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TDA8947J Datasheet(Fiches technique) 18 Page - NXP Semiconductors

 Numéro de pièce TDA8947J Description 4-channel audio amplifier (SE: 1 W to 25 W; BTL: 4 W to 50 W) Télécharger 24 Pages Scroll/Zoom 100% Fabricant PHILIPS [NXP Semiconductors] Site Internet http://www.nxp.com Logo

 18 page Philips SemiconductorsTDA8947J4-channel audio ampliﬁerPreliminary dataRev. 01 — 06 February 200418 of 249397 750 10779© Koninklijke Philips Electronics N.V. 2004. All rights reserved.13.3 Thermal behavior and heatsink calculationThe measured maximum thermal resistance of the IC package, Rth(j-mb), is 1.3 K/W.A calculation for the heatsink can be made, with the following parameters:Tamb(max) =60 °C (example)VCC = 18 V and RL =4 Ω (SE)Tj(max) = 150 °C (speciﬁcation)Rth(tot) is the total thermal resistance between the junction and the ambient includingthe heatsink. This can be calculated using the maximum temperature increasedivided by the power dissipation:Rth(tot) =(Tj(max) − Tamb(max))/PDAt VCC =18V and RL =4 Ω (4 × SE) the measured worst-case sine-wave dissipationis 17 W; see Figure 9. For Tj(max) = 150 °C the temperature raise, caused by thepower dissipation, is: 150− 60=90 °C:P× Rth(tot) =90 °CRth(tot) = 90/17 = 5.29 K/WRth(h-a) =Rth(tot) − Rth(j-mb) = 5.29 − 1.3 = 3.99 K/WThis calculation is for an application at worst-case (stereo) sine-wave output signals.In practice music signals will be applied, which decreases the maximum powerdissipation to approximately half of the sine-wave power dissipation of 9 W (seeSection 8.2.2). This allows for the use of a smaller heatsink:P× Rth(tot) =90 °CRth(tot) = 90/9 = 10 K/WRth(h-a) =Rth(tot) − Rth(j-mb) =10 − 1.3 = 8.7 K/W