Philips Semiconductors
Car radio Digital Signal Processor (DSP)
Preliminary specification
SAA7705H
1 FEATURES
1.1 Hardware
• Three 3rd-order Switched Capacitor Analog-to-Digital
converters (SCADs)
• Digital-to-Analog Converters (DACs) with four times
oversampling and noise shaping
• Digital stereo decoder for the FM multiplex signal
• Improved digital Interference Absorption Circuit (IAC) for
FM
• Radio Data System (RDS) processing with an optional
16-bit buffer via a separate channel (two tuners
possible)
• Auxiliary high Common-Mode Rejection Ratio (CMRR)
analog CD input (CD-walkman, speech, economic
CD-changer, etc.)
• I2C-bus controlled
• Four channel 5-band I2C-bus controlled parametric
equalizer
• Two separate full I2S-bus and LSB-justified formats high
performance input interfaces
• Audio output short-circuit protected
• Separate AM left and right inputs
• Phase-Locked Loop (PLL) to generate the high
frequency DSP clock from a common fundamental
oscillator crystal
• Analog single-ended tape inputs
• I2S-bus subwoofer output (mono or stereo)
• Expandable with additional DSPs for sophisticated
features through an I2S-bus gateway
• Operating ambient temperature from −40 to +85 °C.
1.2 Software
• Improved FM weak signal processing
• Integrated 19 kHz MPX filter and de-emphasis
• Electronic adjustments: FM/AM level, FM channel
separation and Dolby level
• Baseband audio processing (treble, bass, balance,
fader and volume)
• Dynamic loudness or bass boost
• Audio level meter
• Tape equalisation (tape analog playback)
• Music Search System (MSS) detection for tape
• Dolby-B tape noise reduction
• Adjustable dynamics compressor
• CD de-emphasis processing
• Improved AM reception
• Soft audio mute
• AM IAC
• Pause detection for RDS updates
• Signal level, noise and multipath detection for AM/FM
signal quality information.
2 APPLICATIONS
• Car radio systems.
3 GENERAL DESCRIPTION
The SAA7705H performs all the signal functions in front of
the power amplifiers and behind the AM and FM multiplex
demodulation of a car radio or the tape input.
These functions are:
• Interference absorption
• Stereo decoding
• RDS decoding
• FM and AM weak signal processing (soft mute, sliding
stereo, etc.)
• Dolby-B tape noise reduction
• Audio controls (volume, balance, fader and tone).
Some functions have been implemented in the hardware
(stereo decoder, RDS decoding and IAC for FM multiplex)
and are not freely programmable. Digital audio signals
from external sources with the Philips I2S-bus format or the
LSB-justified 16, 18 or 20 bits format are accepted.
There are four independent analog output channels.
The channels have a hardware implemented 5-band
parametric equalizer, controlled via the I2C-bus.
1999 Aug 16
3