July 1994
4
Philips Semiconductors
Product specificiation
3 W BTL mono audio output amplifier with
DC volume control
TDA7056A
FUNCTIONAL DESCRIPTION
The TDA7056A is a mono BTL output amplifier with DC
volume control, designed for use in TV and monitor but
also suitable for battery-fed portable recorders and radios.
In conventional DC volume circuits the control or input
stage is AC coupled to the output stage via external
capacitor to keep the offset voltage low.
In the TDA7056A the DC volume stage is integrated into
the input stage so that coupling capacitors are not required
and a low offset voltage is maintained.
At the same time the minimum supply voltage remains low.
The BTL principle offers the following advantages:
•
lower peak value of the supply current
•
the frequency of the ripple on the supply voltage is twice
the signal frequency
Thus, a reduced power supply and smaller capacitors can
be used which results in cost savings.
For portable applications there is a trend to decrease the
supply voltage, resulting in a reduction of output power at
conventional output stages. Using the BTL principle
increases the output power.
The maximum gain of the amplifier is fixed at 35.5 dB. The
DC volume control stage has a logarithmic control
characteristic.
The total gain can be controlled from 35.5 dB to
−
44 dB.
If the DC volume control voltage is below 0.3 V, the device
switches to the mute mode.
The amplifier is short-circuit proof to ground, V
P
and
across the load. A thermal protection circuit is also
implemented. If the crystal temperature rises above
+
150
°
C the gain will be reduced, thereby reducing the
output power.
Special attention is given to switch-on and off clicks, low
HF radiation and a good overall stability.
LIMITING VALUES
In accordance with the Absolute Maximum System (IEC 134).
THERMAL RESISTANCE
Note to the thermal resistance
V
P
= 12 V; R
L
= 16
Ω
; The maximum sine-wave dissipation is = 1.8 W. The R
th vj-a
of the package is 55 K/W;
T
amb (max)
= 150
−
55 x 1.8 = 51
°
C
SYMBOL
PARAMETER
CONDITIONS
MIN.
MAX.
UNIT
V
P
supply voltage range
−
18
V
I
ORM
repetitive peak output current
−
1.25
A
I
OSM
non repetitive peak output current
−
1.5
A
P
tot
total power dissipation
T
case
<
60
°
C
−
9
W
T
amb
operating ambient temperature range
−
40
+85
°
C
T
stg
storage temperature range
−
55
+150
°
C
T
vj
virtual junction temperature
−
+150
°
C
T
sc
short-circuit time
−
1
hr
V
3
input voltage pin 3
−
8
V
V
5
input voltage pin 5
−
8
V
SYMBOL
PARAMETER
THERMAL RESISTANCE
R
th j-a
from junction to ambient in free air
55 K/W
R
th j-c
from junction to case
10 K/W
