TS4962 datasheet(30/44 Pages) STMICROELECTRONICS

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Application information

TS4962

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DocID10968 Rev 9

Application information

4.1

Differential configuration principle

The TS4962 is a monolithic, fully differential input/output class D power amplifier. The

TS4962 also includes a common-mode feedback loop that controls the output bias value to

average it at VCC/2 for any DC common-mode input voltage. This allows the device to

always have a maximum output voltage swing, and by consequence, maximize the output

power. Moreover, as the load is connected differentially compared to a single-ended

topology, the output is four times higher for the same power supply voltage.

The advantages of a fully differential amplifier are:

•

high PSRR (power supply rejection ratio).

•

high common mode noise rejection.

•

virtually zero pop without additional circuitry, giving a faster start-up time compared to

conventional single-ended input amplifiers.

•

easier interfacing with differential output audio DAC.

•

no input coupling capacitors required because of common-mode feedback loop.

The main disadvantage is that, since the differential function is directly linked to the external

resistor mismatching, particular attention should be paid to this mismatching in order to

obtain the best performance from the amplifier.

4.2

Gain in typical application schematic

Typical differential applications are shown in Figure 1 on page 6.

In the flat region of the frequency-response curve (no input coupling capacitor effect), the

differential gain is expressed by the relation:

with Rin expressed in kΩ.

Due to the tolerance of the internal 150 k

Ω feedback resistor, the differential gain is in the

range (no tolerance on Rin):

diff

Out

–

-------------------------------

300

----------

273

----------

Vdiff

327

----------

≤

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