TS4855_04 Datasheet, PDF (22/27 Pages) STMicroelectronics – LOUDSPEAKER & HEADSET DRIVER WITH VOLUME CONTROL

TS4855
Application Information
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:
PSRR
=
20
× Log
 RMS


RMS
( Output
( Vripple
)
)



(dB )
Note: The measure of the Rms voltage is a Rms
selective measure with a bandpass equal to 1%
of the measured frequency .
6.8 Power-On Reset
When Power is applied to Vdd, an internal Power
On Reset holds the TS4855 in a reset state until
the Supply Voltage reached its nominal value.
The Power On reset has a typical threshold at
1.8V.
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