LA9220M 查看數據表（PDF） - SANYO -> Panasonic

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LA9220M

Analog Signal Processor Circuit (ASP) for CD Players

SANYO -> Panasonic 

LA9220M

Description of Operation

· APC (auto laser power control)

This circuit controls the pickup laser power. The laser is turned on and off by commands from the microprocessor.

· RF amplifier (eye pattern output)

The pickup photodiode output current (A+C) is input to FIN2 (pin 1), and (B+D) is input to FIN1 (pin 2). The

current that is input is converted to the voltage, passes through the AGC circuit, and is then output from the RFSM

amplifier output RFSM (pin 41). The internal AGC circuit has a variable range of ±3dB, and the time constant can be

changed through the external capacitor connected to PH1 (pin 60). In addition, this circuit also controls the bottom

level of the EFM signal (RFSM output), and the response can be changed through the external capacitor connected to

BH1 (pin 61). The center gain setting for the AGC variable range is set by the resistance between RFSM (pin 41) and

RFS– (pin 42) ; if necessary, this resistance is also used for 3T compensation for the EFM signal.

· SLC (slice level control)

The SLC sets the duty ratio for the EFM signal that is input to the DSP to 50%. The DC level determined by integrat-

ing the EFMO signal output from the DSP to determine the duty ratio.

· Focus servo

The focus error signal is derived by detecting the difference between (A+C) and (B+D), which is (B+D) – (A+C),

and is then output from FE (pin 20). The focus error signal gain is set by the resistance between FE (pin 20) and FE–

(pin 21). The FA amplifier is the pickup phase compensation amplifier, and the equalizer curve is set by the external

capacitor and resistance. Furthermore, this amplifer has a mute function which is applied when VCC is turned on,

when the F-SERVO OFF command is sent, and during F-SEARCH. In order to turn the focus servo on, send either

the LASER ON command or the F-SERVO ON command.

The FD amplifier has a phase compensation circuit, a focus search signal composition function, and an offset cancel-

lation function. Focus seach is initiated by the F-SEARCH command, and a ramp waveform is generated by the

internal clock. This waveform is used for focus detection (focus zero cross) with the focus error signal and then turn

the focus servo on. The ramp waveform amplitude is set by the resistance between FD (pin 16) and FD– (pin 17).

Offset cancellation cancels the IC offset ; adjustment is started by the FOCUS-OFFSET ADJUST START command,

and is completed in about 250ms.

To cancel even the offset for the IV amplifier, etc., it is necessary to send the F-SERVO ON (LASER OFF) com-

mand. The FOCUS-OFFSET ADJUST OFF command is used to return to the state prior to offset cancellation.

· Tracking servo

The pickup phtodiode output current is input to E (pin 3) and F (pin 4). The current that is input is converted to the

voltage, passes through the balance adjustment VCA circuit and then the VCA circuit that follows the gain in the

RFAGC circuit, and is then output from TE (pin 7). The tracking error gain is set by the resistance between TE– (pin

6) and TE (pin 7).

The TH amplifier alters the servo response characteristics according to the THLD signal, etc., generated internally

after detection of the TGL signal from the DSP or the JP signal. When a defect is detected, the THLD mode goes into

effect internally. To avoid this, short DEF (pin 49) to L=GND. By inserting an external bandpass filter to remove the

shock component from the tracking error signal at SCI (pin 9), the gain is automatically boosted when a defect is

detected. The TOFF amplifier that is positioned immediately after TD (pin 13) functions to turn off the servo in

response to the TOFF signal from the DSP.

The TD amplifier performs servo loop phase compensation ; the characteristics are set by external CR. Furthermore,

this amplifer has a mute function, which is applied when VCC is turned on or the TRACK-SERVO OFF command is

issued. The muting function is released by the TRACK-SERVO ON command.

The TO amplifier has JP pulse composition function and a tracking offset cancellation function. The JP pulse is set

by JP (pin 14). (THLD detection is performed internally.) Offset cancellation is completed in about 30ms. The

TRACK-SERVO ON command and setting the TOFF pin (pin 35) low are required for offset cancellation.

Note : The LC78681KE TOFF ON/OFF command is valid only when disc motor control is in CLV mode. Accord-

ingly, tracking offset is cancelled in normal CLV mode. Note that when performed in STOP mode, external

control of the TOFF pin is required.

No.5188–7/20

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