LA4631
External Components and Usage Notes
C1, C2 : These are input coupling capacitors; we recommend a value of 1µF or lower. The LA4631 input pin
potential is about 1.4V, and the polarity must be considered due to the DC potential of the circuits connected
to the LA4631 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 1µF
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 100µF. Amplifier impulse noise when
turned off (when the standby pin goes low) may be made worse if a value under 100µF is used. The pin 1
voltage is about 1/2V . A DC mute function can be applied if pin 1 is connected to ground through a 300 to
CC
500Ω resistor. Note that the muting activation voltage will be too low if a resistor value of 750Ω or higher is
used.
C4
C5
: This is an impulse noise prevention capacitor. The recommended value is 4.7µF. 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 10µF or higher is used, an "incomplete muting" phenomenon may occur when the
amplifier is turned off (when the standby pin goes low).
: 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 =
1/2πCout×R )
L
fc = low band cutoff frequency, Cout = C6, C7
• Caution
Although the LA4631 is basically pin compatible with the LA4632, there are certain differences in the external
components and the way the devices are used.
(Reference) Pin 5 IC internal equivalent circuit
R2
Rx Ix
STBY 2k
Ω
5
+
Standby
applied
Ix=max 4.5mA
voltage Vx
• The amplifier can be turned on or off by controlling the high/low state of pin 5.
• The amplifier is turned on by applying a voltage of 1.5V or higher or an influx current of 800µA or higher. (If a 5V
level is applied directly to pin 5, the pin 5 influx current will be about 4.5mA.)
• If a voltage, Vx, that exceeds 5V will be applied, insert a current limiter resistor (Rx) so that the influx current does
not exceed 4.5mA. (See the formula below.)
Rx = (Vx – 5V)/4.5mA
• When pin 5 is controlled by a microcontroller, to set up a pin 5 influx current (Ix) optimal for the drive capacity of
the microcontroller, calculate Rx from the following formula as a first approximation and measure the influx current
to verify that level.
Rx = (Vx/Ix) – R1 (2kΩ)
*: When a voltage is applied to the standby pin (pin 5), refer to the above and insert a resistor (Rx) to limit the influx
current if required.
No.8177-4/6
SANYO [ SANYO SEMICON DEVICE ]
