Digital signal processor SAA7706H for car audio. Reference data

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Digital signal processor SAA7706H for car audio. Reference data

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Encyclopedia of radio electronics and electrical engineering / Application of microcircuits

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The digital signal processor (DSP) SAA7706H from PHILIPS is designed for signal processing as part of a car audio system. The microcircuit is the central device around which peripheral components are assembled.

Among the many functions that the SA7706H provides, we highlight the main ones:

- suppression of signal distortion from the tuner caused by interference;
- stereo decoding for FM and AM modulation;
- demodulation of the RDS system signal;
- Dolby-B noise reduction system for the signal from the cassette deck;
- correction of the predistorted signal from the CD-drive;
- volume control, channel balance, sound positioning (front-rear) and dynamic range compression.

Some functions of the SAA7706H chip are implemented in hardware. These are interference suppression, FM stereo decoder and RDS demodulator.

The main feature of this chip (SAA7706H) is the ability to separate playback of signals from various sources through the front and rear stereo channels (for example, the driver of a car can listen to the radio, while the passengers in the back can listen to music from a CD).

To communicate with external digital signal processing devices (for example, an additional sound effects processor), the microcircuit (SAA7706H) provides two serial channels for digital data exchange (two input and two output channels of the I2S interface). In addition, the microcircuit (SAA7706H) has two SPDIF interface inputs.

The functions of the microcircuit are controlled by an external microcontroller via the I interface²C.

In addition, the chip (SAA7706H) provides and has:

- 5 sigma-delta analog-to-digital converters (ADC) of the 3rd order;
- 1 sigma-delta ADC of the first order;
- 4 digital-to-analog converters (DAC) with 128-fold oversampling;
- built-in filters of an output analog signal;
- simultaneous processing of radio range signals and audio range signals;
- digital FM stereo decoder;
- digital interference suppression in the FM signal;
- demodulation of the RDS signal using a separate ADC and the possibility of buffering the output data;
- two inputs with common mode suppression (mono) for voice signals (telephone, navigation system), mixing of speech signals to the front channel;
- two inputs with common mode suppression (stereo) for external signal sources (CD player, CD changer, etc.);
- input for a signal from a cassette deck;
- stereo input for a signal from an external AM stereo decoder;
- support for connecting an external signal coprocessor via the I2S interface;
- protection of outputs of a sound signal from short circuit;
- pin compatibility with SAA7705 and SAA7708 chips;
- digital inputs of the microcircuit are compatible with 5 V level signals;
- all analog inputs are protected from high-frequency pickups (for example, cell phones).

Program-controlled functions of the microcircuit:

- adjustment of volume levels, low and high frequencies, balance of stereo channels and rear / front;
- adjustment by 4-channel 5-band parametric equalizer;
- adjustment by a 9-band signal spectrum analyzer;
- control of a multifunctional tone generator (for the formation of telephone calls, etc.);
- a system for smoothing large differences in volume level;
- separate control of all signal parameters, as well as separate selection of signal sources for the front and rear channels;
- dynamic loudness system for low volume (loudness) and bass boost system;
- signal level monitoring;
- frequency response correction for a signal from a cassette deck and a phonogram search system;
- pre-emphasis correction for the signal from the CD-drive;
- mixing of speech signals (telephone, navigation system) with the main signal;
- digital stereo decoder (CQUAM) for AM-signal from the tuner (not for all versions of the chip software);
- digital interference suppression;
- mute the sound with a smooth decrease in the volume level (soft mute).

The microcircuit is produced in a QFP80 package.

In table. 1 shows the main parameters of the microcircuit, and in table. 2 - the purpose of its conclusions.

Table 1. Main operational parameters of the SAA7706H chip

Food
Supply voltage	3 ... 3,6
Current consumed by digital signal processing units, mA	no more 150
Current consumed by analog signal processing units (in the absence of signals at all inputs), mA	no more 60
Maximum power dissipation, mW	no more 750
Audio signal processing path from FM tuner (FM_MPX input)
Maximum input signal level, V	0,368
Level of non-linear distortion (input signal level 0,368 V), dB	no more than -65
Signal-to-noise ratio, dB	however 81
Processing path from other audio signal sources
Maximum input signal level, V	0,66
Level of non-linear distortion (input signal level 0,368 V), dB	no more than -75
Signal-to-noise ratio, dB	however 90
Output DAC parameters
The ratio of the sum of the levels of non-linear distortions and noise to the signal level, dB	no more than -85
Signal-to-noise ratio, dB	105
Quartz resonator frequency, MHz	11,2896

Table 2. Pin assignment of the SAA7706H chip

Pin number	Signal designation	Description
1	VDACP	Reference voltage for all ADC microcircuits
2	VDACN1	ADC1 common reference voltage
3	LEVEL	Adjusting the signal level from the tuner (FM or AM)
4	NAV_GND	Common mode suppression input (voice from navigation system)
5	POM	Turn-on delay input for output DACs. The delay time determines the capacitor connected to this input.
6	Rrv	Sound signal output (right channel, rear)
7	AUX_L	Audio signal input (left channel)
8	AUX_R	Audio signal input (right channel)
9	RLV	Audio signal output (left channel, rear)
10	V SSA2	Common output DAC and SPDIF interface circuitry
11	V DDA2	Power output DACs and SPDIF interface circuitry
12	VREFDA	Reference voltage of output DACs
13	FRV	Audio signal output (right channel, front)
14	CD_R_GND	Common mode suppression input, CD or cassette deck right channel
15	DSP2_INOUT2	Software configurable DSP2 status input/output (2)
16	FLV	Audio signal output (left channel, front)
17	DSP2_INOUT1	Software configurable DSP2 status input/output (1)
18	DSP2_INOUT3	Software configurable DSP2 status input/output (3)
19	DSP2_INOUT4	Software configurable DSP2 status input/output (4)
20	LOOPO	Clock output
21	TP1	The input is used only for testing the chip. In operation, can be connected to a common wire
22	V DDD3V7	Supply voltage input of interface circuits
23	V SSD3V7	Common interface circuits
24	SPDIF2	Input (1) of the SPDIF interface
25	SPDIF1	Input (2) of the SPDIF interface
26	SYSFS	Clock input
27	CD_WS	Serial line word select signal from CD-ROM drive
28	CD_DATA	Serial data line from CD drive
29	CD_CLK	Serial clock line from CD drive
30	IIS_CLK	Interface clock output I 2 S
31	IIS_IN1	I 1 S interface data input line 2
32	IIS_IN2	I 2 S interface data input line 2
33	IIS_WS	Interface word selection signal output I 2 S
34	IIS_OUT1	I 1 S interface data output line 2
35	IIS_OUT2	I 2 S interface data output line 2
36	V DDD3V6	Power supply for interface circuits
37	V SSD3V6	Common interface circuits
38	DSP1_IN1	Status input 1 for DSP1
39	DSP1_IN2	Status input 2 for DSP1
40	DSP1_OUT1	Status output 1 for DSP1
41	DSP1_OUT2	Status output 2 for DSP1
42	DSP_RESET	Initial reset signal. Active level? short
43	RTCB	Test block reset signal. Connected to common through internal terminating resistor
44	SHTCB	Test Block Clock
45	TSCAN	Test block control signal
46	V DDD3V5	Power supply for interface circuits
47	V SSD3V5	Common interface circuits
48	V DDD3V1	Power supply for interface circuits
49	V SSD3V1	Common interface circuits
50	V SSD3V2	Common interface circuits
51	V DDD3V2	Power supply for interface circuits
52	V DDD3V3	Power supply for interface circuits
53	V SSD3V3	Common interface circuits
54	V SSD3V4	Common interface circuits
55	V DDD3V4	Power supply for interface circuits
56	A0	I 2 C interface address selection input or test block serial data input
57	SCL	Bus clock I 2 C
58	SDA	Bus data line I 2 C
59	RDS_CLOCK	RDS data clock input/output
60	RDS_DATA	RDS serial data output
61	SEL_FR	FM_MPX input operation mode switching signal input
62	VSS(OSC)	Common clock generator
63	OSC_IN	Conclusion for connecting a quartz resonator
64	OSC_OUT	Conclusion for connecting a quartz resonator
65	VDD(OSC)	Clock power supply
66	AM_R/AM	Audio signal input (right channel) from AM tuner or signal from AM tuner if no external stereo decoder is available
67	AM_L/NAV	Audio input (left channel) from AM tuner or voice input from navigation system
68	TAPE_R	Cassette deck right channel audio input
69	TAPE_L	Cassette deck left channel audio input
70	CD_R	CD drive right channel audio input
71	PHONE	Common mode suppression input, phone voice
72	CD_L	Audio input for the left channel of the CD drive
73	PHONE_GND	Common mode suppression input, phone voice
74	V DDA1	Power supply for all ADCs
75	V SSA1	Common ADC and ADC3
76	VDACN2	ADC2 common reference voltage
77	CD_(L)_GND	Common mode suppression input, left channel from CD or cassette deck
78	VREFAD	Input/output, reference voltage of all ADCs
79	FM_RDS	RDS signal input from FM tuner
80	FM_MPX	FM tuner input

Author: Vladimir Zaitsev; Publication: remserv.ru

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