1998 Sep 23
2
Philips Semiconductors
Product specification
4
25 W BTL quad car radio power
amplifier
TDA8568Q
FEATURES
Requires very few external components
High output power
Low output offset voltage
Fixed gain
Diagnostic facility (distortion, short-circuit and
temperature pre-warning)
Good ripple rejection
Mode select switch (operating, mute and standby)
Load dump protection
Short-circuit safe to ground and to V
P
and across the
load
Low power dissipation in any short-circuit condition
Thermally protected
Reverse polarity safe
Electrostatic discharge protection
No switch-on/switch-off plop
Flexible leads
Low thermal resistance
Pin compatible with the TDA8567Q, except for the gain.
GENERAL DESCRIPTION
The TDA8568Q is a integrated class-B output amplifier in
a 23-lead Single-In-Line (SIL) plastic power package.
It contains four amplifiers in BTL configuration, each with a
gain of 40 dB. The output power is 4
25 W in a 4
load.
APPLICATIONS
The device is primarily developed for car radio
applications.
QUICK REFERENCE DATA
ORDERING INFORMATION
SYMBOL
PARAMETER
CONDITIONS
MIN.
TYP.
MAX.
UNIT
V
P
operating supply voltage
6
14.4
18
V
I
ORM
repetitive peak output current
-
-
7.5
A
I
q(tot)
total quiescent current
-
230
-
mA
I
stb
standby current
-
0.2
100
A
I
sw
switch-on current
-
-
80
A
Z
i
input impedance
25
30
-
k
P
o
output power
THD = 10%
-
25
-
W
SVRR
supply voltage ripple rejection
R
s
= 0
-
45
-
dB
cs
channel separation
R
s
= 10 k
-
50
-
dB
G
v
closed loop voltage gain
39
40
41
dB
V
n(o)
noise output voltage
R
s
= 0
-
-
250
V
V
O
DC output offset voltage
-
-
200
mV
TYPE
NUMBER
PACKAGE
NAME
DESCRIPTION
VERSION
TDA8568Q
DBS23P
plastic DIL-bent-SIL power package; 23 leads (straight lead length 3.2 mm)
SOT411-1
1998 Sep 23
5
Philips Semiconductors
Product specification
4
25 W BTL quad car radio power
amplifier
TDA8568Q
FUNCTIONAL DESCRIPTION
The TDA8568Q contains four identical amplifiers which
can be used for bridge applications. The gain of each
amplifier is fixed at 40 dB.
Mode select switch (pin 15)
Standby: low supply current (<100
A)
Mute: input signal suppressed
Operating: normal on condition.
Since this pin has a low input current (<80
A), a low cost
supply switch can be applied.
To avoid switch-on plops, it is advised to keep the amplifier
in the mute mode during
150 ms (charging of the input
capacitors at pins 10, 11, 13 and 14). When switching
from standby to mute, the slope should be at least 18 V/s.
This can be realized by:
Microprocessor control
External timing circuit (see Fig.3).
Diagnostic output (pin 9)
D
YNAMIC
D
ISTORTION
D
ETECTOR
(DDD)
At the onset of clipping of one or more output stages, the
dynamic distortion detector becomes active and pin 9
goes LOW. This information can be used to drive a sound
processor or DC volume control to attenuate the input
signal and so limit the distortion. The output level of pin 9
is independent of the number of channels that are clipping
(see Fig.4).
S
HORT
-
CIRCUIT DIAGNOSTIC
When a short-circuit occurs at one or more outputs to
ground or to the supply voltage, the output stages are
switched off until the short-circuit is removed and the
device is switched on again, with a delay of approximately
10 ms after removal of the short-circuit. During this
short-circuit condition, pin 9 is continuously LOW.
When a short-circuit occurs across the load of one or more
channels, the output stages are switched off during
approximately 10 ms. After that time it is checked during
approximately 50
s to determine whether the short-circuit
is still present.
Due to this duty cycle of 50
s/10 ms the average current
consumption during this short-circuit condition is very low.
During this short-circuit condition, pin 9 is LOW for 10 ms
and HIGH for 50
s (see Fig.5). The protection circuits of
all channels are coupled. This means that if a short-circuit
condition occurs in one of the channels, all channels are
switched off. Consequently, the power dissipation in any
short-circuit condition is very low.
T
EMPERATURE PRE
-
WARNING
When the virtual junction temperature T
vj
reaches 145
C,
pin 9 goes LOW.
O
PEN COLLECTOR OUTPUTS
The diagnostic pin has an open collector output, so more
devices can be tied together. An external pull-up resistor is
needed.
Fig.3 Mode select switch circuitry.
handbook, halfpage
+
VP
MODE
MGD959
BZX79C/3.9V
10 k
47
F
Fig.4 Distortion detector waveform.
handbook, halfpage
V9
0
VP
Vo
0
t
MGG155
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