General information

STPA003

16/25

DS10473 Rev 2

5

General information

5.1

Operation

The STPA003's inputs are ground-compatible. If the standard value for the input capacitors

(0.22 µF) is adopted, the low frequency cut-off will amount to 16 Hz. For optimum pop

performances, the capacitor connected to AC-GND should be four times bigger than input

capacitors (see Figure 2).

Standby and mute pins are 3.3 V and 5 V compatible.

RC cells at both mute and stand-by pins have always to be used in order to smooth the

transitions for preventing any audible transient noise. A time constant slower than 2.5 V/ms

is suggested for the stand-by pin and 0.5 V/ms for the mute pin.

470 kΩ resistor.

The capacitance on SVR sets the start-up and shut-down times and helps to have pop-noise

free transitions. Its minimum recommended value is 10 µF. However, to have a fast start-up

time, the internal resistor on SVR pin, used to set the time constant, is reduced from 100 kΩ

capacitor on SVR is charged very quickly to VCC/4, as shown in the following figure.

Figure 21. SVR charge diagram

SVR pin accomplishes multiple functions:



it is used as a reference voltage for input pins (VCC/4)



the capacitor connected to SVR helps the supply voltage ripple rejection



it is used as a reference to generate the half supply voltage for the output

When the amplifier goes in stand-by mode or goes out from this condition, it is suggested to

put the amplifier in mute to ensure the absence of audible noise. Then the standby pin can

be set to the appropriate value (ground or > 2.2 V) and the capacitance on SVR pin is

discharged or charged consequently.

GAPGPS00673

Time