HFTX input, which is mainly intended for use in combination with the TXO output. The input impedance between pins HFTX and GND is typically 20 kΩ. The voltage gain between pins HFTX andLN is set to 34.7 dB. Without limitation fromthe output, the input stage can accommodate signals up to 95 mV (RMS) at room temperature for 2% of THD. The HFTX input is biased at two diodes voltage.

Automatic gain control is provided for line loss compensation.

Receive channels (pins IR, RECO, GARX, EARO and EVCI)

RX AMPLIFIER (PINS IR, RECO AND EVCI) The receive amplifier has one inputIR which is referred to

the line. The input impedance between pins IR and LN is typically 20 kΩ and the DC biasing between these pins is equal to one diode voltage.

When HFC = 0, the gain between pins IR (referred to LN) and RECO is typically 17.0 dB which compensates typically 15 dB lower than attenuation of the anti-sidetone network. The receive amplifier gain can be digitally increased with the 4-level logic input EVCI, providing 4 steps of 4.85 dB which apply in all handset receive modes. Without limitation from the output, the input stage can accommodate signals up to 50 mV (RMS) at room temperature for 2% of THD.

When HFC = 1, the gain is set automatically to 29.7 dB which compensate the anti-sidetone network attenuation minus 2.3 dB.

Thisreceive amplifier hasarail-to-rail outputRECO,which is designed for use with high ohmic (real) loads (larger than 5 kΩ). This output is biased at two diodes voltage.

Automatic gain control is provided for line loss compensation.

EARPIECE AMPLIFIER (PINS GARX AND EARO) The earpiece amplifier is an operational amplifier having

itsoutput (EARO)and its invertinginput (GARX)available. Its inputsignal comes, viaadecoupling capacitor,from the receive output RECO. It is used in combination with two resistors to get the required gain or attenuation compared to the receive gain. The typical resistor ratio is 4, which gives a 12 dB gain. The gain range can be chosen between 0 dB and 20 dB.

Two external capacitors C GAR and EARO) and C GAR and GND) ensure stability. The C

(connected between pins

GAR

(connected between pins

GARS

capacitor

GAR

provides a first-order low-pass filter. The cut-offfrequency corresponds to the time constant C relationship C

GARS

>=10×C

GAR

× RE2. The

GAR

must be fulfilled.

The earpiece amplifier has a rail-to-rail output EARO, biasedat two diodesvoltage.It is designedforuse with low ohmic (real) loads (150 Ω) or capacitive loads (100 nF in series with 100 Ω).

2000 Mar 21 11

Philips Semiconductors Preliminary speciﬁcation

Speech and handsfree IC TEA1098A

AGC (pin AGC)

The TEA1098A performs automatic line loss compensation,which fits wellwiththe trueline attenuation. The automatic gain control varies the gain of some transmit and receive amplifiers in accordance with the DC linecurrent. Thecontrolrange is6.45 dBfor G G

v(IR-RECO)

and 6.8 dB for G

v(HFTX-LN)

, which corresponds

v(MIC-LN)

and

approximately to a line length of 5.5 km for a 0.5 mm twisted-pair copper cable.

To enable this gain control, pin AGC must be shorted to pin LN. The start currentfor compensationcorresponds to a line current of typically 23 mA and the stop current to 57 mA. The start current can be increased by connecting an external resistor between pins AGC and LN. It can be increased up to 40 mA (using a resistor typically 80 kΩ). The start and stop current will be maintained in a ratio equal to 2.5. By leavingthe AGC pin open-circuit, thegain control is disabled and no line loss compensation is performed.

Handsfree application

As can be seen from Fig.4, a loop is formed via the sidetone network in the line interface part and the acoustic coupling between loudspeaker and microphone of the handsfree part. When this loop gain is greater than 1, howling occurs. In a full duplex application this would be the case. The loop-gain has to be much lower than 1 and therefore has to be decreased to avoid howling.

This is achieved by the duplex controller. The duplex controller of the TEA1098Adetects whichchannel has the ‘largest’ signal and then controls the gains of the microphone and loudspeaker amplifiersso thatthe sum of the gains remains constant.

As a result, in handsfree application, the circuit can be in three stable modes:

1. Transmit mode (TX mode). Thegain ofthemicrophone amplifier isat its maximum

and the gain of the loudspeaker amplifier is at its minimum.

2. Receive mode (RX mode). The gain of the loudspeaker amplifier is at its

maximum and the gain of the microphone amplifier is at its minimum.

3. Idle mode. The gain of the amplifiers is halfway between their

maximum and minimum value.

The difference between the maximum gain and minimum gain is called the switching range.

handbook, full pagewidth

telephone

line

sidetone

HYBRID

Fig.7 Handsfree telephone set principles.

2000 Mar 21 12

acoustic coupling

DUPLEX

CONTROL

MGM299

+ 28 hidden pages