TS4621ML datasheet(32/40 Pages) STMICROELECTRONICS

32 / 40 page

Application information

TS4621ML

32/40

Doc ID 023181 Rev 1

The gain range in these configurations remains unchanged and is given by:

With reference to Figure 69, note that the absolute phase in the audio band is 180°.

4.4.1

Layout recommendations for single-ended operation

The connection location of each input that has to be set to ground is extremely important.

Incorrect connection location

Figure 70.

Incorrect ground connection for single-ended option

If these inputs are connected to AGnd (the ground of the TS4621ML class-G), the output

voltage can be expressed by the following simplified equation from an AC point of view.

Equation 1

Vout = Av x (Vaudio + Vmc + Vgndnoise) + Vbatnoise x PSRR

As shown in Equation 1, any ground noise and any parasitic AC voltage on Vmc is directly

multiplied by the gain of the amplifier. If Vmc can be totally controlled by the design of the

audio source device (no parasitic AC voltage), it is not necessarily the case for Vgndnoise.

This noise can be significantly reduced by an adequate low impedance ground plane, but

not totally eliminated. In practice, only ten millivolts in the right frequency range are enough

to produce an audible parasitic sound in the headphone with a volume level as low as

-20 dB.

VoutLR

VinLR

Gain

Rout

12 ohms min.

Rout

12 ohms min.

Cout

0.8 nF min.

Cout

0.8 nF min.

Cin

1 µF

Cin

1 µF

Cin

1 µF

Cin

1 µF

C12

2.2 µF

Css

2.2 µF

10 µF

3.3 µH

Vbat

Negative

supply

Positive

supply

AGnd

AVdd

InL-

InL+

InR+

InR-

VoutL

VoutR

CMS

Level

detector

Level

detector

HpVdd

PVss

Audio driver

Left output

Right output

Vgndnoise

VaudioL

VaudioR

Vmc

AM06154

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