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ent. Fig. 17 shows this dissipable power as a
function of ambient temperaturefor different ther-
mal resistance.
MOUNTING INSTRUCTIONS
The power dissipated in the circuit must be re-
moved by adding an external heatsink.
Thanks
to
the
PENTAWATT
heatsink mounting operation is very simple, a
screw or a compression spring (clip) being suffi-
package, the
cient. Between the heatsink and the package is
better to insert a layer of silicon grease, to opti-
mize the thermal contact; no electrical isolation is
needed between the two surfaces. Fig. 18 shows
an exampleof heatsink.
Dimension suggestion
The following table shows the length that the
heatsink in fig. 18 must have for several values
of Ptot and Rth.
P
tot
(W)
Lenght of heatsink (mm)
R
th
of heatsink (
°
C/W)
12
60
4.2
8
6
40
6.2
30
8.3
Figure 18:
Example of heat-sink
Figure17:
Maximum Allowable Power Dissipa-
tion vs. Ambient Temperature
A.1 - MUSICPOWER CONCEPT
MUSIC POWER is (according to the IEC clauses
n.268-3 of Jan 83) the maximum power which the
amplifier is capable of producing across the rated
load resistance (regardless of non linearity) 1 sec
after the applicationof a sinusoidal inputsignal of
frequency1 KHz.
According to this definition our method of meas-
urementcomprises the followingsteps:
- Set the voltage supply at the maximum oper-
ating value;
- Applya input signal in the form of a 1KHztone
burst of 1 sec duration: the repetition period
of the signal pulses is 60 sec;
- The output voltageis measured1 sec from the
startof the pulse;
- Increasethe input voltage until the output sig-
nal showsa THD=10%;
- The music power is then V
2out
/RL, where
Vout is the output voltage measured in the
condition of point 4 and RL is the rated load
impedance;
The target of this method is to avoid excessive
dissipationin the amplifier.
A.2 - INSTANTANEOUS POWER
Another power measurement (MAXIMUM IN-
STANTANEOUS OUTPUT POWER) was pro-
posed by IEC in 1988 (IEC publication268-3 sub-
clause19.A).
We give here only a brief extract of the concept,
and a circuit useful for the measurement.
The supply voltage is set at the maximum operat-
ing value.
The test signal consists of a sinusoidal signal
whose frequency is 20 Hz, to which are added al-
ternate positive and negative pulses of 50
μ
s du-
ration and 500 Hz repetition rate. The amplitude
of the 20 Hz signal is chosen to drive the amplifier
to its voltageclipping limits, while theamplitudeof
the pulses takes the amplifier alternately into its
current-overloadlimits.
APPENDIX A
TDA2050
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