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 PACKAGE OPERATING TEMP. S1A0905-S0B0 16-SOP-225 -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 RSTB RDS DEMODULATOR TIN TEST XOSCI 8'th order SCF MUX Switched capacitor filter 2'nd Antialiasing Filter VDD Oscillator & Divider Smoothing filter & Comparator +5.0V 20pF 4.332MHz XOSCO BPSK Carrier Recovery Clock Recovery PLL 1.1875kHz VSS BPSK CLKO Recovered clock VREF Biphase Decoder VDDA BGR BIAS VSSA COMP 2 QUAL(High or Low) Differential Decoder DATAO 20pF Preliminary RDS DEMODULATOR IC S1A0905 PIN CONFIGURATION 16 SOP (TOP VIEW) 1 16 2 15 3 4 5 6 7 SEC S1A0905X01 QUAL DATAO VREF MUX VDDA VSSA SGND COMP 8 14 13 12 11 10 9 CLKO RSTB XOSCO XOSCI VDD VSS TIN TEST PIN DESCRIPTIONS Pin Name I/O Description 1 QUAL O Output for data quality indication (High = good data Low = bad data) 2 DATAO O RDS data output 3 VREF O System reference voltage output (2.5V) 4 MUX I Composite signal input 5 VDDA P Analog power (+5.0V) 6 VSSA P 7 SGND P System ground 8 COMP O Bandpass filter output 9 TEST I Test enable selecton pin (High = Test mode, Low = Normal mode) 10 TIN I Input signal for Test mode (Normally ground or open) 11 VSS P 12 VDD P 13 XOSCI I Xtal oscillator input 14 XOSCO O Xtal oscillator output 15 RSTB I Input for system reset (High = active mode, Low = reset mode) 16 CLKO O RDS clock output (1187.5Hz) Digital power(+5.0V) I: Input pin, O: Output pin, P: Power pin 3 Preliminary S1A0905 RDS DEMODULATOR IC ELECTRICAL CHARACTERISTICS Recommended Operating Conditions (Ta = 25°C) Parameter Symbol Min. Typ. Max. Unit Conditions Power supply voltage1 VDDA 4.5 5.0 5.5 V Analog power Power supply voltage2 VDD 4.5 5.0 5.5 V Digital power Electrical Characteristics (VDDA = 5.0V, Ta = 25°C, fosc = 4.332MHz) Parameter Symbol Min. Typ. Max. Unit Conditions Operating current Isum - 3.5 4.0 mA i(VDDA)+i(VDD) Reference voltage VREF 2.4 2.5 2.6 V Ouput high level Voh VDDA-1.0 VDDA-0.3 - V CLKO,DATAO,QUAL Output low level Vol - 0.2 1.0 V CLKO,DATAO,QUAL <Filter block> Center frequency Fc 56.5 57 57.5 kHz Gain GA 23 26 29 dB Fc=57kHz, MUXFILO Attenuation1 ATT1 -18 -22 - dB 57.0kHz4kHz Attenuation2 ATT2 -65 -80 - dB 38kHz Attenuation3 ATT3 -35 -50 - dB 67kHz S/N ratio SN 30 40 - dB 57kHz Vin=3mVrms Input level Vin 1 - 500 mVrms <Demodulator block> RDS detecter sensitivity SRDS - 0.5 1.0 mVrms RDS input level VRDS - - 300 mVrms DATA rate DRATE - 1187.5 - Hz Clock transient vs. DATA CT - 4.3 - us Lockup time(RDS) TL - 100 200 ms <Oscillator block> XTAL frequency Fosc - 4.332 - MHz Clock input high level Xosci 4.0 - - V Clock input low level Xosco - - 1.0 V Output Amplitude Xosc - 4.5 - Vpp Load capacitance CL - 20 - pF | 4 Preliminary RDS DEMODULATOR IC S1A0905 4.332MHz TEST APPLICATION 20pF O1 O7 20pF I3 I2 SW2 SW4 SW3 SW5 B A 5V B A B A A B 5V CLKO RSTB XOSCO XOSCI VDD VSS TIN 9 10 11 12 13 14 15 16 O6 TEST S1A0905X01 8 7 6 5 4 3 2 1 QUAL DATAO VREF MUX VDDA VSSA SGND COMP 10nF O4 A 5V 0.01uF 10uF O2 O3 SW1 B O5 14pF I1 Analog power Digital power 0.1uF 0.1uF 10uF 10uF Digital ground Analog ground :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