30W BRIDGECAR RADIO AMPLIFIER
NO AUDIBLE POP DURING MUTE AND
STANDBYOPERATIONS
MUTINGTTL COMPATIBLE
VERYLOW STANDBY CONSUMPTION
PROGRAMMABLETURN ON DELAY
DIFFERENTIAL INPUT
SHORTCIRCUITPROTECTIONS:
RL SHORT - OUT TO GROUND - OUT TO V
OTHERPROTECTIONS:
- Load dump voltage surge
- LoudspeakerDC current
- Very inductive load
- Overratingtemperature
- Openground
DESCRIPTION
The TDA7256 is a class AB fullyprotected bridge
power amplifier, designed for car radio applica-
S
TDA7256
MULTIWATT11
ORDERING NUMBER: TDA7256
tions. The high current capability allows to drive
low impedance loads (up to 2Ω). The differential
inputs availability makes it particularlysuitable for
boostersand active loudspeakersapplications.
BLOCK DIAGRAM
October 1998
This is advanced information on a new product now in development or undergoing evaluation. Detailsare subject to change without notice.
1/10
TDA7256
PIN CONNECTION (Top view)
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Test Conditions Unit
Operating Supply Voltage 18 V
S
DC Supply Voltage 28 V
S
Peak Supply Voltage (for 50ms) 40 V
S
Output Peak Current (non repetiitive t = 0.1ms) internally limited
Output Peak Current Repetitive f > 10Hz 5.5 A
Power Dissipation (Tcase = 85°C) 36 W
Storage and Junction Temperature Range -40 to +150 °C
P
T
stg,TJ
V
V
V
I
o
I
o
tot
THERMAL DATA
Symbol Description Value Unit
R
th j-case
Thermal Resistance Junction-case Max 1.8 °C/W
2/10
TDA7256
ELECTRICAL CHARACTERISTICS
= 14.4V, RL=4Ω, f = 1KHz; T
(V
S
=25°C, unless otherwise
amb
specified)
Symbol Parameter Test Condition Min. Typ. Max. Unit
V
S
I
q
R
CMR Common Mode Rejection f = 1KHz, V
V
OS
P
o
d Distortion P
G
V
e
N
SVR Supply Voltage Rejection R
T
SD
Supply Voltage 8 18 V
Quiescent Drain Current 80 150 mA
Input Resistance 50 K
i
= 100mV 60 dB
in
Output Offset Voltage 150 mV
Output Power d = 10%
R
=4Ω
L
R
= 3.2Ω
L
R
=2
Ω
L
= 0.1W to 13W 0.05 0.5 %
o
18 22
26
30
Voltage Gain (CL) 36 dB
Total Input Noise Voltage Rg= 10KΩ, B = 22Hz to 22KHz 3 10 µV
= 10KΩ,Vr= 1Vrms,
g
45 60 dB
f = 300Hz
Muting Attenuation V
= 1Vrms,
ref
60 dB
f = 100Hz to 10KHz
Muting-in Threshold Voltage Pin 1 2.4 V
Muting-out Threshold Voltage Pin 1 0.8 V
Stand-by Attenuation Vref = 1Vrms 60 dB
Stand-by Current Consumption 100
Thermal Shut-down Junction
145 °C
Temperature
Ω
W
W
W
A
µ
Figure 1:
Testand Application Circuit
3/10
TDA7256
Figure 2:
P.C.and Layout of the fig.1(1:1 scale)
Figure 3:
4/10
Drain Current vs. SupplyVoltage
Figure4: Output Power vs. Supply Voltage
TDA7256
Figure 5: Output Power vs. Supply Voltage
Figure 7:
Distortionvs.OutputPower
Figure6:
Figure 8:
OutputPowervs. SupplyVoltage
Distortionvs. Output Power
Figure 9:
Distortionvs.OutputPower
Figure10: Distortionvs. Frequency
5/10
TDA7256
Figure 11: Distortionvs. Frequency
Figure 13:
CMRRvs. Frequency
Figure12: SVR vs. Frequency
Figure14: PowerDissipation& Efficiency vs.
OutputPower
Figure 15: Power Dissipation & Efficiency vs.
OutputPower
6/10
Figure 16: PowerDissipation& Efficiencyvs.
Output Power
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 maintaininglow 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
MUTE
The mute circuit (TTL compatible) acts at pream-
plifier level and disablesthe 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 lowerthan about 2 volt
Figure 18: Soft Muting
TURN-ON
The TDA7256 is fully poplessat turn-on thanks to
a delay circuit which keeps the output low during
the capacitorscharge transient.
The delay-timeis given by the following formula:
=800 C10 + 600 (C9 + C11) (
T
o
C9
C10
+ C11
+ 1)
TURN-OFF
The ground compatible structures and the choice
of a soft turn-off circuit ensure a fully popless operation.
OUTPUTSTAGE
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
R
=4 ohm , 30W with RL=2 ohm).
L
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.
SHORTCIRCUITPROTECTION
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,allowingalso loudspeakerprotection.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
(fewµA). 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-bypins.
7/10
TDA7256
Figure 19:
SilentTransientsThroughtheMute and Stand-by pins.
8/10
TDA7256
DIM.
Dia1 3.65 3.85 0.144 0.152
MIN. TYP. MAX. MIN. TYP. MAX.
A5
B 2.65 0.104
C 1.6 0.063
D 1 0.039
E 0.49 0.55 0.019 0.022
F 0.88 0.95 0.035 0.037
G 1.45 1.7 1.95 0.057 0.067 0.077
G1 16.75 17 17.25 0.659 0.669 0.679
H1 19.6 0.772
H2 20.2 0.795
L 21.9 22.2 22.5 0.862 0.874 0.886
L1 21.7 22.1 22.5 0.854 0.87 0.886
L2 17.4 18.1 0.685
L3 17.25 17.5 17.75 0.679 0.689 0.699
L4 10.3 10.7 10.9 0.406 0.421 0.429
L7 2.65 2.9 0.104 0.114
M 4.25 4.55 4.85 0.167 0.179 0.191
M1 4.73 5.08 5.43 0.186 0.200 0.214
S 1.9 2.6 0.075 0.102
S1 1.9 2.6 0.075 0.102
mm inch
0.197
0.713
OUTLINE AND
MECHANICAL DATA
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.
1995SGS-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 - UnitedKingdom - U.S.A.
10/10
Loading...