Overview
The SM5904BF is a compression and non compression type shock-proof memory controller LSI for compact disc players. The compression level can be set in 4 levels, and external 4M DRAM can be connected to expand the memory to 4M bits. Digital attenuator, soft mute and related functions are also incorporated. It operates from a 2.4 to 3.3 V supply voltage range.

FEATUREs
- 2-channel processing
- Serial data input
     • 2s complement, 16-bit/MSB first, right-justified format
- Wide capture function (up to 3 × speed input rate)
- System clock input
     • 384fs (16.9344 MHz)
- Shock-proof memory controller
     • ADPCM compression method
     • 4-level compression mode selectable
        4-bit compression mode 2.78 s/Mbit
        5-bit compression mode 2.22 s/Mbit
        6-bit compression mode 1.85 s/Mbit
        Full-bit non compression mode 0.74 s/Mbit
     • External DRAM configurations usable
        2 × 4M DRAM (1M × 4 bits)
            Internal and External 4M DRAM
        1 × 4M DRAM (1M × 4 bits)
            Only Internal 4M DRAM
- Compression mode selectable
- Microcontroller interface
     • Serial command write and status read-out
     • Data residual detector: 15-bit operation, 16-bit output
     • Digital attenuator 8-bit setting
     • Soft attenuator function
        Noiseless attenuation-level switching (256- step switching in 23 ms max.)
     • Soft mute function
        Mute ON in 23 ms max.
        Direct return after soft mute release
     • Forced mute
- Extension I/O
    Microcontroller interface for external control using 4 extension I/O pins
- +2.4 to + 3.3 V operating voltage range
- Schmitt inputs
    All input pins (including I/O pins) except CLK (system clock)
- Reset signal noise elimination
    Approximately 3.8 µs or longer (65 system clock pulses) continuous LOW-level reset
- Digital audio interface (DIT)
- 44-pin QFP package (0.8 mm pin pitch)