TS4855 datasheet(22/27 Pages) STMICROELECTRONICS

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TS4855

Application Information

22/27

6.6 Pop and Click performance

The TS4855 has internal Pop and Click reduction

circuitry. The performance of this circuitry is

closely linked with the value of the input capacitor

Cin and the bias voltage bypass capacitor Cb.

The value of Cin is due to the lower cut-off

frequency value requested. The value of Cb is

due to THD+N and PSRR requested always in

lower frequency.

The TS4855 is optimized to have a low pop and

click in the typical schematic configuration (see

page 2).

Note: The value of Cs is not an important

consideration as regards pop and click.

6.7 Notes on PSRR measurement

What is the PSRR?

The PSRR is the Power Supply Rejection Ratio.

The PSRR of a device, is the ratio between a

power supply disturbance and the result on the

output. We can say that the PSRR is the ability of

a device to minimize the impact of power supply

disturbances to the output.

How we measure the PSRR?

The PSSR was measured according to the

schematic shown in

Figure 57.

Figure 57: PSRR measurement schematic

Principles of operation

•

The DC voltage supply (Vcc) is fixed.

•

The AC sinusoidal ripple voltage (Vripple) is

fixed.

•

No bypass capacitor Cs is used.

The PSRR value for each frequency is:

Note: The measure of the Rms voltage is not an Rms

selective measure but a full range (20 Hz to

125 kHz) Rms measure. This means that the

effective Rms signal + the Noise is measured.

As the measurement is performed with a wide-

band frequency range apparatus, we have to

subtract the Noise part (quadratic operation) of

the measurement to obtain the real Rms signal

needed to calculate the PSRR, as shown in the

formula above.

)

(

RMS

Log

PSRR

)

Vripple

(

)

Output

(













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