TEA7092 Fast Delivery |IC PHOENIX CO.,LIMITED

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TEA7092
TELEPHONE ANALOG FRONT END
TEA7092
TELEPHONE ANALOG FRONT END
July 1996
SPEECH. DC LINE CURRENT RANGE FROM 6 TO 120mA. EXTERNALLY ADJUSTABLE : Tx AND Rx GAIN MAXIMUM TRANSMIT LEVEL RETURN LOSS SIDETONE NETWORKS Tx AND Rx AGC (LINE CURRENT START UP
VALUE AND SLOPE). SOFTCLIPPING ON Tx CHANNEL. SQUELCH ON Tx CHANNEL TO REDUCE NOISE
ENVIRONMENT AND TO IMPROVE HOWLING
IMMUNITY IN LOUDHEARING MODE. RECEIVING AMPLIFIER FOR PIEZO AND
ELECTRODYNAMIC TRANSDUCERS. FREQUENCY GENERATOR FOR WAITING
MELODY. ERROR BEEP GENERATOR. HOLD LINE CURRENT DETECTOR FOR
TRANSFER/AUTO RELEASE FEATURE. PROGRAMMABLE BY MICROCONTROLLER
SERIAL BUS : -6dB ON Tx CHANNEL +6dB ON Rx CHANNEL AGC INHIBITION ON Tx AND Rx CHANNELS
FOR PABX USE SQUELCH INHIBITION
GROUP LISTENING / ON HOOK DIALING. ANTI-HOWLING WITH ACOUSTIC FEED-
BACK SYSTEM COUPLED TO SQUELCH. RING MELODY CONTROL AND ERROR
BEEP GENERATORS. PROGRAMMABLE BY MICROCONTROLLER
SERIAL BUS : DIGITAL VOLUME CONTROL (7 STEPS OF
4dB EACH) AND OFF MODE
HANDFREE INTERFACE. PINS AND SOFTWARE FACILITY FOR EASY
INTERCONNECTION WITH HANDSFREE
CONTROLLER I.C. LIKE TEA7540
RING ON LOUDSPEAKER. EMBEDDED SWITCH MODE POWER SUP-
PLY DRIVER TO FEED THE LOUDSPEAKER
AMPLIFIER DURING RING MODE
.PROGRAMMABLE BY MICROCONTROLLER
SERIAL BUS : DIGITAL VOLUME CONTROL (15 STEPS OF
4dB EACH) AND OFF MODE RING FREQUENCY GENERATOR (MORE
THAN 200 FREQUENCIES AVAILABLE)
DIALING .PROGRAMMABLE BY MICROCONTROLLER
SERIAL BUS : DTMF GENERATOR 2V DC LINE VOLTAGE DURING THE MAKE
PERIOD IN PULSE MODE
MICROCONTROLLER INTERFACE.3.5V STABILIZED SUPPLY .TWO WIRES SERIAL BUS INTERFACE.RING INDICATOR .PON LINE CURRENT INDICATOR.RESET SIGNAL .LINE CURRENT VARIATION INDICATOR
(FOR TRANSFER FEATURE) .OSCILLATOR WITH STAND BY MODE
CORDLESS AND ANSWERING MACHINE
INTERFACE.SELF BIASED LOUDSPEAKER AMPLIFIER
AND MICROCONTROLLER INTERFACE FOR
ANSWERING MACHINE.SIGNAL INPUT AND OUTPUT INTERFACE
FOR CORDLESS .VRMC SUPPLY CAN BE EXTERNALLY FORCED
TO 5V FOR EASY INTERFACE WITH A MAIN
POWERED MICROCONTROLLER
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DESCRIPTION
The TEA7092 is a Telephone set Analog Front End
(TAFE) interface intended for use in conjunction
with a microcontroller.
In this configuration the TEA7092 provides a world-
wide telephone set with loudhearing and melody
ringer on loudspeaker. An handsfree telephone set
can be built by adding the TEA7540 handsfree
controller.
The simple interface with a +5V main supply allows
to use the TEA7092 in terminal like Answering
machine, FAX and cordless base station.
Repertory dialer (memory on MCU) and various
features (HOLD, Tone/Pulse, Flash, Mute, adjust-
able Ringer and Loudspeaker levels...) are pro-
grammable by the MCU through the serial bus
interface.
The MCU through the serial bus interface.
The concept using TAFE and Microcontroller is
called BICHIP approach.
BENEFITS
The benefits of this concept are : Saving of external components. Easy upgrade of the features (memories, LCD
driver, Answering machine, FAX, Cordless ...).R eplacement o f configuration switches
(PABX/Public, Tone/Pulse) and potentiometers
for loudspeaker and ringer control, by EEPROM
settings. Reliability and cost improvements.
PIN CONNECTIONS
TEA7092
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PIN DESCRIPTION
TEA7092
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BLOCK DIAGRAM
TEA7092
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ABSOLUTE MAXIMUM RATINGS
Note: Typical Thermal resistance TQFP44 Copper lead frame 70° K/W @ 1W.
0246 8 10 12 140
(mA)
VL (V)
Figure 1 : Safe Area
TEA7092
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DC CHARACTERISTICS (Tamb = 25°C, see Test 1)
Between IL = 8mA and IL = 20mA the DC slope is fixed by RS and RSLP :
VL(IL) = RS x (40E-6 + 0.5E-3 x IL) + RSLP/55 x (IL - 5.6E-3).
For line current higher than 20mA the slope is fixed by RSLP : VL(IL) = VL (20E-3) + RSLP/55 x (IL - 20E-3).
RETURN LOSS (Tamb = 25°C, see Test 2
TRANSMIT CHARACTERISTICS
The maximum gain Gtl is adjustable between 44
and 56dB versus RGT value
Gtl = 20 x log 
820 x ( RZ // RL + R3 ) // ZIN
RGT // 50kΩ
ZIN = internal impedance at Pin VL # 8kΩ.
The AGC variation is programmable through two
external resistors connected on Pins ILL and ISL.
ILL is the line current at which the gain is at the
maximum value and ISL is the line current at which
the gain is at the maximum value minus 6dB. For
line current lower than ILL or higher than ISL, the
transmit and receive gains have a constant value.
The following formulas give RLL and RSL values
versus ILL and ISL.
RSL = 310
ISL − 5.6mA and RLL = 310
ILL − 5.6mA
Tx Softclipping (see Figure 2)
0.2 0.5 1 2 5 10 20 100
(V
RMS
VMIC1-MIC2 (mVRMS)
D(V
) (%)
Figure 2 : Tx Softclipping and Distortion
at IL = 20mA
TEA7092
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Maximum Level on Line in Tx (see Figure 3)
The minimum operating voltage of the TEA7092 is 2.5V . At low line current value, when the voltage over
the TEA7092 is low, the softclipping function automatically limits the AC dynamic to avoid to reach the 2.5V
limit on the TEA7092.
When the DC voltage over the TEA7092 is high enough, the AC dynamic is limited at a value fixed by the
external resistor RSOFT connected on Pin SOFTL.
The Value of RSOFT is performed by : RSOFT = (RS x 50E-6 - 0.8 - VacPeak) / 40E-6
Tx Characteristics (Tamb = 25°C, f = 1kHz, see Test 3)
Squelch on Transmit Channel (Tamb = 25°C, f = 1kHz, IL = 20mA, see Test3)
The principle of the squelch is to reduce the transmit gain as soon as the amplitude of the signal on the
microphone is lower than a fixed threshold voltage, VT2.
TRANSMIT CHARACTERISTICS (continued)
(V)
IL (mA) 40 60 80 1000
Figure 3 : Line Peak Voltage versus DC Line
Current
Gtlmax
Gtlmax - Gsq
VT1 VT2 Vem2
Transmit
Gain (dB)
Vem
(dBV)
Vem1
Microphone AC Voltage
Figure 4 : Transmit Gain versus Microphone
AC Input Signal
TEA7092
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RECEIVE CHARACTERISTICS (Tamb = 25°C, f = 1kHz)
The sidetone of the TEA7092 uses two networks, these two networks are internally mixed between long line
length and short line length.
The following equation gives the sidetone impedance versus line current : ZAL = K x ZALL + (1 - K) x ZASL
K = 1 for IL = ILL ; K = 0 for IL = ISL, and K varies linearly between 1 and 0 when IL varies between ILL and ISL.
It is possible to use only the standard one sidetone concept by short-circuited Pins SNSL ans SNLL.
Gain Control Inhibition Facility For PABX Application
(Tamb = 25°C, IL = 20mA, f = 1kHz / No AGC mode selected 0010100)
LOUDSPEAKER AMPLIFIER PART
Loudspeaker Amplifier Channel (Tamb = 25°C, f = 1kHz, RLS = 50Ω, Vem = 0)
The Loudspeaker amplifier channel has a maximum gain of 35dB between Pin LSIN and Pin LSOUT . This
gain is programmable through the serial bus interface, 7 steps of 4dB each.
To avoid distortion, the output level on the loudspeaker is controlled by a softclipping function, the time
constant of this feature is connected to LSSOF pin.
TEA7092
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LOUDSPEAKER AMPLIFIER PART (continued)
Antiacoustic Feedback (Tamb = 25°C, IL = 20mA, see Test 4)
The antiacoustic feedback system is coupled to the microphone squelch. As soon as the level on the handset
microphone is higher than VT2, the transmit gain increases and the loudspeaker gain decreases. So the transmit
and loudspeaker gains are never simultaneously at maximum gain, which reduces larsen effect.
Figure 5 : Loudspeaker Gain GLS versus Voltage on Microphone
RING MODE
Loudspeaker Power Supply in Ring Mode (Tamb = 25°C, RLS = 50Ω, see Test 5)
In ring mode, it is neccessary to convert the high voltage / low current power input to a low voltage / high
current power, output to be able to drive a 50Ω loudspeaker, the external switch mode power supply driven
by the TEA7092 realizes this feature.
The switch mode power supply, through external component values, fixes the impedance and the start up
threshold level.
The volume control in ring mode is the same than the one used in loudspeaking mode for the highest steps,
8 steps of 4dB, and 5 more steps of 4dB each have been added, by using the code 0111011, for the lowest
one, by this way the maximum depth in ring mode for the volume control is 48dB.
Ring Frequency
The frequencies of the ring are given by : Fring = Fi.
Fi can take one of the following values : 19455Hz, 21308Hz, 23551Hz or 26321Hz, and n varies between
1 and 63. Fi and n correspond to 2 codes sent on the serial bus.
TEA7092
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DTMF GENERATOR (Tamb = 25°C, see Test 3)
Unwanted frequencies comply with CEPT 46-03.
SINE WAVE GENERATOR ( Tamb = 25°C, IL = 20 & 90mA, see Test 3)
The sine wave generator uses the same path than the DTMF generator. Sinus wave frequencies are the
half of the DTMF frequencies.
ERROR BEEP GENERATOR
The frequencies of the error beep generator are given by : FEB = Fi.
Fi can take one the following values : 19455Hz, 21308Hz, 23551Hz or 26321Hz, and n varies between 1
and 63.
Error beep generator code generates square wave signal in the earphone.
Error beep generator code following by group listening code generate square wave signal in the earphone
and in the loudspeaker.
TEA7092
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MICROCONTROLLER INTERFACE
Microcontroller Power Supply
The microcontroller power supply consists in a
serial regulator which generates a 3.5V regulated
supply on VRMC Pin, from an unregulated voltage
applied on VMC or VLS Pin.
The VMC Pin can be supplied either by the line, a
battery or any DC generator. The use of VMC input
allows to regulate the output VRMC voltage for an
LCD display. With no load, the quiescent current,
is 60μA. For an output current of 1.8mA, the typical
drop voltage between VMC and VRMC Pins is
150mV.
Microcontroller Control Signals
RESET : This output is setting to “1” when VRMC
reaches the 2.6V threshold level. This output goes
back to "0" : If VRMC goes below 2.5V or If the Reset code (0010111) is sent on the serial
bus interface and if PON output is at level "0".
When the Reset code has been previously sent,
Pin RESET goes back to an high level, if VRMC is
higher than the rise threshold, only on a rise edge
of PON signal. If this PON rise edge does not
appear, the RESET Pin remains at low logic level
even if VRMC goes upper 2.6V.
When PON output is at level "1", the Reset code is
inhibited.
PON : This output goes high when VRMC reaches
the 2.6V threshold level and the line current value
is upper than 12mA. As soon as the Reset output
is at level "1", the 4mA line current threshold detec-
tor can be sent through the serial bus interface
(0111001) to check if the line current value is be-
tween 4 and 12mA.
RI/VI : In Ring mode : This output goes to level "1" if : Pin RSU > 19V Pin VRMC > 2.6V In Off-Hook mode : This output manages the line
current variation indicator for transfer function
and this information is used by the microcontroller
to manage the transfer from one telephone set to
an other one connected in parallel on the same
line.
Figure 6 : Microprocessor Power Supply Block Diagram
TEA7092
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Reset and Power On
MICROCONTROLLER INTERFACE (continued)
Figure 7 : Telephone Set Powered from the Line, IL > IREF1, without Batteries
TEA7092
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Partno	Mfg	Dc	Qty	Available	Descript
TEA7092	ST	N/a	7	avai	TELEPHONE ANALOG FRONT END