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TEA7532
MONITOR AMPLIFIER
.PROGRAMMABLEGAI .ON/ .LOWVOLTAGE .POWER:100mWAT5V
OFF POSITION
N IN STEPS OF 6 dB
DESCRIPTION This 16 pins IC is designed for monitor (loudspeaker) telephone set and provides : a) Signal amplification for monitoring (loudspeaker) b) Antiacoustic feedback (antilarsen) c) Antidistortion by automatic gain adaptation d) Antilarsen adjustment (full duplex) BLOCK DIAGRAM
DIP16
SO16
ORDERING NUMBERS : TEA7532DP (DIP16) TEA7532FP (SO16)
July 1993
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TEA7532
PIN CONNECTION (Top view)
PIN DESCRIPTION
N 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Symbol ADJ ALADJ ADS VLS MIC1 MIC2 FAL TC1 INP LS1 VREF LS2 GND PG0 PG1 ON/OFF Description Adjust Internal Reference V LS Antilarsen Adjustement Antidistortion Supply Microphone Input Microphone input Antilarsen Filter Antilarsen Time Constant Input Signal Output Loudspeaker 1 Internal Resistance Output Loudspeaker 2 Ground Inputs Program Level to Loudspeaker
ABSOLUTE MAXIMUM RATINGS
Symbol Top VLS ILS VL Parameter Temperature Range Supply Voltage Supply Current for T > 300ms for T 300ms Voltage Level (pins, PG0, PG1, on/off) Value -5 to + 45 6 90 150 0.6 > to VS + 0.6 Unit C V mA mA V
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ELECTRICAL CHARACTERISTICS (Tamb = 25oC, ILS = 30mA unless otherwise specified)
Symbol VLS1 VLSM VADJ G G000 G001 G010 G011 G100 THD Parameter VLS Supply VLS Maximum Voltage Pin 1 V10 - V12 Loudspeaker Amplifier Gain = V9 Test Conditions ILS = 2mA (fig. 7) ILS = 30mA (fig. 7) Ipin 1 = 50A (fig. 7 ; So = closed) ILS = 2mA to 30mA (fig. 7) ON/OFF PG0 PG1 12 18 24 30 14 20 26 32 - 30 16 22 28 34 - 20 2 dB dB dB dB dB % Min. 2.6 Typ. Max. 3.0 3.4 3.15 3.4 5.5 1.25 1.4 Unit V V V V
1.1
Distortion
G2 ZMICIN ZINPIN ZIN2 VOFFS ION/OFF IPG0 IPG1 ION/OFF IPG0 IPG1 VIL ON/OFF VIL PG0 VIL PG1 VIH ON/OFF VIH PG0 VIH PG1 GMIC Vg GATT
[V(10) - V(12)]/V2 Microphone Input Earphone Input Antilarsen Adjustment Input Ouput Offset [V(10) - V(12)] Input Current ON State
GND GND GND GND VLS GND GND VLS GND VLS VLS GND X X VLS f = 300Hz to 2kHz, V10 - V12 = 0.8VRMS, G = G011, (fig. 8) PG0 = PG1 = VLS, V8 = 0.8V (fig. 8) Symetrical at (pins 5-6) Asymetrical at (pin 6) fig. 9 (fig. 9) G011 ; (fig. 8) VPG1 = 0V ; (fig. 8) VPG1 = VLS ; (fig. 8)
30
32 4.5 2.8 1.2
34
dB k k k mV A A A A A A V V V V V V dB V dB dB
2.2 1 - 50 - 10 - 10 - 10
3.4 1.45 50
-5 -5 -5 1 1 1 0.45 0.45 0.45
Input Current OFF State
Input Voltage ON State
Input Voltage OFF State
Microphone Gain = V(7)/[V(5) - V(6)] Voltage Pin 8 Loudspeaker Attenuated Gain = [V(10) - V(12)]/V(9)
VMIC = 10mVRMS, f = 2kHz (fig. 10) G011 ; V8 = 0.6V ; (fig. 10) G011 ; V8 = 0.4V ; (fig. 10)
1.5 1.5 1.5 22.5 0.48 20
23.5 0.67 - 30 30
24.5 0.75 - 20
FUNCTIONAL DESCRIPTION TEA7532 performs the following functions : The circuit amplifies the incoming signal and feeds it to the loudspeaker. PG0 and PG1 inputs are used to set the loudspeaker gain in a range of 32dB to 14dB in 6dB steps. The TEA7532 inputs (PG0, PG1, ON/OFF) permit the loudspeaker to be cut-off thus ensuring privacy of communication.
- The antilarsen (antiacoustic feedback) system is incorporated. - The maximum power available on a 50 impedance loudspeaker is 25mW at 3 volts and 100mW at 5V. Limit values for external components : R3 min = 5 k (R3 adjust VLS), R7 max = 390 k, R6 min = R7/35 R max betweenpin 5 and 6 = 10k + C min = 10nF.
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Figure 1 : LoudspeakerGain Versus Voltage on Pin (3) - (8) with Pin 2 Open. Figure 2 :LoudspeakerGain Versus Voltage on Pin (3) - (8) and Versus R2. (*)
(*) ATTENUATION = Zin2 (1.2 K) + R2 (E X T)
Zin2 (1.2 K)
R2 = 10 K ATT = 20 dB R2 = 3 K ATT 10 dB
Figure 3 : AC Output Voltage Versus Amplifier Gain.
Figure 4 : Power Available on Loudspeaker Versus VLS Typical Curve.
Figure 5 : Distortion Versus Output Power.
Figure 6 : Output Power Versus Supply Current.
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TEA7532
TEST CIRCUITS Figure 7 : ShuntvoltageRegulator/ Reference Voltage at Pin 1. Figure 8 : Loudspeaker Amplifier : Gain/Distor tion/Output Offset.
S1 1 0 0 0 S2 X 0 1 0 S3 X 0 0 1
G1XX G000 G010 G001
*G=
V (10) - V (12) = V (9)
Vout V (9)
* VOFFS with Vin = 0. Note : S0 open for VLS 1 S0 close for VLSM. VLS = 1 G ND = 0
Figure 9 : Impedance ZMIC, ZINP and Zin2.
Figure 10 : Antiacoustic Feedback System at G011.
Zmic =
1.1 V I6
; Zinp =
1.1 V I9
; Zin2 =
1.1 V I2
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CIRCUIT DESCRIPTION TEA7532 is a 16 pin DIL integrated circuit providing the following facilities : - Loudspeaker amplifier 1.1. LOUDSPEAKER AMPLIFIER Figure 11.
-
Antiacoustic feed-back system (antilarsen system)
The amplifier is divided into 3 main sections. - Automatic Gain Control (AGC) - Preamplifier - Push-pull amplifier (bridge structure) a) The AGC section is used for the antilarsen and antidistortion system. * When used in a telephoneset to avoid larsen effect the AGC automatically decreases loudspeaker amplifier gain. * When the required output level exceeds the capabilities of the available current, the AGC Figure 12.
decreases the loudspeaker amplifier gain to avoid distortion. b) The preamplifier permits step control of amplifier gain in steps of 6 dB, using pins PG0 and PG1, which may be controlled using switches or by a microprocessor. The amplifier may be muted using the ON/OFF control signal (pin 16). c) The output amplifier uses a double push-pull configuration(H bridge) to get maximum dynamic range under limited supply conditions.
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TEA7532
Amplifier dc supply. In transmission mode, the supply voltage is controlled by the internal shunt DC regulator. For this reason, the TEA7532 should be supplied from a current source Figure 13. (see : supply considerations). An antidistortion system is embodied which provides AGC control to avoid loudspeaker distortion under current-limited conditions.
Circuit action. When the supply voltage is insufficient, the voltage at pin 1, falls below the reference voltage 1.1 V, resulting in transistor (TR) beingswitched off, resulting in zero current flow in resistor R. This state enables the gain control system. Under these conditions, the shunt DC supply will switch at a rate determined by the time constant of the RC network on pin 3. This switching action accomodates normal speech Figure 14 .
characteristics under low supply conditions. 1.2. ANTIACOUSTIC FEED-BACK SYSTEM (ANTILARSEN SYSTEM) The purpose of this system is to control AGC action in order to avoid acoustic feed-back between the loudspeaker and the microphone, when used in a telephone set.
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Principle of operation. When examining the spectral density of the voice area and the larsen area, it can be seen that the Figure 15. dominant features of each exist in different frequency bands.
To extract the larsen component, the microphone signal is first filtered by a second order filter (formed Figure 16.
by two first order filters), then amplified and rectified in order to produce the AGC control signal.
Zin : 4 k A=
V7
V5 - V6
= 15
The first filter is generated by the capacitors on pins 5 and 6 ; the second filter by the R-C network on pin 7.
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TEA7532
Figure 17 : Antilarsen System Filter Response.
Filter on pins 5 & 6
f2 = C9 + C10 2 Zin C9 C10
Filter on pin 7
f1 = 1 2 (R5 + R6) C5 1 2 R5 C5
f3 =
Antilarsen system Filter response
If f2 = f3 the Antilarsen system filter is equivalent to a second order filter. C9 + C10 1 = 2 Zin C9 C10 2 R5 C5
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TEA7532
A complete telephone set has two antilarsen systems : circuit (for - one in the transmission network ; example : TEA7051) antisidetone Figure 18. one in the loudspeaker amplifier (for example : TEA7532). Together these form a high efficiency antilarsen system.
-
PIN FUNCTIONS PIN 1 : ADJUST VLS This pin is used to adjust the IC supply voltage. PIN 2 : ANTILARSEN ADJUSTMENT The AC signal at this pin is amplified to the loudspeaker without AGC attenuation. PIN 3 : AUTOMATIC GAIN CONTROL FILTER The antidistortion system response is adjusted by the R-C network on this pin. The AGC will be switched ON when the level on pin 3 is greaterthan thereference voltage (0.4V), the RCnetwork charges (current source ON) or discharges (current source OFF) according to the supply voltage.
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TEA7532
THEORETICAL VOLTAGE ON PIN 3 Figure 19 :
Figure 20.
The value of R affects the system time constant and the charge/discharge duty cycle. The value of C only affects the system time constant. R should be greater or equalthan 150k for correct AGC operation.
PIN 4 : CIRCUIT SUPPLY VOLTAGE With pin 1 open circuit, VLS is internally stabilized at 2.8 V.
Whenthe TEA7532is underAGC control, the voltage on this pin varies slightly (due to AGC action).
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TEA7532
PIN 5/6 : MICROPHONE INPUTS These are used for antilarsen control. PIN 7 : ANTILARSEN FILTER 1 The second filter of the antilarsen system (1 st filter : pins 5-6) is formed by the RC network R5C5. In order to obtain a second order filter for the antilarsen system, the cut-off frequency defined at this pin, should be the same as that chosen for the first filter. For correct TEA7532 operation R6 and R5 should be fixed at 10 k and 1 k respectively. PIN 8 : ANTILARSEN FILTER 2 The gain and the response of the antilarsen system can be adjusted respectively by the resistor and the capacitor on this pin, according to the acoustic characteristics of the telephone set. The value of the resistor should not exceed 390 k. When the voltage on this pin exceeds the threshold voltage of 0.4 V, the AGC system is enabled. Figure 21. - "H" Mode This is for low voltage working, but at a higher supply current. The highest output power is available in this mode, due to the 5.5 V maximum supply voltage restriction, imposed by the TEA7532. Loudspeakerimpedancerecommendedvalue : 50. Maximum gain available between earphone input and loudspeaker output : 32 dB. PIN 9 : EARPHONE INPUT Input for loudspeaker signal. PIN 10-12 : LOUDSPEAKER OUTPUTS Maximum output voltage : Vpp = 2 VLS - 2.5 V (with a gain of 32 dB). Maximum output current : depending of the supply current. Two loudspeakerconnection methods are possible, using the amplifier in either "H" mode or "B" mode. Note : It is advisable to connect a 47 nF capacitor in parallel with the loudspeaker (between pins 10 and 12).
Figure 22.
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TEA7532
- "B" Mode This allows higher voltage operation, but at a lower supply current. Loudspeakerimpedancerecommendedvalue : 25 . Maximum gain available between earphone input and loudspeaker output : 32 - 6 = 26 dB. Figure 23. PIN 11 : Vref : INTERNAL REFERENCE Output which provides an internally regulated reference voltage. Vref = 1.1 V typical MAXIMUM AVAILABLE CURRENT : 5 A
PIN 13 : GROUND PIN 14-15 : GAIN ADJUSTMENT INPUTS These pins are used to adjust the loudspeaker amplifier gain. Four steps of 6 dB/step are available (pin open circuit = high level). PIN 16 : LOUDSPEAKER MUTING. This pin is used to mute the loudspeaker. Pin opencircuit : high level = loudspeaker muted. Pin low level : louspeaker enabled (see connection of pins 14 and 15).
PG0 1 1 0 0
PG1 1 0 1 0 Gmax Gmax - <0> 6 dB Gmax - 12 dB Gmax - 18 dB
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DIP16 PACKAGE MECHANICAL DATA
DIM. Min. a1 B b b1 D E e e3 F i L Z 3.3 1.27 8.5 2.54 17.78 7.1 5.1 0.130 0.050 0.51 0.77 0.5 0.25 20 0.335 0.100 0.700 0.280 0.201 1.65 mm Typ. Max. Min. 0.020 0.030 0.020 0.010 0.787
DIP16.TBL PM-DIP16.EPS
inch Typ. Max.
0.065
a1
I
b Z
B e3
e
L
b1
E
D
16
9
1
8
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F
TEA7532
SO16 PACKAGE MECHANICAL DATA
Dimensions Min. A a1 a2 b b1 C c1 D E e e3 F G L M S 3.8 4.6 0.5 9.8 5.8 1.27 8.89 4.0 5.3 1.27 0.62 8 (max.)
o
Millimeters Typ. Max. 1.75 0.1 0.2 1.6 0.35 0.19 0.5 45 (typ.) 10 6.2 0.386 0.228
o
Inches Min. Typ. Max. 0.069 0.004 0.008 0.063 0.014 0.007 0.020 0.018 0.010
0.46 0.25
0.394 0.244
SO16.TBL
0.050 0.350 0.150 0.181 0.020 0.157 0.209 0.050 0.024
L C
G c1
a2
A
s E
e3
D M
PM-SO16.EPS
16
9
1
8
F
a1
b
e
b1
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Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of SGS-THOMSON Microelectronics. (c) 1994 SGS-THOMSON Microelectronics - All Rights Reserved SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco - The Netherlands Singapore - Spain - Sweden - Switzerland - Taiwan - Thaliand - United Kingdom - U.S.A.
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