TDA7256 30W BRIDGE CAR RADIO AMPLIFIER NO AUDIBLE POP DURING MUTE AND STANDBY OPERATIONS MUTING TTL COMPATIBLE VERY LOW STANDBY CONSUMPTION PROGRAMMABLE TURN ON DELAY DIFFERENTIAL INPUT SHORT CIRCUIT PROTECTIONS: RL SHORT - OUT TO GROUND - OUT TO VS OTHER PROTECTIONS: - Load dump voltage surge - Loudspeaker DC current - Very inductive load - Overrating temperature - Open ground DESCRIPTION The TDA7256 is a class AB fully protected bridge power amplifier, designed for car radio applica- MULTIWATT11 ORDERING NUMBER: TDA7256 tions. The high current capability allows to drive low impedance loads (up to 2Ω). The differential inputs availability makes it particularly suitable for boosters and active loudspeakers applications. BLOCK DIAGRAM October 1998 1/10 This is advanced information on a new product now in development or undergoing evaluation. Details are subject to change without notice. TDA7256 PIN CONNECTION (Top view) ABSOLUTE MAXIMUM RATINGS Symbol Test Conditions Unit VS Operating Supply Voltage 18 V VS DC Supply Voltage 28 V VS Peak Supply Voltage (for 50ms) 40 V Io Output Peak Current (non repetiitive t = 0.1ms) Io Output Peak Current Repetitive f > 10Hz Ptot Tstg, TJ Parameter internally limited 5.5 Power Dissipation (Tcase = 85°C) Storage and Junction Temperature Range A 36 W -40 to +150 °C THERMAL DATA Symbol Rth j-case 2/10 Description Thermal Resistance Junction-case Max Value Unit 1.8 °C/W TDA7256 ELECTRICAL CHARACTERISTICS (VS = 14.4V, RL = 4Ω, f = 1KHz; Tamb = 25°C, unless otherwise specified) Symbol Parameter VS Supply Voltage Iq Quiescent Drain Current Ri Input Resistance CMR Common Mode Rejection VOS Output Offset Voltage Po Output Power d Distortion Test Condition Min. Typ. 8 80 f = 1KHz, Vin = 100mV mA KΩ 60 18 Po = 0.1W to 13W dB eN Total Input Noise Voltage R g = 10KΩ, B = 22Hz to 22KHz SVR Supply Voltage Rejection R g = 10KΩ, Vr = 1Vrms, f = 300Hz 45 Muting Attenuation Vref = 1Vrms, f = 100Hz to 10KHz 60 Muting-in Threshold Voltage Pin 1 2.4 Muting-out Threshold Voltage Pin 1 Stand-by Attenuation Vref = 1Vrms 0.5 36 3 mV W W W 22 26 30 0.05 Voltage Gain (CL) % dB 10 60 µV dB dB V 0.8 V 100 µA 60 dB Stand-by Current Consumption Thermal Shut-down Junction Temperature V 150 150 d = 10% R L = 4Ω R L = 3.2Ω R L = 2Ω Unit 18 50 GV TSD Max. 145 °C Figure 1: Test and Application Circuit 3/10 TDA7256 Figure 2: P.C. and Layout of the fig.1 (1:1 scale) Figure 3: Drain Current vs. Supply Voltage 4/10 Figure 4: Output Power vs. Supply Voltage TDA7256 Figure 5: Output Power vs. Supply Voltage Figure 6: Output Power vs. Supply Voltage Figure 7: Distortion vs. Output Power Figure 8: Distortion vs. Output Power Figure 9: Distortion vs. Output Power Figure 10: Distortion vs. Frequency 5/10 TDA7256 Figure 11: Distortion vs. Frequency Figure 12: SVR vs. Frequency Figure 13: CMRR vs. Frequency Figure 14: Power Dissipation & Efficiency vs. Output Power Figure 15: Power Dissipation & Efficiency vs. Output Power Figure 16: Power Dissipation & Efficiency vs. Output Power 6/10 TDA7256 CIRCUIT DESCRIPTION INPUT STAGE The input stage is a differential type preamplifier stage with two independent inputs and two outputs in phase opposition. It is designed for particular linearity characteristics in order to have output amplitude large enough (1VPP) yet maintaining low distortion. The voltage gain of the stage is 6 dB.The possibility to use the differential input allows the system immunity to common-mode noise in case of long wire connections (fig. 17 ) Figure 17: Balanced -Unbalanced Input TURN-ON The TDA7256 is fully popless at turn-on thanks to a delay circuit which keeps the output low during the capacitors charge transient. The delay-time is given by the following formula: To = 800 C10 + 600 (C9 + C11) ( C10 + 1) C9 + C11 TURN-OFF The ground compatible structures and the choice of a soft turn-off circuit ensure a fully popless operation. OUTPUT STAGE It is a power stage designed in a way of being able to drive loads up to 2 ohm in bridge configuration without bootstrap capacitors (22 W with RL=4 ohm , 30W with RL=2 ohm). MUTE The mute circuit (TTL compatible) acts at preamplifier level and disables the inputs without changing the DC voltage values. In such a way the operation is fully popless.The use of a RC network produces a soft reduction of the audio signal providing the best effect from the acoustic point of view (fig 18). The mute circuit is also activated during turnon/turn-off operations when the voltage at standby pin is lower than about 2 volt Figure 18: Soft Muting SVR The noises coming from the car environment are essentially inside the bandwith from 300 Hz to 6 KHz. The ripple rejection circuit which utilizes also the gain capacitors C11,C9 ensures in this frequency range a rejection typ. of 60dB. SHORT CIRCUIT PROTECTION The short circuit protection circuits intervene in the following cases: - s.c. between one output and ground - s.c. between one output and +Vs - s.c. between the outputs In the first two cases they stop the current in both the final stages,allowing also loudspeaker protection.In the last case the current is limited, thus avoiding the load point to reach the SOA of the output transistors. STAND-BY In stand-by condition the current generators are disabled:the current drops to a very low value (few µA). Also this function is fully popless. Fig. 19 shows the silent transients of turn-on and turn-off operations through both the mute and the stand-by pins. 7/10 TDA7256 Figure 19: Silent Transients Through the Mute and Stand-by pins. 8/10 TDA7256 DIM. mm MIN. TYP. A B inch MAX. MIN. TYP. 5 2.65 C D 0.197 0.104 1.6 OUTLINE AND MECHANICAL DATA 0.063 1 0.039 E 0.49 0.55 0.019 F 0.88 0.95 0.035 G G1 1.45 16.75 1.95 17.25 0.057 0.659 H1 H2 19.6 1.7 17 MAX. 0.022 0.037 0.067 0.669 0.077 0.679 0.772 20.2 0.795 L 21.9 22.2 22.5 0.862 0.874 0.886 L1 L2 21.7 17.4 22.1 22.5 18.1 0.854 0.685 0.87 0.886 0.713 L3 17.25 17.5 17.75 0.679 0.689 0.699 L4 L7 10.3 2.65 10.7 10.9 2.9 0.406 0.104 0.421 0.429 0.114 M 4.25 4.55 4.85 0.167 0.179 0.191 M1 S 4.73 1.9 5.08 5.43 2.6 0.186 0.075 0.200 0.214 0.102 S1 1.9 2.6 0.075 0.102 Dia1 3.65 3.85 0.144 0.152 Multiwatt11 V 9/10 TDA7256 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. 1995 SGS-THOMSON Microelectronics - All Rights Reserved MULTIWATT is a Registered Trademark of SGS-THOMSON Microelectronics 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. 10/10