1996 May 14 5
Philips Semiconductors Product specification
40 W car radio high power amplifier TDA1560Q
FUNCTIONAL DESCRIPTION
The TDA1560Q contains a mono class-H BTL output
power amplifier. At low output power, up to 10 W, the
device operates as a normal BTL amplifier. When a larger
output voltage swing is required, the internal supply
voltage is lifted to approximately twice the external supply
voltage. This extra supply voltage is obtained from the
charge in the external electrolytic capacitors. Due to this
momentarily higher supply voltage, the maximum output
power is 40 W typical at a THD of 10%.
In normal use, when the output is driven with music-type
signals, the high output power is only required for a small
percentage of the time. Assuming a music signal has a
normal (Gaussian) amplitude distribution, the reduction in
dissipation is approximately 50% when compared to a
class-B output amplifier with the same output power.
The heatsink should be designed for use with music
signals.
If the device is continuous sine wave driven, instead of
driven with music signals and at a high output power
(class-H operation), the case temperature can rise above
120 °C with such a practical heatsink. In this event, the
thermal protection disables the high power supply voltage
and limits the output power to 10 W and the maximum
dissipation to 5 W.
The gain of each amplifier is internally fixed at 30 dB. With
the mode select input the device can be switched to the
following modes:
• Low standby current (<50 µA)
• Mute condition, DC adjusted
• On, operation in class-B, limited output power
• On, operation in class-H, high output power.
The device can be used as a normal BTL class-AB
amplifier if the electrolytic capacitors C1 and C2 are
omitted; see Fig.6. If the case temperature exceeds
120 °C, the device will switch back from class-H to class-B
operation. The high power supply voltage is then disabled
and the output power is limited to 10 W. By measuring the
voltage on the class-B/class-H pin, the actual crystal
temperature can be detected.
The open voltage on the class-B/class-H pin is related to
the global temperature of the crystal. By measuring this
voltage, external actions can be taken to reduce an
excessive temperature (e.g. by cutting off low frequencies
or externally switching to class-B). For the relationship
between the crystal temperature and the voltage on this
pin, see Fig.3.
By forcing a high voltage level on the class-B/class-H pin,
thereby simulating a high temperature, the device can be
externally switched to class-B operation. Similarly, by
forcing a low voltage level on the class-B/class-H pin,
thereby simulating a low temperature, the device can be
forced into class-H operation, even if the case temperature
exceeds 120 °C.
The device is fully protected against short-circuiting of the
outputs to ground or V
P
and across the load, high crystal
temperature and electrostatic discharge at all input and
output pins. In the event of a continuing short-circuit to
ground or VP, excessive dissipation is prevented because
the output stages will be switched off. The output stages
will be switched on again within 20 ms after the
short-circuit has been removed.
A diagnostic facility is available at pin 14. In normal
conditions the voltage at this pin will be the supply voltage
(VP). In the event of the following conditions:
• Junction temperature exceeds 150 °C
• Short-circuit of one of the outputs to ground or to V
P
• Load dump; VP>20V.
The voltage level at pin 14 will be at a constant level of
approximately1⁄2VP during fault condition. At a short-circuit
over the load, pin 14 will be at1⁄2VP for approximately
20 ms and VP for approximately 50 µs.