Philips TEA1095T-C1, TEA1095-C1, TEA1095TS-C1 Datasheet

INTEGRATED CIRCUITS

DATA SHEET

TEA1095

Voice switched speakerphone IC

Product specification

1997 Nov 25

Supersedes data of 1996 Mar 22

File under Integrated Circuits, IC03

Philips Semiconductors	Product specification
Voice switched speakerphone IC	TEA1095

FEATURES

∙External power supply with power-down function

∙Transmit channel with:

–externally adjustable gain

–transmit mute function

∙Receive channel with:

–externally adjustable gain

–logarithmic volume control via a linear potentiometer

–receive mute function

∙Duplex controller consisting of:

–signal envelope and noise envelope monitors for both channels with:

externally adjustable sensitivity

externally adjustable signal envelope time constant externally adjustable noise envelope time constant

–decision logic with:

externally adjustable switch-over timing externally adjustable idle mode timing

externally adjustable dial tone detector in receive channel

–voice switch control with: adjustable switching range

constant sum of gain during switching

constant sum of gain at different volume settings.

ORDERING INFORMATION

APPLICATIONS

∙Mains, battery or line-powered telephone sets

∙Cordless telephones

∙Answering machines

∙Fax machines

∙Hands-free car kits.

GENERAL DESCRIPTION

The TEA1095 is a bipolar circuit, that in conjunction with a member of the TEA106X, TEA111X families of transmission or TEA1096 transmission/listening-in circuits offers a hands-free function. It incorporates a transmit amplifier, a receiver channel amplifier and a duplex controller with signal and noise monitors on both channels.

TYPE		PACKAGE
NUMBER	NAME	DESCRIPTION	VERSION
TEA1095	DIP24	plastic dual in-line package; 24 leads (600 mil)	SOT101-1
TEA1095T	SO24	plastic small outline package; 24 leads; body width 7.5 mm	SOT137-1
TEA1095TS	SSOP24	plastic shrink small outline package; 24 leads; body width 5.3 mm	SOT340-1

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Philips Semiconductors	Product specification
Voice switched speakerphone IC	TEA1095

QUICK REFERENCE DATA

VBB = 5 V; VGND = 0 V; f = 1 kHz; Tamb = 25 °C; MUTETX = LOW; MUTERX = LOW; PD = LOW; RVOL = 0 Ω; measured in test circuit of Fig.11; unless otherwise specified.

SYMBOL	PARAMETER	CONDITIONS	MIN.	TYP.	MAX.	UNIT
VBB	supply voltage		2.9	−	12.0	V
IBB	current consumption from pin VBB		−	2.7	3.8	mA
Gvtx	voltage gain from TXIN to TXOUT in	VTXIN = 1 mV (RMS);	−	15.5	−	dB
	transmit mode	RGATX = 30.1 kΩ
Gvtxr	voltage gain adjustment with RGATX		−15.5	−	+24.5	dB
Gvrx	voltage gain from RXIN to RXOUT in	VRXIN = 20 mV (RMS);	−	6.5	−	dB
	receive mode	RGARX = 16.5 kΩ
Gvrxr	voltage gain adjustment with RGARX		−20.5	−	+19.5	dB
SWRA	switching range		−	40	−	dB
SWRA	switching range adjustment	with RSWR referenced to	−40	−	+12	dB
		RSWR = 365 kΩ
Tamb	operating ambient temperature		−25	−	+75	°C

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Philips Semiconductors	Product specification
Voice switched speakerphone IC	TEA1095

BLOCK DIAGRAM

	7	VBB				TEA1095			GND	6
	13 PD
VBB	15	MUTETX			TRANSMIT CHANNEL				GATX	17	RGATX
CTXIN	18	TXIN							TXOUT	16
			V	I			I	V
											to transmission
RMIC									TXGND	14	circuit
RTSEN					DUPLEX CONTROLLER				IDT	12	RIDT
	24	TSEN	LOG
									Vref
CTSEN
											CSWT
			BUFFER						SWT	11
CTENV	23	TENV
						13
						mV
CTNOI			BUFFER		ATTEN-						RSTAB
	22	TNOI			UATOR				STAB	10
	19	RNOI
CRNOI			BUFFER			LOGIC	VOICE
							SWITCH
									SWR	9	RSWR
	20	RENV
					13 mV
CRENV			BUFFER
RRSEN	21	RSEN
			LOG		Vdt
CRSEN
RGARX	4	GARX				2
	5	RXOUT		V	I		I	V	RXIN	2
to loudspeaker											from transmission
amplifier											circuit
	1	MUTERX
				RECEIVE CHANNEL			VOLUME		VOL	8	RVOL
							CONTROL
									MBG350
					Fig.1	Block diagram.
1997 Nov 25						4

Philips Semiconductors	Product specification
Voice switched speakerphone IC	TEA1095

PINNING

SYMBOL	PIN	DESCRIPTION
MUTERX	1	receiver channel mute input
RXIN	2	receiver amplifier input
n.c.	3	not connected
GARX	4	receiver gain adjustment
RXOUT	5	receiver amplifier output
GND	6	ground reference
VBB	7	supply voltage input
VOL	8	receiver volume adjustment
SWR	9	switching range adjustment
STAB	10	reference current adjustment
SWT	11	switch-over timing adjustment
IDT	12	idle mode timing adjustment
PD	13	power-down input
TXGND	14	ground reference for the transmit
		channel
MUTETX	15	transmit channel mute input
TXOUT	16	transmit amplifier output
GATX	17	transmit gain adjustment
TXIN	18	transmit amplifier input
RNOI	19	receive noise envelope timing
		adjustment
RENV	20	receive signal envelope timing
		adjustment
RSEN	21	receive signal envelope sensitivity
		adjustment
TNOI	22	transmit noise envelope timing
		adjustment
TENV	23	transmit signal envelope timing
		adjustment
TSEN	24	transmit signal envelope sensitivity
		adjustment

handbook, halfpage
MUTERX	1		24	TSEN
RXIN	2		23	TENV
n.c.	3		22	TNOI
GARX	4		21	RSEN
RXOUT	5		20	RENV
GND	6	TEA1095	19	RNOI
VBB	7		18	TXIN
VOL	8		17	GATX
SWR	9		16	TXOUT
STAB	10		15	MUTETX
SWT	11		14	TXGND
IDT	12		13	PD
		MBG349

Fig.2 Pin configuration.

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Philips Semiconductors	Product specification
Voice switched speakerphone IC	TEA1095

FUNCTIONAL DESCRIPTION

The values given in the functional description are typical values except when otherwise specified.

A principle diagram of the TEA1096 is shown on the left side of Fig.3. The TEA1096 is a transmission and listening-in circuit. It incorporates a receiving amplifier for the earpiece, a transmit amplifier for the microphone, a loudspeaker amplifier and a hybrid. For more details on the TEA1096 circuit (please refer to Data Handbook IC03). The right side of Fig.3 shows a principle diagram of the TEA1095, a hands-free add-on circuit with a transmit amplifier, a receiver amplifier and a duplex controller.

As can be seen from Fig.3, a loop is formed via the sidetone network in the transmission circuit and the acoustic coupling between loudspeaker and microphone of the hands-free circuit. When this loop gain is greater than 1, howling is introduced. 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 TEA1095 detects which channel has the ‘largest’ signal and then controls the gains of the transmit amplifier and the receiver amplifier such that the sum of the gains remains constant. As a result, the circuit can be in three stable modes:

1.Transmit mode (Tx mode): the gain of the transmit amplifier is at its maximum and the gain of the receiver amplifier is at its minimum.

2.Receive mode (Rx mode): the gain of the receiver amplifier is at its maximum and the gain of the transmit 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.

	acoustic
	coupling
	telephone	HYBRID	DUPLEX
	line		CONTROL
	sidetone

TEA1096

TEA1095

MBG358

Fig.3 Hands-free telephone set principles.

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Philips Semiconductors	Product specification
Voice switched speakerphone IC	TEA1095

Supply: pins VBB, GND and PD

The TEA1095 must be supplied with an external stabilized voltage source between pins VBB and GND. In idle mode, without any signal, the internal supply current is 2.7 mA at VBB = 5 V.

To reduce current consumption during pulse dialling or register recall (flash), the TEA1095 is provided with a power-down (PD) input. When the voltage on PD is HIGH, the current consumption from VBB is 140 μA.

Transmit channel: pins TXIN, GATX, TXOUT, TXGND and MUTETX

The TEA1095 has an asymmetrical transmit input (TXIN) with an input resistance of 20 kΩ. The gain of the input stage varies according to the mode of the TEA1095. 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 capability at pin TXOUT is 20 μA (RMS).

In the transmit mode, the overall gain of the transmit amplifier (from pin TXIN to TXOUT) can be adjusted from 0 dB to 40 dB to suit application specific requirements.

The gain is proportional to the value of RGATX and equals 15.5 dB with RGATX = 30.1 kΩ.

A capacitor must be connected in parallel with RGATX to ensure stability of the transmit amplifier. Together with

RGATX, it also provides a first-order low-pass filter.

By applying a HIGH level on pin MUTETX, the transmit amplifier is muted and the TEA1095 is automatically forced into the receive mode.

	MUTETX				GATX	RGATX
VBB						CGATX
CTXIN	TXIN				TXOUT	to transmission
		V	I	I
					V	circuit
RMIC
	to	from		to	TXGND
	envelope	voice		logic
	detector	switch
						MBG357

Fig.4 Transmit channel.

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Philips Semiconductors	Product specification
Voice switched speakerphone IC	TEA1095
Receive channel

						to
	RGARX			to/from	envelope
		GARX		voice switch	detector
	CGARX
to loudspeaker		RXOUT	I	I	V
amplifier		V				RXIN	from transmission
							circuit
		MUTERX
				VOLUME		VOL	RVOL
				CONTROL
							MBG356

Fig.5 Receive channel.

RECEIVER AMPLIFIER: PINS RXIN, GARX, RXOUT AND

MUTERX

The TEA1095 has an asymmetrical input (RXIN) for the receiver amplifier with an input resistance of 20 kΩ. The gain of the input stage varies according to the mode of the TEA1095. In the receive mode, the gain is at its maximum; in the transmit 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.

In the receive mode, the overall gain of the receive amplifier can be adjusted from −14 dB to +26 dB to suit application specific requirements. The gain from RXIN to RXOUT is proportional to the value of RGARX and equals

6.5 dB with RGARX = 16.5 kΩ. A capacitor connected in parallel with RGARX can be used to provide a first-order low-pass filter.

By applying a HIGH level on pin MUTERX, the receiver amplifier is muted and the TEA1095 is automatically forced into the transmit mode.

VOLUME CONTROL: PIN VOL

The receiver amplifier gain can be adjusted with the potentiometer RVOL. A linear potentiometer can be used to obtain logarithmic control of the gain of the receiver amplifier. Each 950 Ω increase of RVOL results in a gain loss of 3 dB. The maximum gain reduction with the volume control is internally limited to the switching range.

Duplex controller

SIGNAL AND NOISE ENVELOPE DETECTORS: PINS TSEN, TENV, TNOI, RSEN, RENV AND RNOI

The signal envelopes are used to monitor the signal level strength in both channels. The noise envelopes are used to monitor background noise in both channels. The signal and noise envelopes provide inputs for the decision logic. The signal and noise envelopes detectors are shown in Fig.6.

For the transmit channel, the input signal at TXIN is 40 dB amplified to TSEN. For the receive channel, the input signal at RXIN is 0 dB amplified to RSEN. The signals from TSEN and RSEN are logarithmically compressed and buffered to TENV and RENV respectively. The sensitivity of the envelope detectors is set with RTSEN and RRSEN.

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Philips Semiconductors	Product specification
Voice switched speakerphone IC	TEA1095

The capacitors connected in series with the two resistors block any DC component and form a first order high-pass filter. In the basic application (see Fig.12), it is assumed

that VTXIN = 1 mV (RMS) and VRXIN = 100 mV (RMS) nominal and both RTSEN and RRSEN have a value of 10 kΩ. With the value of CTSEN and CRSEN at 100 nF, the cut-off frequency is at 160 Hz.

The buffer amplifiers leading the compressed signals to TENV and RENV have a maximum source current of 120 μA and a maximum sink current of 1 μA. Together with

the capacitors CTENV and CRENV, the timing of the signal envelope monitors can be set. In the basic application, the

value of both capacitors is 470 nF. Because of the logarithmic compression, each 6 dB signal increase means 18 mV increase of the voltage on the envelopes TENV or RENV at room temperature. Thus, timings can be expressed in dB/ms. At room temperature, the 120 μA sourced current corresponds to a maximum rise-slope of the signal envelope of 85 dB/ms. This is enough to track normal speech signals. The 1 μA current sunk by TENV or

RENV corresponds to a maximum fall-slope of 0.7 dB/ms. This is enough for a smooth envelope and also eliminates the effect of echoes on switching behaviour.

To determine the noise level, the signal on TENV and RENV are buffered to TNOI and RNOI. These buffers have a maximum source current of 1 μA and a maximum sink

current of 120 μA. Together with the capacitors CTNOI and CRNOI, the timing can be set. In the basic application of Fig.12, the value of both capacitors is 4.7 μF. At room

temperature, the 1 μA sourced current corresponds to a maximum rise-slope of the noise envelope of approximately 0.07 dB/ms. This is small enough to track background noise and not to be influenced by speech bursts. The 120 μA current that is sunk corresponds to a maximum fall-slope of approximately 8.5 dB/ms. However, during the decrease of the signal envelope, the noise envelope tracks the signal envelope so it will never fall faster than approximately 0.7 dB/ms. The behaviour of the signal envelope and noise envelope monitors is illustrated in Fig.7.

DUPLEX CONTROLLER

		to logic			to logic
LOG			LOG
from			from
transmit			receiver
amplifier			amplifier
TSEN	TENV	TNOI	RSEN	RENV	RNOI
RTSEN				RRSEN
CTSEN		CTENV	CTNOI	CRSEN	CRENV	CRNOI
						MBG355

Fig.6 Signal and noise envelope detectors.

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