Philips TEA1099H Datasheet

INTEGRATED CIRCUITS

DATA SH EET

TEA1099H

Speech and handsfree IC with
auxiliary inputs/outputs and analog
multiplexer

Product specification
Supersedes data of 1998 Jun 11
File under Integrated Circuits, IC03

1999 Apr 08

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

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

• Dual Tone Multi-Frequency (DTMF) input with
confidence tone on earphone and/or loudspeaker

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

• AGC: Automatic Gain Control for true line loss
compensation.

Supplies

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

• Provides filtered power supply, optimized according to
line current and compatible with external voltage or
current sources

• Filtered 2.0 V power supply output for electret
microphone

• Compatible with a ringer mode

• Power-Down (

Handsfree

• Asymmetrical high-impedance input for electret
microphone

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

• Dynamic limiter on loudspeaker amplifier to prevent
distortion

• Logarithmic volume control on loudspeaker amplifier via
linear potentiometer

• Duplex controller consisting of:
– Signal and noise envelope monitors for both

channels (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).

PD) logic input for power-down.

TEA1099H

Auxiliary interfaces

• General auxiliary output for transmit and receive
purposes

• Auxiliary transmit input with high signal level capability
dedicated to line transmission

• Auxiliary receive input with high signal level capability

• Integrated multiplexer for channels selection.

APPLICATIONS

• Line powered telephone sets

• Cordless telephones

• Fax machines

• Answering machines.

GENERAL DESCRIPTION

The TEA1099H is an analog bipolar circuit dedicated for
telephone applications. It includes a line interface, handset
(HS) microphone and earpiece amplifiers, handsfree (HF)
microphone and loudspeaker amplifiers, some specific
auxiliary Inputs/Outputs (I/Os) and an analog multiplexer
to enable the right transmit and/or receive channels.
The multiplexer is controlled by a logic circuit which
decodes four logic inputs provided by a microcontroller.
Thirteen different application modes have been defined
and can be accessed by selecting the right logic inputs.
An application mode is a special combination of transmit
and receive channels required by telephone applications.

This IC can be supplied by the line and/or by the mains if
available (in a cordless telephone or an answering
machine for example). It provides a 3.35 V supply for a
microcontroller or dialler and a 2.0 V filtered voltage supply
for an electret microphone. The IC is designed to facilitate
the use of the loudspeaker amplifier during ringing phase.

1999 Apr 08 2

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary

TEA1099H

inputs/outputs and analog multiplexer

QUICK REFERENCE DATA

I

= 15 mA; R

line

AUXC = LOW;

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

I

line

V

SLPE

V

BB

V

DD

V

ESI

I

ESI(ext)

I

BB

I

BB(pd)

G

v(MIC-LN)

G

v(IR-RECO)

∆G

v(QR)

G

v(TXIN-TXOUT)

G

v(HFTX-LN)

G

v(HFRX-LSAO)

SWRA switching range − 40 − dB

∆SWRA switching range adjustment with R

∆G

v(trx)

SLPE

=20Ω; Z

= 600 Ω; f = 1 kHz; T

line

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

amb

MUTT = HIGH; MUTR = HIGH; measured according to test circuits; unless otherwise specified.

line current operating range normal operation 11 − 140 mA

with reduced performance 1 − 11 mA

stabilized voltage between SLPE
and GND (V

ref

)

regulated supply voltage for
internal circuitry

regulated supply voltage on pin
V

DD

external voltage supply allowed

I

= 15 mA 3.4 3.7 4.0 V

line

I

= 70 mA 5.7 6.1 6.5 V

line

I

= 15 mA 2.75 3.0 3.25 V

line

I

= 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

BB

−− 6V

on pin ESI
external current supply allowed on

−− 140 mA

pin ESI
current available on pin V

BB

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

current consumption on V

BB

PD = LOW − 460 −µA

during power-down phase
voltage gain from pin

V

= 5 mV (RMS) 43.3 44.3 45.3 dB

MIC

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

VIR= 15 mV (RMS) 28.7 29.7 30.7 dB

(referenced to LN) to RECO
gain voltage range between pins

−3 − +15 dB

RECO and QR
voltage gain from pin TXIN to

TXOUT
voltage gain from pin HFTX to LN V
voltage gain from pin HFRX to

LSAO

V

= 3 mV (RMS);

TXIN

R

= 30.1 kΩ

GATX

= 15 mV (RMS) 33.5 34.7 35.9 dB

HFTX

V

= 20 mV (RMS);

HFRX

= 255 kΩ

R

GALS

referenced to

SWR

12.7 15.2 17.7 dB

25.5 28 30.5 dB

−40 − +12 dB

365 kΩ

gain control range for transmit and
receive amplifiers affected by the
AGC; with respect to I

=15mA

line

I

= 70 mA; on

line

G

v(MIC-LN)

G

v(IR-AUXO)

, G

v(IR-RECO)

5.45 6.45 7.45 dB

and

ORDERING INFORMATION

TYPE

NUMBER

NAME DESCRIPTION VERSION

PACKAGE

TEA1099H QFP44 plastic quad flat package; 44 leads (lead length 1.3 mm);

body 10 × 10 × 1.75 mm

1999 Apr 08 3

SOT307-2

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

BLOCK DIAGRAM

handbook, full pagewidth

LN

AGC

GND

HFTX 36

TXAUX 43

DTMF 32

15

18

13

ATT.

STARTER

LINE CURRENT DETECTION
LOW VOLTAGE BEHAVIOUR

AGC

Tail currents for preamps

REG SLPE
16 14

SWITCH

TEA1099H

SUPPLY

D6

MANAGEMENT

POWER-DOWN

CURRENT SOURCES

ANALOG

MULTIPLEXER

CONTROL

TEA1099H

V

10

BB

9

ESI
V

19

DD

20

MICS

38

PD

HFC37
MUTT39
MUTR40
AUXC41

MIC+ 31
MIC−

TXIN 28

TSEN 4
TENV 3

TNOI 2

RNOI 5
RENV 7
RSEN 6

GALS 11

LSAO 12

DLC 8

AUXO 44

RECO 35
GARX 34

QR 33

30

TX AND RX

ENVELOPE AND NOISE

DETECTORS

DYNAMIC

LIMITER

BUFFERS

AND

COMPARATORS

DUCO LOGIC
SWT STATUS

VOICE

SWITCH

VOLUME

CONTROL

ATT.

GATX27

TXOUT26
GNDTX29

SWT24
IDT25

STAB21

SWR22

VOL23

HFRX

1

IR17

RAUX42

Fig.1 Block diagram.

1999 Apr 08 4

MGM296

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

PINNING

SYMBOL PIN DESCRIPTION

HFRX 1 receive input for loudspeaker

amplifier or auxiliary receive
amplifier

TNOI 2 transmit noise envelope timing

adjustment

TENV 3 transmit signal envelope timing

adjustment

TSEN 4 transmit signal envelope sensitivity

adjustment

RNOI 5 receive noise envelope timing

adjustment

RSEN 6 receive signal envelope sensitivity

adjustment

RENV 7 receive signal envelope timing

adjustment

DLC 8 dynamic limiter capacitor for the

loudspeaker amplifier
ESI 9 external supply input
V

BB

GALS 11 loudspeaker amplifier gain

LSAO 12 loudspeaker amplifier output
GND 13 ground reference
SLPE 14 line current sense
LN 15 positive line terminal
REG 16 line voltage regulator decoupling
IR 17 receive amplifier input
AGC 18 automatic gain control/line loss

V

DD

10 stabilized supply for internal

circuitry

adjustment

compensation

19 3.35 V regulated voltage supply for

the microcontroller

TEA1099H

SYMBOL PIN DESCRIPTION

MICS 20 microphone supply output
STAB 21 reference current adjustment
SWR 22 switching range adjustment
VOL 23 loudspeaker volume adjustment
SWT 24 switch-over timing adjustment
IDT 25 Idle mode timing adjustment
TXOUT 26 HF microphone amplifier output
GATX 27 HF microphone amplifier gain

adjustment
TXIN 28 HF microphone amplifier input
GNDTX 29 ground reference for microphone

amplifiers
MIC− 30 negative HS microphone amplifier

input
MIC+ 31 positive HS microphone amplifier

input
DTMF 32 dual tone multi-frequency input
QR 33 earpiece amplifier output
GARX 34 earpiece amplifier gain adjustment
RECO 35 receive amplifier output
HFTX 36 transmit input for line amplifier or

auxiliary receive amplifier
HFC 37 logic input
PD 38 power-down input (active LOW)
MUTT 39 logic input (active LOW)
MUTR 40 logic input (active LOW)
AUXC 41 logic input
RAUX 42 auxiliary receive amplifier input
TXAUX 43 auxiliary transmit amplifier input
AUXO 44 auxiliary amplifier output

1999 Apr 08 5

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

handbook, full pagewidth

RAUX

TXAUX
43

42

AUXC

MUTR

41

40

TEA1099H

HFRX

TNOI
TENV
TSEN

RNOI
RSEN
RENV

DLC

ESI

V

BB

GALS

AUXO
44

1
2
3
4

5
6
7
8
9

10
11

MUTT
39

PD

38

HFC
37

HFTX

36

RECO
35

GARX
34

33
32
31
30
29
28
27
26
25
24
23

TEA1099H

QR
DTMF
MIC+
MIC−
GNDTX
TXIN
GATX
TXOUT
IDT
SWT
VOL

12

13

14

15

LN

GND

SLPE

LSAO

Fig.2 Pin configuration.

FUNCTIONAL DESCRIPTION

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

Supplies

L

INE INTERFACE AND INTERNAL SUPPLY (PINS LN, SLPE,

REG

AND V

BB

)

The supply for the TEA1099H 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 lower value. This is the so-called low voltage
area and the TEA1099H has limited performances in this
area (see Section “Low voltage behaviour”). This
reference voltage is temperature compensated.

21

16

REG

17

18

19

IR

AGC

DD

V

20

MICS

STAB

22

SWR

MGM297

The voltage between pins SLPE and REG is used by the
internal regulator to generate the stabilized reference
voltage and is decoupled by means of a capacitor between
pins LN and REG. This capacitor converted into an
equivalent inductance realizes the set impedance
conversion from its DC value (R

) to its AC value (done

SLPE

by an external impedance).
The IC regulates the line voltage at pin LN and it can be

calculated as follows:

V
I

V

=

LN

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

SLPE

resistor

1999 Apr 08 6

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

The preferred value for R
will affect more than the DC characteristics; it also
influences the transmit gains to the line, the gain control
characteristic, the sidetone level and the maximum output
swing on the line.

As can be seen from Fig.3, the internal circuitry is 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

becoming available for a loudspeaker amplifier or any
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.
See Fig.4 for the main DC voltages.

is 20 Ω. Changing this value

SLPE

TEA1099H

The aim of the current switch TR1 and TR2 is to reduce
distortion of large AC line signals. Current I
to VBB via TR1 when the voltage on SLPE is greater than
VBB+ 0.25 V. When the voltage on SLPE is lower than this
value, the current I

The reference voltage V

is shunted to GND via TR2.

SLPE

can be increased by connecting

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% Total Harmonic Distortion (THD).
The voltage on pin VBB is not affected by this external
resistor.

is supplied

SLPE

handbook, full pagewidth

LN

REG

GND

C

REG

4.7 µF

SLPE

R

SLPE

20 Ω

TP1

D1

R3

R2

TN1

R1

from

preamp

J1

Fig.3 Line interface principle.

TR2

GND

TR1

E1

TN2

J2

GND

E2

MGM298

D1

V

BB

1999 Apr 08 7

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

handbook, full pagewidth

8

voltages

(V)

6

4

2

0

0 0.01

0.02 0.05

TEA1099H

FCA049

LN

SLPE

V

BB

V

DD

MICS

0.040.03

I

line

(A)

0.070.06

Fig.4 Main DC voltages.

EXTERNAL SUPPLY (PINS ESI AND VBB)
The TEA1099H can be supplied by the line as well as by

external power sources (voltage or current sources) that
must be connected to pin ESI.

The IC will choose which supply to use according to the
voltage it can provide. A voltage supply on ESI is efficient
only if its value is greater than the working voltage of the
internal V

voltage stabilizer. Otherwise the IC continues

BB

to be line powered. The current consumed on this source
is at least equal to the internal consumption. It increases
with the voltage difference between the value forced on
ESI and the working voltage of the internal stabilizer.
The excess current compared to the internal consumption
becomes then available for other purposes such as
supplying a loudspeaker amplifier. The voltage source
should not exceed 6 V. If the value of the external voltage
source can be lower than the working voltage of the
internal stabilizer, an external diode is required to avoid
reverse current flowing into the external power supply.

In case of current source, the voltage on VBB and ESI
depends on the current available. It is internally limited to

6.6 V. The current source should not exceed 140 mA.

SUPPLY FOR MICROCONTROLLER (PIN V

V

DD

The voltage on V

supply point follows the voltage on V

DD

DD

)

BB

with a difference typically equal to 250 mV and is internally
limited to 3.35 V. This voltage is temperature
compensated. This supply point can provide a current up
to 3 mA typically. Its internal consumption stays low (a few
10 nA) as long as VDD does not exceed 1.5 V (see Fig.5).

An external voltage can be connected on VDD with limited
extra consumption on VDD (typically 100 µA). This voltage
source should not be lower than 3.5 V or higher than 6 V.

VBB and VDD can supply external circuits in the limit of
currents provided either from the line or from ESI, taking
into account the internal current consumption.

1999 Apr 08 8

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

8

10

handbook, full pagewidth

I

DD

(pA)

7

10

6

10

5

10

4

10

3

10

2

10

10

1.0

1.5 2.5 3.0

2.0

TEA1099H

FCA050

VDD (V)

Fig.5 Current consumption on VDD.

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

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

L

OW 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 VBB voltage reaches 2.7 V, the VBB detector of
the receive dynamic limiter on LSAO acts and discharges
the DLC capacitor. The loudspeaker is then automatically
disabled below this DC voltage.

When VBB becomes lower than 2.5 V, the TEA1099H is
forced into a low voltage mode whatever the levels on the
logic inputs are. It is a speech mode with reduced
performances only enabling the microphone channel
(between the MIC inputs 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.

OWER-DOWN MODE (PINS PD AND AUXC)

P
To reduce current consumption during dialling or register

recall (flash), the TEA1099H is provided with a
power-down input (PD). When the voltage on both pinsPD
and AUXC 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 TEA1099H
during pulse dialling or flash. The

PD input has a pull-up
structure, while AUXC has a pull-down structure. In this
mode, the capacitor C

R

INGER MODE (PINS ESI, V

is internally disconnected.

REG

, AUXC AND PD)

BB

The TEA1099H is designed to be activated during the
ringing phase. The loudspeaker amplifier can be used for
the ringing signal. The IC must be powered by an external
supply on ESI, while applying a HIGH level on the logic
input AUXC and a LOW level on

PD input. Only the HFRX
input and the LSAO output are activated, in order to limit
the current consumption. Some dynamic limitation is
provided to prevent the LSAO output from saturation and
VBB from being discharged below 2.7 V.

1999 Apr 08 9

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

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

ANDSET MICROPHONE AMPLIFIER (PINS MIC+, MIC− AND

H
LN)

The TEA1099H has symmetrical microphone inputs.
The input impedance between MIC+ and MIC− is
70 kΩ(typ.). The voltage gain between 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 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 TEA1099H has an asymmetrical DTMF input.
The input impedance between DTMF and GND is
20 kΩ (typ.). The voltage gain between pins DTMF and LN
is set 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 at a low level. This is called
the confidence tone. The voltage attenuation between pins
DTMF and RECO is typically equal to −16.5 dB.

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

channels.

UXILIARY TRANSMIT AMPLIFIER (PINS TXAUX AND LN)

A
The TEA1099H has an asymmetrical auxiliary input

TXAUX. The input impedance between TXAUX and GND
is 20 kΩ (typ.). The voltage gain between pins TXAUX and
LN is set to 12.5 dB. Without limitation from the output, the
input stage can accommodate signals up to 1.2 V (RMS)
at room temperature for 2% of THD. The TXAUX input is
biased at two diodes voltage.

Automatic gain control is provided for line loss
compensation.

TEA1099H

ANDSFREE TRANSMIT OUTPUT STAGE (PINS HFTX AND LN)

H
The TEA1099H has an asymmetrical HFTX input, which is

mainly intended for use in combination with the TXOUT
output. The input impedance between HFTX and GND is
20 kΩ (typ.). The voltage gain between pins HFTX and LN
is set to 34.7 dB. Without limitation from the 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.

M

ICROPHONE MONITORING ON TXOUT (PINS MIC+, MIC−

AND TXOUT)

The voltage gain between the microphone inputs
MIC+/MIC− and the output TXOUT is set to 49.8 dB. This
channel gives an image of the signal sent on the line while
speaking in the handset microphone. Using external
circuitry, this signal can be used for several purposes such
as sending dynamic limitation or anti-howling in a
listening-in application. The TXOUT output is biased at two
diodes voltage.

The automatic gain control has no effect on these
channels.

Receive channels (pins IR, RAUX, RECO, GARX and QR)

RX

AMPLIFIER (PINS IR AND RECO)

The receive amplifier has one input IR which is referred to
the line. The input impedance between pins IR and LN is
20 kΩ (typ.) and the DC biasing between these pins is
equal to one diode voltage. The gain between pins IR
(referred to LN) and RECO is typically equal to 29.7 dB.
Without limitation from the output, the input stage can
accommodate signals up to 50 mV (RMS) at room
temperature for 2% of THD.

This receive amplifier has a rail-to-rail output RECO, 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.

1999 Apr 08 10

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

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

its output (QR) and its inverting input (GARX) available.
Its input signal comes, via a decoupling capacitor, from the
receive RECO output. It is used in combination with two
resistors to get the required gain or attenuation compared
to the receive gain. It can be chosen between

−3 and +15 dB.
Two external capacitors C

and QR) and C

(connected between GARX and

GARS

GND) ensure stability. The C
1st-order low-pass filter. The cut-off frequency
corresponds to the time constant C
The relationship C

GARS

The earpiece amplifier has a rail-to-rail output QR, biased
at two diodes voltage. It is designed for use with low ohmic
(real) loads (150 Ω) or capacitive loads (100 nF in series
with 100 Ω).

A

UXILIARY RECEIVE AMPLIFIER (PINS RAUX AND RECO)

The auxiliary receive amplifier has an asymmetrical input
RAUX; it uses the RECO output. Its input impedance
between pins RAUX and GND is typically equal to 20 kΩ.
The voltage gain between pins RAUX and RECO is equal
to−2.4 dB. Without any limitation from the output, the input
stage can accommodate signals up to 0.95 V (RMS) at
room temperature for 2% of THD.

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

The automatic gain control has no effect on this channel.

Auxiliary amplifiers using AUXO (pins MIC+, MIC−,
HFTX, IR and AUXO)

The TEA1099H has an auxiliary output AUXO, biased at
two diodes voltage. This output stage is a rail-to-rail one,
designed for use with high ohmic (real) loads (larger than
5kΩ). The AUXO output amplifier is used in three different
channels, two transmit channels and one receive channel.

(connected between GARX

GAR

capacitor provides a

GAR

× Re2.

GAR

≥ 10 × C

must be fulfilled.

GAR

TEA1099H

A

UXILIARY AMPLIFIERS USING THE MICROPHONE INPUTS

(PINS MIC+, MIC− AND AUXO)
The auxiliary transmit amplifier using the microphone

MIC+ and MIC− inputs has a gain of 25.5 dB referenced to
AUXO. Without limitation from the output, the input stage
can accommodate signals up to 16 mV (RMS) at room
temperature for 2% of THD.

The automatic gain control has no effect on this channel.

UXILIARY AMPLIFIERS USING HFTX

A
(

PINS HFTX AND AUXO)

The auxiliary transmit amplifier using the HFTX input has
a gain of 15.2 dB referenced to AUXO.

The automatic gain control has no effect on this channel.

RX

AMPLIFIER USING IR (PINS IR AND AUXO)

The auxiliary receive amplifier uses pin IR as input.
The input is referred to LN and the DC biasing between
these two pins is one diode voltage. The voltage gain
between the input IR (referenced to LN) and the output
AUXO is typically equal to 32.8 dB, which compensates
typically the attenuation provided by the anti-sidetone
network.

Automatic gain control is provided for line loss
compensation.

AGC (pin AGC)

The TEA1099H performs automatic line loss
compensation, which fits well with the true line attenuation.
The automatic gain control varies the gain of some
transmit and receive amplifiers in accordance with the DC
line current. The control range is 6.45 dB for G
G

v(IR-RECO)

and G

v(IR-AUXO)

and 6.8 dB for the other

v(MIC-LN)

affected channels, which corresponds approximately to a
line length of 5.5 km for a 0.5 mm twisted-pair copper
cable.

To enable this gain control, the AGC pin must be shorted
to pin LN. The start current for compensation corresponds
to a line current equal to 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
equal to 80 kΩ). The start and stop current will be
maintained in a ratio equal to 2.5. By leaving the AGC pin
open-circuit, the gain control is disabled and no line loss
compensation is performed.

,

1999 Apr 08 11

Philips Semiconductors Product specification

Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer

Handsfree application

As can be seen from Fig.3, 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 TEA1099H detects which channel has the ‘largest’
signal and then controls the gain of the microphone
amplifier and the loudspeaker amplifier so that the sum of
the gains remains constant.

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

1. Transmit mode (TX mode).
The gain of the microphone amplifier is at 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.

TEA1099H

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

ANDSFREE MICROPHONE CHANNEL: PINS TXIN, GATX,

H
TXOUT

The TEA1099H has an asymmetrical handsfree
microphone input TXIN with an input resistance of 20 kΩ.
The DC biasing of the input is 0 V. The gain of the input
stage varies according to the mode of the TEA1099H.
In the transmit mode, the gain is at its maximum; in the
receive mode, it is at its minimum and in the Idle mode it is
halfway between maximum and minimum.

Switch-over from one mode to the other is smooth and
click-free. The output TXOUT is biased at two diodes
voltage and has a current capability equal to 20 µA (RMS).
In the transmit mode, the overall gain of the microphone
amplifier (from pins TXIN to TXOUT) can be adjusted from
0 up to 31 dB to suit specific application requirements.
The gain is proportional to the value of R

15.2 dB with R
output, the microphone input stage can accommodate
signals up to 18 mV (RMS) at room temperature for 2% of
THD.

AND GNDTX (see Fig.7)

= 30.1 kΩ. Without limitation from the

GATX

and equals

GATX

handbook, full pagewidth

telephone

line

sidetone

HYBRID

Fig.6 Handsfree telephone set principles.

1999 Apr 08 12

acoustic
coupling

DUPLEX

CONTROL

MGM299