LA47202P Datasheet, PDF (4/8 Pages) Sanyo Semicon Device – Monolithic Linear IC Four-Channel BTL Power Amplifier for Car Audio Systems

Description of Operation
LA47202P
1. Standby switch function (pin 4)
The pin 4 threshold voltage is set to about 3 VBE.
The amplifier is turned ON at the application voltage of 3.0V or more and OFF at 0.5V or less.
2. Muting function (pin 22)
When pin 22 is set to the ground potential, the LA47202P goes to the muted state. This supports implementation of an
audio muting function.
The muting function is turned on when a level of 1V or lower is applied through a 10kΩ resistor, and the function is
turned off when this pin is open.
The muting time constant can be set with an external RC circuit.
3. Self diagnostics function (pin 25)
This function detects abnormal IC states, and outputs a signal from pin 25. Applications can prevent damage to
speakers and other problems by using a microcontroller to detect the pin 25 signal and control the standby switch
accordingly.
(1) Output short-circuit to VCC/ground : Pin 25 becomes LOW.
(2) Load short-circuit
: Pin 25 repeats HIGH and LOW states according to the output signal.
(3) Output offset abnormality
: Pin 25 goes low if the OUT pin (VN) voltage becomes lower than the
detection level. Problems that can cause an output offset abnormality
include input capacitor leakage and half shorts between the input pins and
adjacent circuit components.
Note that pin 25 is the NPN open collector output (active low). Keep pin 25 open-connection when not using.
4. CONTROL pin (pin 1)
The protective circuit response speed is adjusted by the pin 1 capacitor.
By adjusting the response speed of the protective circuit, abnormal sound generated when the protective circuit
operates at input of the large signal can be prevented.
When the capacitance value increases, abnormal sound is more difficult to be generated, but the response speed of the
protective circuit becomes lower. The capacitance value must be limited to maximum 0.01µF. The recommended
value is 4700pF.
Check the optimum value for each set.
As this is designed so that the protective circuit is activated when pin 1 has the GND potential, the protective circuit
becomes normally active when the capacitor is short-circuited.
5. AC GND pin (pin 16)
Be sure to use the pin 16 capacitor with the capacity the same as that of the input capacitor and connect it to PREGND
the same as that of the input capacitor.
6. Sound quality (low frequencies)
The frequency characteristics in low frequency range may be improved by varying the capacitance of input capacitor.
Note that this may cause influence on the shock noise, carry out confirmation with each set before varying the
capacitance value.
7. Impulse noise related systems
While the LA47202P does include an impulse noise prevention circuit, we recommend using the muting function
together with this circuit.
• When the amplifier is ON, turn ON the muting function simultaneously with power ON. When the output DC
potential has stabilized, turn OFF the muting function.
• When turning OFF the amplifier, first turn ON the muting function, then turn OFF power supply.
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