LC78621ED-E

Overview

The LC78621E is a CMOS LSI that implements the signal processing and servo control required by compact disk players, laser disks, CD-V, CD-I and related products. The LC78621E provides several types of signal processing, including demodulation of the optical pickup EFM signal, de-interleaving, error detection and correction, and digital filters that can help reduce the cost of CD player units. It also processes a rich set of servo system commands sent from the control microprocessor. It also incorporates an EFM-PLL circuit and a one-bit D/A converter.

Features

• 80-pin QIP (miniature, reduced space package)
• Silicon gate CMOS process (for low power)
• 5 V single-voltage power supply (for use in portable products)

Functions

• Input signal processing: The LC78621E takes an HF
signal as input, digitizes (slices) that signal at a precise
level, converts that signal to an EFM signal, and
generates a PLL clock with an average frequency of
4.3218 MHz by comparing the phases of that signal and
an internal VCO.
• Precise reference clock and necessary internal timing
generation using an external 16.9344 MHz crystal
oscillator
• Disk motor speed control using a frame phase difference
signal generated from the playback clock and the
reference clock
• Frame synchronization signal detection, protection and
interpolation to assure stable data readout
• EFM signal demodulation and conversion to 8-bit
symbol data
• Subcode data separation from the EFM demodulated
signal and output of that data to an external
microprocessor
• Subcode Q signal output to a microprocessor over the
serial I/O interface after performing a CRC error check
• Demodulated EFM signal buffering in internal RAM to
handle up to ±4 frames of disk rotational jitter
• Demodulated EFM signal reordering in the prescribed
order for data unscrambling and de-interleaving
• Error detection, correction, and flag processing (error
correction scheme: dual C1 plus dual C2 correction)
• The LC78620E sets the C2 flags based on the C1 flags
and a C2 check, and then performs signal interpolation
or muting depending on the C2 flags. The interpolation
circuit uses a quadruple interpolation scheme. The
output value converges to the muting level when four or
more consecutive C2 flags occur.
• Support for command input from a control
microprocessor: commands include track jump, focus
start, disk motor start/stop, muting on/off and track
count (8 bit serial input)
• Built-in digital output circuits.
• Arbitrary track counting to support high-speed data
access
• Zero cross muting
• Supports the implementation of a double-speed dubbing
function.
• D/A converter outputs with data continuity improved by
8× oversampling digital filters. (These filters function as
4× oversampling filters during double-speed playback.)
• Built-in third-order ∑∆ D/A converters (PWM output)
• Built-in digital attenuator (8 bits – alpha, 239 steps)
• Built-in digital de-emphasis
• Built-in digital level and peak meter functions
• Support for bilingual applications