TDA7294SV ST Microelectronics, TDA7294SV Datasheet - Page 8

• Manufacturer Part Number: TDA7294SV
• Description: 100V - 100W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY
• Manufacturer: ST Microelectronics

TDA7294S
The TDA7294S is a monolithic MOS power ampli-
fier which can be operated at 90V supply voltage
(100V with no signal applied) while delivering out-
put currents up to 6.5 A.
This allows the use of this device as a very high
power amplifier (up to 100W as peak power with
T.H.D.=10 % and Rl = 4 Ohm); the only drawback
is the power dissipation, hardly manageable in
the above power range.
The typical junction-to-case thermal resistance of
the TDA7294S is 1
To avoid that, in worst case conditions, the chip
temperature exceedes 150
tance of the heatsink must be 0.038
max ambient temperature of 50
As the above value is pratically unreachable; a
high efficiency system is needed in those cases
where the continuous RMS output power is higher
than 50-60 W.
The TDA7294S was designed to work also in
higher efficiency way.
For this reason there are four power supply pins:
two intended for the signal part and two for the
power part.
T1 and T2 are two power transistors that only
operate when the output power reaches a certain
threshold (e.g. 20 W). If the output power in-
creases, these transistors are switched on during
the portion of the signal where more output volt-
age swing is needed, thus ”bootstrapping” the
power supply pins (#13 and #15).
The current generators formed by T4, T7, zener
diodes Z1, Z2 and resistors R7,R8 define the
minimum drop across the power MOS transistors
of the TDA7294S. L1, L2, L3 and the snubbers
C9, R1 and C10, R2 stabilize the loops formed by
the ”bootstrap” circuits and the output stage of the
TDA7294S.
By considering again a maximum average
output power (music signal) of 20W, in case
of the high efficiency application, the thermal
resistance value needed from the heatsink is
2.2
All components (TDA7294S and power tran-
sistors T1 and T2) can be placed on a
1.5
electrically insulated from the heatsink.
Since the total power dissipation is less than that
of a usual class AB amplifier, additional cost sav-
ings can be obtained while optimizing the power
supply, even with a high heatsink .
BRIDGE APPLICATION
Another application suggestion is the BRIDGE
configuration, where two TDA7294S are used.
In this application, the value of the load must not
be lower than 8Ohm for dissipation and current
capability reasons.
A suitable field of application includes HI-FI/TV
subwoofers realizations.
8/13
o
o
C/W (Vs = 45V and Rl= 8Ohm).
C/W heatsink, with the power darlingtons
o
C/W (max= 1.5
o
C, the thermal resis-
o
C).
o
C/W).
o
C/W (@
The main advantages offered by this solution are:
- High power performances with limited supply
- Considerably high output power even with high
With Rl= 8 Ohm, Vs = 25V the maximum output
power obtainable is 150 W, while with Rl=16
Ohm, Vs =
(Music Power).
APPLICATION NOTE: (ref. fig. 7)
Modular Application (more Devices in Parallel)
The use of the modular application lets very high
power be delivered to very low impedance loads.
The modular application implies one device to act
as a master and the others as slaves.
The slave power stages are driven by the master
device and work in parallel all together, while the
input and the gain stages of the slave device are
disabled, the figure below shows the connections
required to configure two devices to work to-
gether.
THE BOOTSTRAP CAPACITOR
For compatibility purpose with the previous de-
vices of the family, the boostrap capacitor can be
connected both between the bootstrap pin (6) and
the output pin (14) or between the boostrap pin
(6) and the bootstrap loader pin (12).
When the bootcap is connected between pin 6
and 14, the maximum supply voltage in presence
of output signal is limited to 80V, due the boot-
strap capacitor overvoltage.
When the bootcap is connected between pins 6
and 12 the maximum supply voltage extend to the
full voltage that the technology can stand: 100V.
This is accomplished by the clamp introduced at
the bootstrap loader pin (12): this pin follows the
output voltage up to 100V and remains clamped
at 100V. This feature lets the output voltage
swing up to a gate-source voltage from the posi-
tive supply (V
voltage level.
load values (i.e. 16 Ohm).
The master chip connections are the same as
the normal single ones.
The outputs can be connected together with-
out the need of any ballast resistance.
The slave SGND pin must be tied to the nega-
tive supply.
The slave ST-BY pin must be connected to
ST-BY pin.
The bootstrap lines must be connected to-
gether and the bootstrap capacitor must be in-
creased: for N devices the boostrap capacitor
must be 22 F times N.
The slave Mute and IN-pins must be grounded.
S
40V the maximum Pout is 200W
-3 to 6V)