TEA7532 MONITOR AMPLIFIER .. .. PROGRAMMABLE GAIN IN STEPS OF 6 dB ON/OFF POSITION LOW VOLTAGE POWER : 100 mW AT 5 V 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) DIP16 SO16 ORDERING NUMBERS : TEA7532DP (DIP16) TEA7532FP (SO16) BLOCK DIAGRAM July 1993 1/16 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 2/16 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 TEA7532 ELECTRICAL CHARACTERISTICS (Tamb = 25oC, ILS = 30mA unless otherwise specified) Symbol VLS1 VLSM VADJ G G000 G001 G010 G011 G100 THD 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 Parameter VLS Supply VLS Maximum Voltage Pin 1 V10 − V12 Loudspeaker Amplifier Gain = V9 Distortion [V(10) – V(12)]/V2 Microphone Input Test Conditions ILS = 2mA (fig. 7) ILS = 30mA (fig. 7) Ipin 1 = 50µA (fig. 7 ; So = closed) ILS = 2mA to 30mA (fig. 7) ON/OFF PG0 VPG1 = 0V ; (fig. 8) Input Current OFF State VPG1 = VLS ; (fig. 8) 1.1 Typ. Max. 3.0 3.4 3.15 3.4 5.5 1.25 1.4 G011 ; (fig. 8) 12 18 24 30 14 20 26 32 – 30 16 22 28 34 – 20 2 dB dB dB dB dB % 30 32 4.5 34 dB kΩ 2.2 1 – 50 2.8 1.2 3.4 1.45 50 kΩ kΩ mV – 10 – 10 – 10 –5 –5 –5 1 1 1 0.45 0.45 0.45 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) 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. Unit V V V V PG1 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) Earphone Input Antilarsen Adjustment Input Ouput Offset [V(10) – V(12)] Input Current ON State Min. 2.6 1.5 1.5 1.5 22.5 0.48 20 23.5 0.67 – 30 30 24.5 0.75 – 20 µA µA µA µA µA µA V V V V V V dB V dB dB - The antilarsen (antiacoustic feedback) system is incorporated. - The maximum power available on a 50Ω impedance loudspeaker is 25mW at 3 volts and 100mW at 5V. Limit values for external components : R3 min = 5 kΩ (R3 adjust VLS), R7 max = 390 kΩ, R6 min = R7/35 R max betweenpin 5 and 6 = 10kΩ + C min = 10nF. 3/16 TEA7532 Figure 1 : LoudspeakerGain Versus Voltage on Pin (3) - (8) with Pin 2 Open. (*) ATTENUATION = Zin2 (1.2 K) Zin2 (1.2 K) + R2 (E X T) Figure 2 :LoudspeakerGain Versus Voltage on Pin (3) - (8) and Versus R2. (*) 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. 4/16 TEA7532 TEST CIRCUITS Figure 8 : Loudspeaker Amplifier : Gain/Distor tion/Output Offset. Figure 7 : ShuntvoltageRegulator/ Reference Voltage at Pin 1. G1XX G000 G010 G001 •G= V (10) – V (12) = V (9) S1 1 0 0 0 S2 X 0 1 0 S3 X 0 0 1 Vout V (9) • VOFFS with Vin = 0. Note : S0 open for VLS 1 S0 close for VLSM. V LS = 1 G ND = 0 Figure 9 : Impedance ZMIC, ZINP and Zin2. Zmic = 1.1 V I6 ; Zinp = 1.1 V I9 ; Zin2 = Figure 10 : Antiacoustic Feedback System at G011. 1.1 V I2 5/16 TEA7532 CIRCUIT DESCRIPTION TEA7532 is a 16 pin DIL integrated circuit providing the following facilities : - Loudspeaker amplifier - Antiacoustic feed-back system (antilarsen system) 1.1. LOUDSPEAKER AMPLIFIER Figure 11. 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. 6/16 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. 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 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. Figure 14 . 7/16 TEA7532 Principle of operation. When examining the spectral density of the voice area and the larsen area, it can be seen that the dominant features of each exist in different frequency bands. Figure 15. To extract the larsen component, the microphone signal is first filtered by a second order filter (formed by two first order filters), then amplified and rectified in order to produce the AGC control signal. Figure 16. Zin : 4 kΩ 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. 8/16 TEA7532 Figure 17 : Antilarsen System Filter Response. Filter on pins 5 & 6 f2 = C9 + C10 2π Zin C9 C10 Filter on pin 7 f1 = f3 = 1 2π (R5 + R6) C5 1 2π R5 C5 Antilarsen system Filter response If f2 = f3 the Antilarsen system filter is equivalent to a second order filter. C9 + C10 1 = 2π Zin C9 C10 2π R5 C5 9/16 TEA7532 A complete telephone set has two antilarsen systems : in the transmission circuit (for example : - one TEA7051) antisidetone network ; one in the loudspeaker amplifier (for example : TEA7532). Together these form a high efficiency antilarsen system. - Figure 18. 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. 10/16 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. TEA7532 THEORETICAL VOLTAGE ON PIN 3 Figure 19 : - 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 150kΩ for correct AGC operation. Figure 20. 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). 11/16 TEA7532 PIN 5/6 : MICROPHONE INPUTS PIN 9 : EARPHONE INPUT These are used for antilarsen control. Input for loudspeaker signal. PIN 7 : ANTILARSEN FILTER 1 PIN 10-12 : LOUDSPEAKER OUTPUTS 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. 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). For correct TEA7532 operation R6 and R5 should be fixed at 10 kΩ and 1 kΩ 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 kΩ. When the voltage on this pin exceeds the threshold voltage of 0.4 V, the AGC system is enabled. Figure 21. Figure 22. 12/16 - ”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 : 50Ω. Maximum gain available between earphone input and loudspeaker output : 32 dB. TEA7532 - ”B” Mode This allows higher voltage operation, but at a lower supply current. Loudspeakerimpedancerecommendedvalue : 25 Ω. Maximum gain available between earphone input and loudspeaker output : 32 - 6 = 26 dB. PIN 11 : Vref : INTERNAL REFERENCE Output which provides an internally regulated reference voltage. Vref = 1.1 V typical MAXIMUM AVAILABLE CURRENT : 5 µA Figure 23. PIN 13 : GROUND PG0 PG1 PIN 14-15 : GAIN ADJUSTMENT INPUTS 1 1 Gmax These pins are used to adjust the loudspeaker amplifier gain. Four steps of 6 dB/step are available (pin open circuit = high level). 1 0 Gmax - <0> 6 dB 0 1 Gmax - 12 dB 0 0 Gmax - 18 dB 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). 13/16 TEA7532 DIP16 PACKAGE MECHANICAL DATA mm DIM. Min. 0.51 B 0.77 Max. Min. Typ. Max. 0.020 1.65 0.030 0.065 b 0.5 0.020 b1 0.25 0.010 D 20 0.787 E 8.5 0.335 e 2.54 0.100 e3 17.78 0.700 F 7.1 0.280 i 5.1 0.201 L 3.3 0.130 0.050 I 1.27 b1 L a1 Z b B DIP16.TBL a1 Typ. inch e E Z e3 9 1 8 F 16 14/16 PM-DIP16.EPS D TEA7532 SO16 PACKAGE MECHANICAL DATA Millimeters Dimensions Min. Inches Typ. Max. A Typ. Max. 1.75 0.1 0.069 0.2 a2 0.004 0.008 1.6 0.063 b 0.35 0.46 0.014 0.018 b1 0.19 0.25 0.007 0.010 C 0.5 0.020 o c1 45 (typ.) D 9.8 10 0.386 0.394 E 5.8 6.2 0.228 0.244 e 1.27 e3 0.050 8.89 SO16.TBL a1 Min. 0.350 F 3.8 4.0 0.150 0.157 G 4.6 5.3 0.181 0.209 L 0.5 1.27 0.020 0.050 M 0.62 0.024 o 8 (max.) G c1 e a1 b A a2 C L s e3 b1 S E D 9 1 8 F 16 PM-SO16.EPS M 15/16 TEA7532 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. 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. 16/16