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| Preliminary RDS DEMODULATOR IC S1A0905 GENERAL DESCRIPTION 16-SOP-225 THE OUTLINE OF RDS(RADIO DATA SYSTEM) Since 1988 most European national broadcaststations transmit RDScode beside their audio signals. RDS means Radio Data System and was originally intended to give people in their cars additional information about the weather or traffic(jams). But RDS has grown out to one big channel of information. Radiostations send their name, the time (with DCF-77 accuracy), their type of music (format) and even more. The digital data of RDS are multiplexed into an FM radio wave using a sub-carrier of 57kHz. The transmission rate of RDS data is 1.1875kbit/sec. The transmission rate of RDS data is 1.1875kbit/sec, and RDS data are encoded by differential encoding method. Then the encoded RDS data are modulated by BPSK using a clock of 1.1875kHz. The modulated RDS data is are modulated by carrier suppressed amplitude modulation using a subcarrier of 57kHz. And that signal are multiplexed into an FM radio wave. *RDS data are obtained by demodulating the received RDS modulation signal in RDS demodulator. First, the RDS modulation signal is extracted from an FM radio wave using a band pass filter. The BPSK signal is obtained from extracted RDS modulation signal by a 57kHz carrier recovery circuit. Then the bit rate clock of RDS data is extracted from the BPSK signal, and the BPSK signal is demodulated using the extracted clock signal. Then the RDS data are decoded by a differential decoding method using the demodulated BPSK signal. FEATURES * * * * * * * Low Current Two Stage Anti-aliasing Filter 8'th 57kHz Switched Capacitor Bandpass Filter DSB Demodulation (Carrier Recovery) Clock Recovery Circuit Biphase Decoder & Differential Decoder Quality Indication Output for Demodulated Data ORDERING INFORMATION DEVICE S1A0905-S0B0 PACKAGE 16-SOP-225 OPERATING TEMP. -40 - +85 1 Preliminary S1A0905 RDS DEMODULATOR IC DESCRIPTIONS The S1A0905 is a RDS demodulator. It recovers the RDS data which is transmitted by FM radio broadcasting. The device operates in accordance with the EBU(European Broadcasting Union) specifications. The IC includes a two stage antialiasing filter, a 57kHz switched capacitor bandpass filter, a comparator, a 57kHz carrier recovery circuit, a bit rate clock recovery circuit, BPSK decoder, differential decoding circuit, and RDS signal quality output. BLOCK DIAGRAM RDS DEMODULATOR RSTB TIN TEST XOSCI MUX 2'nd Antialiasing Filter 8'th order SCF Switched capacitor filter Smoothing filter & Comparator Oscillator & Divider BPSK Carrier Recovery BPSK Clock Recovery PLL 1.1875kHz Recovered clock 20pF 4.332MHz VDD VSS +5.0V XOSCO CLKO 20pF VREF Biphase Decoder VDDA BGR BIAS Differential Decoder DATAO VSSA COMP QUAL(High or Low) 2 Preliminary RDS DEMODULATOR IC S1A0905 PIN CONFIGURATION 16 SOP (TOP VIEW) QUAL DATAO VREF MUX VDDA VSSA SGND COMP 1 16 3 4 5 6 7 8 SEC S1A0905X01 2 15 14 13 12 11 10 9 CLKO RSTB XOSCO XOSCI VDD VSS TIN TEST PIN DESCRIPTIONS Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Name QUAL DATAO VREF MUX VDDA VSSA SGND COMP TEST TIN VSS VDD XOSCI XOSCO RSTB CLKO I/O O O O I P P P O I I P P I O I O Digital power(+5.0V) Xtal oscillator input Xtal oscillator output System ground Bandpass filter output Description Output for data quality indication (High = good data Low = bad data) RDS data output System reference voltage output (2.5V) Composite signal input Analog power (+5.0V) Test enable selecton pin (High = Test mode, Low = Normal mode) Input signal for Test mode (Normally ground or open) Input for system reset (High = active mode, Low = reset mode) RDS clock output (1187.5Hz) I: Input pin, O: Output pin, P: Power pin 3 Preliminary S1A0905 RDS DEMODULATOR IC ELECTRICAL CHARACTERISTICS Recommended Operating Conditions (Ta = 25C) Parameter Power supply voltage1 Power supply voltage2 Symbol VDDA VDD Min. 4.5 4.5 Typ. 5.0 5.0 Max. 5.5 5.5 Unit V V Conditions Analog power Digital power Electrical Characteristics (VDDA = 5.0V, Ta = 25C, fosc = 4.332MHz) Parameter Operating current Reference voltage Ouput high level Output low level Symbol Isum VREF Voh Vol Min. 2.4 VDDA-1.0 - Typ. 3.5 2.5 VDDA-0.3 0.2 Max. 4.0 2.6 1.0 Unit mA V V V Conditions i(VDDA)+i(VDD) CLKO,DATAO,QUAL CLKO,DATAO,QUAL 4 Preliminary RDS DEMODULATOR IC S1A0905 TEST APPLICATION 4.332MHz 20pF O1 O7 SW5 B 5V O6 16 15 14 A 20pF I3 I2 SW2 B A SW4 SW3 A B 5V B A 13 12 11 10 TIN CLKO RSTB XOSCO XOSCI VDD VSS TEST S1A0905X01 QUAL DATAO VREF MUX VDDA VSSA SGND COMP 1 2 3 4 5 6 7 10nF O4 5V 10uF O2 O3 0.01uF I1 Digital power A SW1 B O5 14pF Analog power 0.1uF Analog ground 8 9 10uF Digital ground 0.1uF 10uF :Input & Monitor Pin B A :Switch :Crystal oscillator *1: Digital power supply and Analog power supply are separated in the IC *2: It must have VDD (Digital power supply) of a sufficiently low impedence 5 Preliminary S1A0905 RDS DEMODULATOR IC NOTES 6 |
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