LA4631VC

No.A2051-4/7

External Components and Usage Notes

C1, C2 : These are input coupling capacitors; we recommend a value of 1

μF or lower. The LA4631VC input pin

potential is about 1.4V, and the polarity must be considered due to the DC potential of the circuits connected

to the LA4631VC front end. The amplifier's startup time (the time from the point power is first applied until

the point an output is generated) will change proportionally with the values of these input capacitors. (When

1

μF capacitors are used, the startup time will be about 0.2 seconds.)

C3

: This capacitor is used as a ripple filter. We recommend a value of 100

μF. Amplifier impulse noise when

turned off (when the standby pin goes low) may be made worse if a value under 100

μF is used. The pin 1

voltage is about 1/2VCC. A DC mute function can be applied if pin 1 is connected to ground through a 300 to

500

Ω resistor. Note that the muting activation voltage will be too low if a resistor value of 750Ω or higher is

used.

C4

: This is an impulse noise prevention capacitor. The recommended value is 4.7

μF. If a value of 2.2μF or lower

is used for C4, impulse noise when the amplifier is turned off (when the standby pin goes low) may be made

worse. Also, if a value of 10

μF or higher is used, an "incomplete muting" phenomenon may occur when the

amplifier is turned off (when the standby pin goes low).

C5

: Power supply capacitor. This capacitor should be located as close as possible to the IC (to minimize

increases in the power supply line impedance) to achieve stable amplifier operation.

C6, C7 : Output capacitors. These capacitors influence the amplifiers low band frequency characteristics. (fc =

1/2

πCout×RL)

fc = low band cutoff frequency, Cout = C6, C7

(Reference) Pin 5 Equivalent Circuit Inside IC

(Reference) Pin 5 IC internal equivalent circuit

Standby

applied

voltage Vx

+

Rx

Ix

Ix=max 4.5mA

5

STBY

R2

2k



• The amplifier can be turned on and off by controlling the level (high/low) of Pin 5.

• Applying a signal equal or greater than 1.5V and 800μA to Pin 5 turns on the amplifier. (If 5V is applied directly to

Pin 5 the inflow current od Pin 5 is approximately 4.5mA.)

• If a voltage, Vx, exceeding 5V is to be applied, current limiting resistor (Rx) should be inserted to limit the inflow

current to 4.5mA. (See following equation.)

Rx = (Vx – 5V)/4.5mA

• If Pin 5 is to be controlled by the microprocessor, the Pin 5 inflow current (Ix) should be optimized for the capacity

of the microprocessor by calculating Rx using the following equation, as a general guideline, and then confirming

the inflow current through sctual measurement.

Rx = (Vx/Ix) – R1 (2k

Ω)

Note: When apply voltage to standby (Pin 5), please add resistor (Rx).