TDA8920C Datasheet, PDF (19/40 Pages) NXP Semiconductors – 2 X110 W class-D power amplifier

NXP Semiconductors
TDA8920C
2 × 110 W class-D power amplifier
13.5 Noise
Noise should be measured using a high-order low-pass filter with a cut-off frequency of
20 kHz. The standard audio band-pass filters used in audio analyzers, do not suppress
the residue of the carrier frequency sufficiently to ensure a reliable measurement of the
audible noise. Noise measurements should be carried out preferably using AES17
(‘brickwall’) filters or an audio precision AUX 0025 filter (designed specifically for
measuring class-D switching amplifiers).
13.6 Heatsink requirements
In many applications it may be necessary to connect an external heatsink to the
TDA8920C.
Equation 5 shows the relationship between the maximum power dissipation before
activation of TFB and the total thermal resistance from junction to ambient.
R_th(j–a) = ^T-----^j---^–---_P-^T----^a---^m----^b
(5)
Power dissipation (P) is determined by the efficiency of the TDA8920C. The efficiency
measured as a function of output power is given in Figure 21. Power dissipation can be
derived as a function of output power as shown in Figure 20.
30
P
(W)
(1)
20
mbl469
(2)
10
(3)
(4)
(5)
0
0
20
40
60
80
100
T_amb (°C)
(1) R_th(j-a) = 5 K/W.
(2) R_th(j-a) = 10 K/W.
(3) R_th(j-a) = 15 K/W.
(4) R_th(j-a) = 20 K/W.
(5) R_th(j-a) = 35 K/W.
Fig 9. Derating curves for power dissipation as a function of maximum ambient
temperature
TDA8920C_1
Preliminary data sheet
Rev. 01 — 29 September 2008
© NXP B.V. 2008. All rights reserved.
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