TS4621ML datasheet(33/40 Pages) STMICROELECTRONICS

33 / 40 page

TS4621ML

Application information

Doc ID 023181 Rev 1

33/40

Correct connection location

As shown in Figure 71, the best option is to route the single-ended signal in parallel with the

AC ground line of the other input. The AC grounded terminal must be routed in parallel to

the audio signal and grounded with the ground of the audio source.

Figure 71.

Correct ground connection for single-ended option

In this configuration, the AC output voltage is:

Equation 2

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

In Equation 2 the ground noise is attenuated by the performance of the CMRR. In practice,

50 dB of CMRR and ten millivolts for ground noise gives an output of approximately 30 µV,

which is normally too low to be perceptible in the headphone. If Vmc is also totally controlled

by the design of the audio source, Equation 2 becomes:

Equation 3

Vout = Av x Vaudio + Vbatnoise x PSRR

Like in differential mode, the main contributor for audio signal degradation is the AC noise

voltage on Vbat. Thanks to the TS4621ML’s very high PSRR that can attenuate GSM burst

noise, Equation 3 becomes:

Equation 4

Vout = Av x Vaudio

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

AM06155

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