TDA7577BLVPD datasheet(27/43 Pages) STMICROELECTRONICS

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DocID025375 Rev 5

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TDA7577BLV

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8.1

High efficiency introduction

Thanks to its operating principle, the TDA7577BLV obtains a substantial reduction of power

dissipation from traditional class-AB amplifiers without being affected by the massive

radiation effects and complex circuitry normally associated with class-D solutions.

The high efficiency operating principle is based on the use of bridge structures which are

connected by means of a power switch (Figure 1). The switch, controlled by a logic circuit

which senses the input signals, is closed at low volumes (output power steadily lower than

2.5 W) and the system acts like a "single bridge" with double load. In this case, the total

power dissipation is a quarter of a double bridge.

Due to its structure, the highest efficiency level can be reached when symmetrical loads are

applied on channels sharing the same switch.

Figure 36. High efficiency - basic structure

When the power demand increases to more than 2.5 W, the system behavior is switched

back to a standard double bridge in order to guarantee the maximum output power, while in

the 6 V start-stop devices the High Efficiency mode is automatically disabled at low VCC

(7.3 V ±0.3 V). No need to re-program it when Vcc goes back to normal levels.

In the range 2-4 W (@ VCC = 14.4 V), with the High Efficiency mode, the dissipated power

gets up to 50 % less than the value obtained with the standard mode.

TDA7577BLVPD Datasheet(PDF) 27 Page - STMicroelectronics