TS4962M datasheet(21/32 Pages) STMICROELECTRONICS

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TS4962M

Application Information

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Application Information

5.1

Differential configuration principle

The TS4962M is a monolithic fully-differential input/output class D power amplifier. The

TS4962M 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 full-differential amplifier are:

●

High PSRR (Power Supply Rejection Ratio).

●

High common mode noise rejection.

●

Virtually zero pop without additional circuitry, giving an faster start-up time compared to

conventional single-ended input amplifiers.

●

Easier interfacing with differential output audio DAC.

●

No input coupling capacitors required thanks to common mode feedback loop.

The main disadvantage is:

●

As the differential function is directly linked to external resistor mismatching, paying

particular attention to this mismatching is mandatory in order to obtain the best

performance from the amplifier.

5.2

Gain in typical application schematic

Typical differential applications are shown in Figure 1 on page 3.

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. For the remainder of this chapter, AVdiff will be referred to as AV for

simplicity’s sake.

Due to the tolerance of the internal 150k

Ω feedback resistor, the differential gain will be in the

range (no tolerance on Rin):

diff

Out

–

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

300

----------

273

----------

diff

327

----------

≤≤

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