Overview

The LC78624E is a CMOS LSI that implements the signal processing and servo control required by compact disc players. Including an EFM-PLL and text decoder, the LC78624E strictly limits functionality to basic signal processing and servo system operation to achieve the best cost-performance balance for low-end players. As basic functions, the LC78624E provides demodulation of the EFM signal from the optical pickup, de-interleaving, error detection and correction, and processes servo commands sent from the control microcontroller.

Features

• 64 pin QFP

• 5 V single-voltage power supply

Functions

• Input signal processing: The LC78624E 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 microcontroller

• Subcode Q signal output to a microcontroller over the serial I/O interface after performing a CRC error check (LSB first)

• Serial output to a microcontroller via the text decoder of the song titles and other text data stored in the Subcode R through W channels of the read-in area

• 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 LC78624E 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 dual-interpolation scheme. The previous value is held if the C2 flags indicate errors two or more times consecutively.

• Support for command input from a microcontroller: 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.

• Support for bilingual applications.

• General-purpose I/O ports: 5 pins