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## TDA8922C Datasheet(PDF) 20 Page - NXP Semiconductors

 Part No. TDA8922C Description 2 X 75 W class-D power amplifier Download 40 Pages Scroll/Zoom 100% Maker NXP [NXP Semiconductors] Homepage http://www.nxp.com Logo

## TDA8922C Datasheet(HTML) 20 Page - NXP Semiconductors

 20 / 40 page TDA8922C_1© NXP B.V. 2009. All rights reserved.Product data sheetRev. 01 — 7 September 200920 of 40NXP SemiconductorsTDA8922C2× 75 W class-D power ampliﬁerIn the following example, a heatsink calculation is made for an 8Ω BTL application with a±30 V supply:The audio signal has a crest factor of 10 (the ratio between peak power and averagepower (20 dB)); this means that the average output power is 1⁄10 of the peak power.Thus, the peak RMS output power level is the 0.5 % THD level, i.e. 110 W.The average power is then 1⁄10 × 110W=11W.The dissipated power at an output power of 11 W is approximately 5 W.When the maximum expected ambient temperature is 50°C, the total Rth(j-a) becomesRth(j-a) = Rth(j-c) + Rth(c-h) + Rth(h-a)Rth(j-c) (thermal resistance from junction to case) = 1.5 K/WRth(c-h) (thermal resistance from case to heatsink) = 0.5 K/W to 1 K/W (dependent onmounting)So the thermal resistance between heatsink and ambient temperature is:Rth(h-a) (thermal resistance from heatsink to ambient) = 20 − (1.5 + 1) = 17.5 K/WThe derating curves for power dissipation (for several Rth(j-a) values) are illustrated inFigure 9. A maximum junction temperature Tj = 150 °C is taken into account. Themaximum allowable power dissipation for a given heatsink size can be derived, or therequired heatsink size can be determined, at a required power dissipation level; seeFigure 9.13.6 Pumping effectsIn a typical stereo single-ended conﬁguration, the TDA8922C is supplied by a symmetricalsupply voltage (e.g. VDD = 30 V and VSS = −30 V). When the ampliﬁer is used in an SEconﬁguration, a ‘pumping effect’ can occur. During one switching interval, energy is takenfrom one supply (e.g. VDD), while a part of that energy is returned to the other supply line(e.g. VSS) and vice versa. When the voltage supply source cannot sink energy, the voltageacross the output capacitors of that voltage supply source increases and the supplyvoltage is pumped to higher levels. The voltage increase caused by the pumping effectdepends on:• Speaker impedance• Supply voltage• Audio signal frequency• Value of supply line decoupling capacitors• Source and sink currents of other channelsPumping effects should be minimized to prevent the malfunctioning of the audio ampliﬁerand/or the voltage supply source. Ampliﬁer malfunction due to the pumping effect cantrigger UVP, OVP or UBP.15050–()5-------------------------20 K/W=