CXA2550M Ver la hoja de datos (PDF) - Sony Semiconductor

Número de pieza

componentes Descripción

Fabricante

CXA2550M

RF Amplifier for CD Players

Sony Semiconductor 

CXA2550M/N

• LASER POWER CONTROL (LPC)

The RF level is stabilized by attaching an offset to the APC VL and controlling the laser power in sync with the

RF level fluctuations.

The RF O and RF I levels are compared and the larger of the two is smoothed by the RFTC's external CR.

This signal is then compared with the reference level.

The laser power is controlled by attaching an offset to VL according to the results of comparison with the

reference level.

Set the reference level to 670mV. (center voltage reference)

When the reference level is changed, connect the external resistor to the AGCVTH pin (Pin 1). The reference

level can be lowered by connecting the resistor between Pin 1 and the center output voltage or between Pin

20 and VCC.

The AGCCONT pin (pin 18) is used to switch the level of the laser power control circuit; OFF, ON (laser power

limit of 30%) and ON (laser power limit of 50%)

Note) For the laser power limit, 50% is recommended for PD IC; 30% for LC.

AGCCONT

H (VCC)

M (VC or OPEN)

L (VEE)

LPC

OFF

ON

ON

LPC limit

—

30%

50%

VL variable range

Approximately 1.27V

Approximately 1.27V ± 350mV

Approximately 1.27V ± 570mV

Notes on Operation

1. Power supply

The CXA2550M/N can be used either at dual power supply or single power supply. The table below shows the

connection of power supply for each case.

Dual power supply

Single power supply

VCC

+power supply

Power supply

VEE

–power supply

GND

VC

GND

OPEN

2. RF amplifier

In this circuit, the IC internal phase compensation value is set so as to support the voltage output-type pickup.

Therefore, when the current output-type pickup is used, the capacitance of optical pickup and leads etc. are

attached to PD1 and PD2 pins and oscillation may occur.

3. laser power control

The RF level is stabilized by attaching an offset to the APC VL and controlling the laser power in sync with the

RF level fluctuations. Therefore, use this circuit in the state where the focus servo is applied.

The laser life is shortened by increasing the laser power when the less light is reflected from the disc. It is

recommended that the typical laser power value is set lower to maintain the laser life.

Take care of the laser maximum ratings when using the laser power control circuit.

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