LA4815M

No.A1373-8/14

5. Popping noise reduction during power-off

The power supply line can be directly controlled ON and OFF without using the mute function. However, when using

a high supply voltage, the shock noise and aftersound during power-off tends to worsen. One method of coping with

this is to connect a capacitor between Pin 6 (VCC) and Pin 7 (MUTE) as shown in Fig. 9 so that the auto mute function

operates during power-off.

Recommended value = 1

µF

Figure 9

6. Input coupling capacitor (Cin)

Cin is an input coupling capacitor, and is used for DC cutting. However, this capacitor is also used to improve the ripple

rejection ratio, which changes according to the capacitance value (recommended value = 1

µF). In addition, this

capacitor also affects the transient response characteristics during power-on and when mute is canceled, so the constant

should be set in consideration of these characteristics.

Design reference value = approximately 0.33 to 3.3

µF

• Ripple rejection ratio : Increasing the capacitance value increases the rate, and reducing the value reduces the rate.

• Rise response speed : Increasing the capacitance value reduces the speed, and reducing the value increases the

speed.

• Popping noise : Increasing the capacitance value reduces the noise, and reducing the value increases the noise.

7. Output coupling capacitor (Cout)

Cout is an output coupling capacitor used for DC cutting. However, this capacitor, Cout, in combination with load

impedance RL forms a high-pass filter and attenuates the low frequency signal. Take into account the cutoff frequency

when determining the capacitance value. In addition, normally a chemical capacitor is used for this capacitor, but the

capacitance value of chemical capacitors decreases at low temperatures, so the value should be set in accordance with

this characteristic.

The cutoff frequency is expressed by the following formula.

fc = 1/(2

π × RL × Cout)

8. Output phase compensation capacitor (Cosc)

The Cosc capacitor is used to prevent output oscillation. Use a ceramic capacitor (recommended value = 0.1

µF) with

good high frequency characteristics, and locate this capacitor as close to the IC as possible.

9. Power supply capacitor (CVCC)

The CVCC capacitor is used to suppress the ripple component of the power supply line. Normally a chemical capacitor

(recommended value = 10

µF) is used for this capacitor. However, chemical capacitors have poor high frequency

characteristics, so when using a CPU, DSP or other IC that generates digital noise in the set, it is recommended that a

power supply bypass capacitor (ceramic capacitor, recommended value = approximately 0.1

µF) be added to reject

high-frequency components. Locate this bypass capacitor as close to the IC as possible.

+

+

Cmt

1

µF

CVCC

LA4815M

VCC

MUTE

6

7