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Silan Semiconductors
RADIO DATA SYSTEM (RDS) DEMODULATOR
DESCRIPTION
The integrated CMOS circuit SC6579 is an RDS demodulator. It recovers the additional inaudible RDS information which is transmitted by FM radio broadcasting. The data signal RDDA and the clock signal RDCL are provided as outputs for further processing by a suitable decoder (microcomputer).
SC6579
DIP-16
FEATURES
* Anti-aliasing filter (2nd order) * Integrated 57 kHz band-pass filter (8th order) * Reconstruction filter (2nd order) * Clocked comparator with automatic offset compensation * 57 kHz carrier regeneration * Synchronous demodulator for 57 kHz modulated RDS signals * Selectable 4.332/8.664 MHz crystal oscillator with variable dividers * Clock regeneration with lock on bi-phase data rate * Bi-phase symbol decoder with integrate and dump functions * Differential decoder * Signal quality detector * Subcarrier output.
SOP-16
ORDERING INFORMATION
Device
SC6579 SC6579S
Package
DIP16-300-2.54 SOP-16-225-1.27
PIN CONFIGURATION
QUAL RDDA Vref MUX VDDA VSSA CIN SCOUT 1 2 3 4 5 6 7 8 16 RDCL 15 T57 14 OSCO
SC6579
13 OSCI 12 VDDD 11 VSSD 10 TEST 9 MODE
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2001.12.30
1
Silan Semiconductors
BLOCK DIAGRAM
SC6579
+5V 47pF 4.332/8.664MHz 82pF 2.2K OSCI OSCO 13 14 0.1F VDDD 12 quality bit generator 1 QUAL
MPX signal
MUX 4 330pF SCOUT 8 560pF CIN 7
antialiasing filter
57kHz bandpass (8th order)
reconstruction filter
oscillator and divider
clocked comparator VP1 reference voltage 6 VSSA
costas loop variable and fixed divider
+5V
VDDA 5 0.1F Vref 3
SC6579
bi-phase symbol decoder
differential decoder
2 RDDA
16 RDCL
clock regeneration and sync
test logic and output selector switch 9 MODE 10 TEST 11 VSSD
15 T57
2.2F
Via pin MODE two different crystal frequencies can be used.
MODE
LOW HIGH
CRYSTAL CLOCK
4.332 MHz 8.664 MHz
ABSOLUTE MAXIMUM RATINGS (Ta=25C)
Characteristic
Analog Supply Voltage (pin 5) Digital Supply Voltage (pin 12) Voltage on All Pins; Grounds Excluded Storage Temperature Operating Ambient Temperature Electrostatic Handling for All Pins Except Pins 9 and 10
Symbol
VDDA VDDD Vn Tstg Tamb VESD
Value
0~ 6 0~ 6 -0.5 ~ VDD + 0.5 -40 ~+150 -40 ~+85 300 note 1 +1500 ~-3000 note 2
Unit
V V V C C V V
Notes 1. Equivalent to discharging a 200 pF capacitor via a 0 series resistor. 2. Equivalent to discharging a 100 pF capacitor via a 1.5 k series resistor.
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2001.12.30
2
Silan Semiconductors
ELECTRICAL CHARACTERISTICS
SC6579
(VDDA =VDDD =5 V; Tamb =25C and measurements taken in Fig.1; unless otherwise specified.)
Parameter
Analog Supply Voltage (pin 5) Digital Supply Voltage (pin 12) Total Supply Current Reference Voltage (pin 3)
Symbol
VDDA VDDD Itot Vref
Test condition
Min.
3.6 3.6
Typ.
5.0 5.0 6
Max.
5.5 5.5
Unit
V V mA V
I5 +I12 VDDA = 5 V f 1.2 kHz RDS; f 3.5 kHz ARI; see Fig.5 f = 52 kHz

2.5
MPX input (signal before the capacitor on pin 4)
RDS Amplitude (RMS value) Vi MPX (rms) 1 200 1.4 2.8 3.5 40 17 ------20 ------23 mV mV V V V k dB
Maximum Input Signal Capability (peak-to-peak value)
Vi MPX (p-p)
f < 50 kHz f < 15 kHz f > 70 kHz
Input Resistance Signal Gain
R4-6 G8-4
f = 0 to 100kHz f = 57 kHz
57 kHz band-pass filter
Center Frequency -3 dB Bandwidth fc B f =7 kHz Stop Band Gain G f < 45 kHz f < 20 kHz f > 70 kHz Output Resistance (pin 8) Ro(8) f = 57 kHz Tamb = -40 to +85 C 56.5 2.5 31 40 50 40 -57.0 3.0 ----26 57.5 3.5 -----kHz kHz dB dB dB dB
Comparator input (pin 7)
Minimum Input Level (RMS value) Input Resistance Vi(rms) Ri f = 57 kHz -70 1 110 10 150 mV k
Oscillator input (pin 13)
HIGH-level Input Voltage LOW-level Input Voltage Input Current VIH VIL II VDDD = 5.0 V VDDD = 5.0 V VDDD = 5.5 V 4.0 ------1.0 V V A
To be continued
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2001.12.30
3
Silan Semiconductors
(Continued)
SC6579
Symbol
VOH VOL fRDCL tRDCL fT57 note 1 VDDD = 4.5 V; V14 = 0.4 V IO VDDD = 4.5 V; V14 = 4.1 V VDDD = 4.5 V; VO = 0.4 V VDDD = 4.5 V; VO = 4.1 V
Parameter
HIGH-level output voltage LOW-level output voltage Nominal Clock Frequency RDCL Jitter of RDCL Nominal Subcarrier Frequency T57 Output Current OSCO (pin 14) Output Current QUAL, RDDA, T57, RDCL (pins 1, 2, 15 and 16)
Test condition
IQ = -20 mA; VDDD = 4.5 V IQ = 3.2 mA; VDDD = 5.5 V
Min.
4.4 ----1.5 -1.6 5.9 -5.3
Typ.
--1187.5 -57.0 -----
Max.
-0.4 -18 ------
Unit
V V Hz s kHz mA mA mA mA
Digital demodulator and outputs QUAL, RDDA, T57, OSCO and RDCL (pins 1, 2, 14, 15 and 16)
4.332 MHz crystal parameters
XTAL Frequency Maximum Permitted Tolerance Adjustment Tolerance of f0 Load Capacitance Resonance Resistance f0 fmax fo CL Rxtal Tamb =25C Tamb = -40 to +85 C -----4.332 50 --30 -20 25 -60 -MHz 10 -6 10 -6 10 -6 pF
8.664 MHz crystal parameters
XTAL Frequency Maximum Permitted Tolerance Adjustment Tolerance of f0 Load Capacitance Resonance Resistance f0 fmax fo CL Rxtal Tamb =25C Tamb = -40 to +85 C ------8.664 50 --30 ---30 30 -60 MHz 10 -6 10 -6 10 -6 pF
Note1. The signal T57 has a phase lead of 123 (180) relative to the ARI carrier at output SCOUT.
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2001.12.30
4
Silan Semiconductors
PIN DESCRIPTION
Pin no.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
SC6579
Function
Symbol
QUAL RDDA Vref MUX VDDA VSSA CIN SCOUT MODE TEST VSSD VDDD OSCI OSCO T57 RDCL Quality indication output RDS data output Reference voltage output (0.5 VDDA ) Multiplex signal input +5 V supply voltage for analog part Ground for analog part (0V) Subcarrier input to comparator
Subcarrier output of reconstruction filter Oscillator mode/test control input Test enable input Ground for digital part (0V) +5 V supply voltage for digital part Oscillator input Oscillator output 57 kHz clock signal output RDS clock output
QUICK REFERENCE DATA
SYMBOL
VDDA VDDD Itot Vi(rms) VOH VOL Tamb
PARAMETER
Analog Supply Voltage (pin 5) Digital Supply Voltage (pin 12) Total Supply Current RDS Input Amplitude (RMS value; pin 4) HIGH-level Output Voltage for Signals RDDA, RDCL, QUAL and T57 LOW-level Output Voltage for Signals RDDA, RDCL, QUAL and T57 Operating Ambient Temperature
MIN.
3.6 3.6 -1 4.4 --40
TYP.
5.0 5.0 6 -----
MAX.
5.5 5.5 ---0.4 +85
UNIT
V V mA mV V V C
FUNCTION DESCRIPTION
The SC6579 is a demodulator circuit for RDS applications. It contains a 57 kHz bandpass filter and a digital demodulator to regenerate the RDS data stream out of the multiplex signal (MPX).
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2001.12.30
5
Silan Semiconductors
Filter part
SC6579
The MUX signal is band-limited by a second-order anti-aliasing-filter and fed through a 57 kHz band-pass filter (8th order band-pass filter with 3 kHz bandwidth) to separate the RDS signals. This filter uses switched capacitor technique and is clocked by a clock frequency of 541.5 kHz derived from the 4.332/8.664 MHz crystal oscillator. Then the signal is fed to the reconstruction filter to smooth the sampled and filtered RDS signal before it is output on pin 8. The signal is AC-coupled to the comparator (pin 7). The comparator is clocked with a frequency of 228 kHz (synchronized by the 57 kHz of the demodulator).
Digital part The synchronous demodulator (Costa's loop circuit) with carrier regeneration demodulates the internal coupled, digitized signal. The suppressed carrier is recovered from the two sidebands (Costa's loop). The demodulated signal is low-pass-filtered in such a way that the overall pulse shape (transmitter and receiver) approaches a cosinusoidal form in conjunction with the following Integrate and dump circuit. The data-spectrum shaping is split into two equal parts and handled in the transmitter and in the receiver. Ideally, the data filtering should be equal in both of these parts. The overall data-channel-spectrum shaping of the transmitter and the receiver is approximately 100% roll-off. The integrate and dump circuit performs an integration over a clock period. This results in a demodulated and valid RDS signal in form of bi-phase symbols being output from the integrate and dump circuit. The final stages of RDS data processing are the bi-phase symbol decoding and the differential decoding. After synchronization by data clock RDCL (pin 16) data appears on the RDDA output (pin 2). The output of the bi-phase symbol decoder is evaluated by a special circuit to provide an indication of good data (QUAL = HIGH) or corrupt data (QUAL = LOW).
Timing Fixed and variable dividers are applied to the 4.332/8.664 MHz crystal oscillator to generate the 1.1875 kHz RDS clock RDCL, which is synchronized by the incoming data. Which ever clock edge is considered (positive or negative going edge) the data will remain valid for 399 s after the clock transition. The timing of data change is 4 s before a clock change. Which clock transition (positive or negative going clock) the data change occurs in, depends on the lock conditions and is arbitrary (bit slip). During poor reception it is possible that faults in phase occur, then the clock signal stays uninterrupted, and data is constant for 1.5 clock periods. Normally, faults in phase do not occur on a cyclic basis. If however, faults in phase occur in this way, the minimum spacing between two possible faults in phase depends on the data being transmitted. The minimum spacing cannot be less than 16 clock periods. The quality bit changes only at the time of a data change.
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2001.12.30
6
Silan Semiconductors
TYPICAL RDS SENSITIVITY (BLOCK)
100 correct blocks (%) 75
SC6579
50
(1)
(2)
25
0 10-1 (1) RDS + ARI (BK) (2) RDS only 1 Vi(RDS signal, RMS value) (mV) 10
TIMING DIAGRAM
RDCL
RDDA, QUAL 4s 842s 421s MEH163
4s
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2001.12.30
7
Silan Semiconductors
APPLICATION CIRCUIT
4.332/8.664MHz 47pF 0.1F VDDD 13 12 11 10 9
SC6579
82pF 16 15 14
SC6579
1 2 2.2F 3 4 0.1F 5 VDDA 560pF 6 7 8
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2001.12.30
RDCL
RDDA
MCU
330pF MPX signal
8
Silan Semiconductors
PACKAGE OUTLINE
SC6579
UNIT: mm
0.25B0.05 1.52 7.62 GHJUHH 1.52 +0.3 -0 3.00 MIN 4.36 MAX 2.54
DIP-16-300-2.54
6.35B0.25
+0.2 19.55 -0.3
3.86
1.27 MAX
0.99 +0.3 -0
0.46f0.08
SOP-16-225-1.27
0.40B0.10 1.80 MAX
UNIT:mm
3.90B0.3
6.0B0.4
1.27 8.89 10.15 +0.25 -0.20 0.20 +0.05 -0.02
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0 2001.12.30
9
0.50B0.20
5.0 +0.40 -0.20

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