Page 1
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
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Preliminary
RSTB
TEST
TIN
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
XOSCI
MUX
VSS
VREF
2'nd Antialiasing Filter
+5.0VVDD
8'th order
SCF
Switched capacitor filter
Smoothing filter & Comparator
Carrier
Recovery
BPSK
BPSK
Recovered clock
Oscillator &
Divider
Clock
Recovery
PLL
1.1875kHz
4.332MHz
XOSCO
CLKO
20pF
20pF
VDDA
VSSA
BGR
BIAS
Biphase
Decoder
COMP QUAL(High or Low)
Differential
Decoder
DATAO
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Preliminary
16 SOP
RDS DEMODULATOR IC S1A0905
PIN CONFIGURATION
(TOP VIEW)
QUAL
DATAO
VREF
MUX
VDDA
VSSA
SGND
COMP
1
2
3
4
5
6
7
8
SEC
S1A0905X01
16
15
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
Digital power(+5.0V)
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)
I: Input pin, O: Output pin, P: Power pin
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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
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Preliminary
RDS DEMODULATOR IC S1A0905
TEST APPLICATION
20pF
I3
4.332MHz
SW4
A B
5V
13
12
SW3
11
I2
B
10
SW2
A
9
TESTTINVSSVDDXOSCIXOSCORSTBCLKO
O1
16
20pF
SW5
5V
B
O7
15
A
O6
14
S1A0905X01
QUAL DATAO VREF MUX VDDA VSSA SGND COMP
1
2
3
4
5
6
7
8
O2 O3
O4
10uF
10nF
5V
0.01uF
I1
SW1
A
AB
B
O5
14pF
Analog power
Analog ground
:Input & Monitor Pin
B
A
0.1uF
:Switch
:Crystal oscillator
10uF
Digital power
0.1uF
Digital ground
*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
10uF
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Preliminary
S1A0905 RDS DEMODULATOR IC
NOTES
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