LA4905 查看數據表（PDF） - SANYO -> Panasonic

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LA4905

17-W, 2-Channel BTL AF High-Efficiency Power Amplifier for Car Stereo Systems

SANYO -> Panasonic 

LA4905

2. IC Internal Characteristics and Usage Notes

Switching Regulator

• To reduce power dissipation, the LA4905 includes a signal-following type switching regulator. When there is no input

signal, the self-excited oscillator operates at about 100 kHz.

• It is desirable for the amplifier block to be separated as far as possible from the tuner block to prevent interference from

extraneous radiation within the set. Also, when designing the printed circuit board layout, the pattern lines for the

switching regulator components should be made as short and as broad as possible.

• To prevent degradation of the characteristics of the LA4905 itself, the separation between the switching regulator

components and the IC input block (the input block pattern, the input capacitors, and the beep capacitor) should be at

least 1.5 cm.

Standby Function

• Pin 21 is the standby switch pin. The amplifier is turned

on by applying a voltage of about 3 V or higher through

an external resistor (R1).

• The value of R1 must be determined, using the following

formula, so that the pin 5 influx current remains under

500 µA if a voltage in excess of 13.2 volts is applied as

the standby switch voltage.

applied voltage – 1.4 V

R1 = ——————————

– 10 kΩ

500 µA

BEEP Pin (pin 4)

• If the BEEP pin is used, use a value for R102 shown in

the figure that is under 100 Ω and is as small as possible

to prevent degradation of the IC output noise voltage

(VNO).

Protection Circuits

• The LA4905 includes a built-in thermal protection

circuit to prevent destruction or degradation if the IC

generates abnormal amounts of heat. The thermal

protection circuit controls the IC so that the output is

gradually lowered if the IC junction temperature (Tj)

increases to about 160°C due to an insufficient heat sink

or other reason.

• The overvoltage protection circuit operates if the VCC

voltage exceeds a value of about 20 volts.

• Although the LA4905 includes an on-chip protection

circuit for shorts to VCC and shorts to ground, it does not

include a load shorted protection circuit. The idea behind

this design is that the thermal protection circuit will

protect the IC against load shorting. However, since load

shorting can also cause heating in external transistors and

coils, designs should take load shorting into

consideration.

Other Notes

• Pin 22 is an NC pin, and is not connected within the

package.

No. 5504-6/10

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