TDA8931 Datasheet, PDF (20/31 Pages) NXP Semiconductors – Power comparator 1 X 20 W

Philips Semiconductors
TDA8931
Power comparator 1 × 20 W
To estimate the power dissipation, the following equation can be used:
P_d
=
P_o
×


η^-1--
–
1_
(6)
Where:
P_d = power dissipation
P_o = RMS output power (W)
η = efficiency of total application (0.91 for R_L = 8 Ω and 0.89 for R_L = 4 Ω)
The derating curves of the dissipated power as a function of ambient temperature for
several values of R_th(j-a) are illustrated in Figure 9. A maximum junction temperature
T_j = 150 °C is taken into account.
8
P_d
(W)
6
4
001aac303
R_th(j-a) (K/W)
20
25
30
35
40
2
0
25
50
75
100
T_amb (°C)
Fig 9. Derating curves for power dissipation as a function of maximum ambient
temperature
Example: TDA8931T mono amplifier, with substituting P_o = 1 × 20 W, R_th(j-a) = 24 K/W,
P_d = 2.47 W results in a junction temperature T_j(max) = 119 °C.
For this example the estimated maximum junction temperature at a high ambient
temperature of 60 °C for a mono amplifier driving 4 Ω speaker impedance stays below the
OTP threshold level of 150 °C.
9397 750 13847
Preliminary data sheet
Rev. 01 — 14 January 2004
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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