LA47510

No.8306-4/8

Description of Operation

1. Standby switch function (pin 4)

The Pin 4 threshold voltage is set to 2 VBE, and the amplifier turns on when Vst = 2.0 V or higher, and off when Vst

= 0.7 V or lower. In addition, Pin 4 requires an operating current of 40

µA or more.

Note: Do not ground the output with the Pin 4 voltage at approximately 1.4 V. In addition, do not give the Pin 4

voltage a time constant.

2. Mute function

Mute mode is established and the audio can be muted by connecting Pin 22 to GND through 10 k

Ω.

The mute time constant is determined by the external capacitor and resistor constants. The recommended external

constants are C = 3.3

µF, R = 10 kΩ.

3. Self-check function (loudspeaker burnout prevention)

Pin 25 is used to check, during normal operation, for any abnormality in the offset level of the amplifier and generates

a signal when an abnormal level is detected. Speaker burnout can be prevented by detecting this Pin 25 signal with a

microcontroller or other device and controlling the standby power supply, etc. (Output offset errors are thought to be

caused by the leak current of the input capacitor, etc.)

In addition, the Pin 25 signal can be turned off by setting Pin 1 to the GND potential.

4. Oscillation stability

Parasitic oscillation may be induced depending on the board layout.

Countermeasures against oscillation can be taken by adding the following parts.

Note that the following are only examples for reference, and that the optimum capacitance values must be confirmed

in the mounted condition for each set.

• Connect a Mylar capacitor (0.033

µF) between the BTL outputs.

• Connect a capacitor and a resistor (0.1 µF and 2.2

Ω in series) between each output and GND.

5. Sound quality (low frequencies)

The frequency response in the low frequency range can be improved by varying the capacitance value of the input

capacitor. The recommended value is 2.22

µF or less.

6. Shock noise

This IC incorporates a shock noise canceling circuit, and the shock noise canceling performance can be further

improved by using together with the mute function.

• When turning on the amplifier, turn the power supply and the mute function on at the same time.

Then turn the mute function off after the output current potential has stabilized.

• When turning off the amplifier, first turn the mute function off and then turn the power supply off.

7. Using the pin 25 function and the pin 1 off function

(1) Offset detection function (Pin 25)

Output offsets can be detected by directly monitoring the pin potential in the condition with 5 V applied through a

10 k

Ω resistor. When an offset is detected, the Pin 25 potential falls from 5 V to 0 V.

* The voltage level at pin 25 swings up and down in synchronization with the output signal when the LA47510 is

in the normal operating state.

(2) Offset detection function OFF switch (Pin 1)

The offset detection function (Pin 25) can be turned off by connecting Pin 1 to GND. Leave Pin 1 open during

normal operation.

8. Electric mirror noise suppression measures

Electric mirror noise can be reduced by inserting a bypass capacitor between the output and GND.

For reference, the standard value is approximately 470 pF and the maximum value is approximately 2200 pF.

However, note that inserting a bypass capacitor will cause the oscillation stability to worsen, so thorough

investigation of anti-oscillation measures should be made in the set condition before use.