Pioneer PD-R555RW Manuale di servizio - Pagina 30

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PDR-555RW, PDR-V500, PDR-19RW, PDR-509

control. The spindle motor is controlled by switching the above

three spindle servos (CAV, EFM-CLV and Wobble-CLV) and Stop

mode by controlling the switch of the servo amplifier IC (PA9004A,

IC247) according to the control signal output from the mechanism-

control microcomputer.

7.2 DEFECT CIRCUIT

The defect signal is output if there is a defect, such as a flaw, on the

disc. If the defect signal is "Hi," the tracking error is muted and the

low-frequency component of the error signal output just before the

defect occurs is applied to the focus error and the spindle error so

that the pliability rises.

7.3 EFM-DIGITAL PLL

Channel clocks are required to demodulate the EFM signal

reproduced from the optical system, because it is modulated to 3T

to 11T (where T is a cycle of the channel clock), which is integer

multiple of T. Practically, the PLL must read the channel clock

because the irregularities in the spindle rotation may change the

pulse width of the EFM signal.

This product has three stages of PLL. The first stage is a wide-

range PLL. The output of the first-stage PLL functions as the

standard for all clocks in CXD2585Q.

The PLL of the second stage is for generating high-frequency clock

indispensable for the digital PLL of the third stage.

The PLL of the third stage is a digital PLL for generating the practical

channel clock.

7.4 RF DETECTION

For CD-Rs there is an RF detection circuit to distinguish recorded

and unrecorded parts. The detection signal is output from the servo

amplifier IC (PA9004A, IC247-pin 61).

RFB and RFT also output the peak value and the bottom value of

the HF signal used for OPC operation.

7.5 MIRROR CIRCUIT

A mirror signal equivalent to that of conventional CD players is

used for CDs with EFM signals and for recorded parts of CD-Rs

and CD-RWs.

For unrecorded parts of a CD-R or CD-RW, the mirror signal peculiar

to the CD decoder is generated using the RC (radial contrast)

generated by crossing a groove.

7.6 AUDIO CIRCUITS

7.6.1 Analog Audio Input

The audio signal input via JA801 runs through the volume of the

VR Assy once and returns to the AUDIO Assy.

The input buffer circuit of IC803 (L-channel) and IC804 (R-channel)

is a single-ended/differential conversion circuit composed inverting-

inverting circuits.

The audio signal is converted to a differential signal and input to the

IC801 A/D converter (AK5340-VS).

7.6.2 A/D Converter

AK5340-VS, made by Asahi Chemical is used as the A/D converter.

This is an 18-bit, 2-channel A/D converter, which employs fifth-

generation delta-sigma techniques.

It contains two delta-sigma modulators and performs s 64-times

oversampling of both channels simultaneously.

The input range of the A/D converter is 4.0 Vp-p. So it becomes 0

dB when a signal of 2.08 Vp-p is input to input terminals AIN+ and

AIN-.

The control signals of the A/D converter are ADSTBY (pin 10),

ADLRCK (pin 14), ADBCLK (pin 15), and ADDATA (pin 16).

ADSTBY (pin 10) switches to Power-Down mode at "Hi" and offset

calibration begins upon falling from "Hi" to "Lo."

During the offset calibration, the input of each channel is measured

as the data for it. At this moment, each audio input terminal is

separated from the outside and short-circuited inside.

ADLRCK (pin 14) is the signal from the encoder IC (IC308

LC89585, pin 36), and ADBCLK (pin 15) and ADDATA (pin 16)

are signals for the encoder IC (pins 35 and 33).

ADBCLK

ADLRCK

ADDATA

MSB

L ch

Fig. 7-3 AK5340-VS data output timing

However, A/D Converter of PDR-509 uses PCM1800-1 made by

the BURR-BROWN company.

LSB

MSB

LSB

R ch