LA4708N

No. A1783-5/9

Features of IC Inside and Usage Notes

Standby function

 Pin 5 is the standby switch pin. The amplifier is

turned on by applying approximately 2.5V or more

to this pin through an external resistor (R1).

 If voltage in excess of 13.2V is to be applied to the

standby switch, calculate the value of R1 using the

following formula so that the current flowing into

pin 5 is 500

A or less:

R1 =

10k

Mute function

 Pin 6 is the connector for the capacitor that determines the on time in order to prevent pop noise. By grounding this

pin, the amplifier can implement mute operation. In this case, the recovery time depends on C3.

How to reduce pop noise

 Although the LA4708N reduces pop noise, an electrolytic capacitor of between 0.47 and 2.2F can be connected

between pin 8 and the pre-GND to further reduce pop noise that occurs when power supply is turned on/off

(standby switch on/off). The larger the capacitance, the lower the frequency of pop noise, and it is barely audible,

but sound residue of the sound signal is liable to linger when power is turned off. Pin 8 is the bias pin for the output

amplifier and normally is left open.

Protectors

 In an output-to-ground and output-to-VCC short protector system configuration, if a DC resistor is connected

between amplifier output pin and GND, the protector may operate, causing the amplifier not to start operating.

Therefore, as a general rule, no DC resistor should be connected between amplifier output pin and GND.

 In order to prevent damage or degradation which may be caused by abnormally heated IC, the LA4708N has a thermal

shutdown protector. Accordingly, if the IC junction temperature (Tj) climbs to around 170 to 180

C due to inadequate

heat dissipation, the thermal shutdown protector will operate to control the output gradually into attenuation.

 Also be fully careful of handling other protectors built in the LA4708N.

Miscellaneous

 Since pins 1 and 9, which are unused, are connected internally, they must be left open.

 Pin 10 is an NC pin (no internal connection).

Applied voltage

1.4V

500

A