TDA7576B datasheet(13/17 Pages) STMICROELECTRONICS

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TDA7576B

Power dissipation computation

Doc ID 023511 Rev 3

13/17

Power dissipation computation

The instantaneous power dissipated by each output stage is given by the formula below:

PD1,2(t) = 1/RL |VL1,2(t)| (Vcc/2 - |VL1,2(t)|)

with VL1,2(t) being the output signal on each of the two channels (VL1,2(t) = G * Vin1,2(t)).

If the two input signals are not identical, as seen in Section 4 a current IHVcc flows into or

out of the half Vcc buffer; this current causes dissipation within the HVcc buffer given by:

PDHVCC(t) = Vcc/(2RL) | VL2(t) - VL1(t) |

which is obviously 0 when the two channels have identical signals.

The total instantaneous power dissipation inside the TDA7576B is therefore given by:

Pdtot(t) = PD1(t) + PD2(t) + PDHVCC(t).

The dimensioning of the heat sink of the system must take into consideration these three

components.

For more details on power dissipation and recommendations on heat-sink characteristics

computation, please refer to the complete application note related to this subject.

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