CXA2568M 데이터 시트보기 (PDF) - Sony Semiconductor

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CXA2568M

RF Amplifier for CD Players

Sony Semiconductor 

CXA2568M

• APC

When the laser diode is driven by a constant current, the optical power output has extremely large negative

temperature characteristics.

The APC circuit is used to maintain the optical power output at a constant level.

The laser diode current is controlled according to the monitor photodiode output.

APC is set to ON by connecting the LD ON pin to VCC ; OFF by connecting it to VEE.

• 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 RFO 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 670 mV. (center voltage reference)

When the reference level is changed, connect the external resistor to the AGCVTH pin (Pin 2). The

reference level can be lowered by connecting the resistor between Pin 2 and the center output voltage or

between Pin 2 and VCC.

The AGCCONT pin (Pin 20) is used to switch the level of the laser power control circuit ; OFF, ON (laser

power limit of 40 %) and ON (laser power limit of 60 %).

The HOLD_SW pin (Pin 21) is used to switch the hold ON and OFF for the VL signal. Set this pin to ON so

as not to follow the fluctuation of the RF signal.

AGCCONT

L (VEE)

M (VC or OPEN)

H (VCC)

LPC

OFF

ON

ON

LPC limit

—

40 %

60 %

VL variable range

Approximately 1.27 V

Approximately 1.27 V±350 mV

Approximately 1.27 V±570 mV

—13—

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