SILAN SC6579

Silan
Semiconductors SC6579
RADIO DATA SYSTEM (RDS)
DEMODULATOR
DESCRIPTION
The integrated CMOS circuit SC6579 is an RDS demodulator. It
recovers the additional inaudible RDS information which is
DIP-16
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).
SOP-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
ORDERING INFORMATION
• 57 kHz carrier regeneration
• Synchronous demodulator for 57 kHz modulated RDS signals
• Selectable 4.332/8.664 MHz crystal oscillator with variable
dividers
Device
Package
SC6579
DIP16-300-2.54
SC6579S
SOP-16-225-1.27
• 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.
PIN CONFIGURATION
QUAL
1
16 RDCL
RDDA
2
15 T57
14 OSCO
Vref
3
MUX
4
VDDA
5
VSSA
6
11 VSSD
CIN
7
10 TEST
SCOUT
8
9 MODE
SC6579
13 OSCI
12 VDDD
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
1
Rev: 1.0
2001.12.30
Silan
Semiconductors SC6579
BLOCK DIAGRAM
+5V
47pF
4.332/8.664MHz
82pF
0.1F
2.2K
OSCI OSCO
13
MPX
signal
MUX 4
330pF
antialiasing
filter
57kHz
bandpass
(8th order)
clocked
comparator
costas loop
variable and
fixed divider
reconstruction
filter
VDDD
12
14
quality bit
generator
1 QUAL
differential
decoder
2 RDDA
oscillator and
divider
SCOUT 8
560pF
CIN 7
VDDA 5
+5V
bi-phase
symbol
decoder
SC6579
16 RDCL
VP1
0.1F
Vref 3
reference
voltage
clock
regeneration
and sync
15 T57
test logic and output
selector switch
2.2F
6
9
VSSA
10
MODE
11
VSSD
TEST
Via pin MODE two different crystal frequencies can be used.
MODE
CRYSTAL CLOCK
LOW
4.332 MHz
HIGH
8.664 MHz
ABSOLUTE MAXIMUM RATINGS (Ta=25°C)
Symbol
Value
Analog Supply Voltage (pin 5)
Characteristic
VDDA
0~ 6
V
Digital Supply Voltage (pin 12)
VDDD
0~ 6
V
Vn
-0.5 ~ VDD + 0.5
V
Storage Temperature
Tstg
-40 ~+150
°C
Operating Ambient Temperature
Tamb
-40 ~+85
°C
±300 note 1
V
+1500 ~-3000 note 2
V
Voltage on All Pins; Grounds Excluded
Electrostatic Handling for All Pins Except
Pins 9 and 10
VESD
Unit
Notes1. Equivalent to discharging a 200 pF capacitor via a 0 Ω series resistor.
2. Equivalent to discharging a 100 pF capacitor via a 1.5 kΩ series resistor.
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0
2
2001.12.30
Silan
Semiconductors SC6579
ELECTRICAL CHARACTERISTICS
(VDDA =VDDD =5 V; Tamb =25°C and measurements taken in Fig.1; unless otherwise specified.)
Parameter
Symbol
Test condition
Min.
Typ.
Max.
Unit
Analog Supply Voltage (pin 5)
VDDA
3.6
5.0
5.5
V
Digital Supply Voltage (pin 12)
VDDD
3.6
5.0
5.5
V
6
D
mA
Total Supply Current
Itot
I5 +I12
Reference Voltage (pin 3)
Vref
VDDA = 5 V
D
D
2.5
D
V
1
--
--
mV
f = 5±2 kHz
200
--
--
mV
f < 50 kHz
1.4
--
--
V
f < 15 kHz
2.8
--
--
V
f > 70 kHz
3.5
--
--
V
MPX input (signal before the capacitor on pin 4)
RDS Amplitude (RMS value)
Maximum Input Signal Capability
(peak-to-peak value)
Vi MPX (rms)
Vi MPX (p-p)
∆f ±1.2 kHz RDS;
∆f ±3.5 kHz ARI; see Fig.5
Input Resistance
R4-6
f = 0 to 100kHz
40
--
--
kΩ
Signal Gain
G8-4
f = 57 kHz
17
20
23
dB
56.5
57.0
57.5
kHz
2.5
3.0
3.5
kHz
∆f =±7 kHz
31
--
--
dB
f < 45 kHz
40
--
--
dB
f < 20 kHz
50
--
--
dB
57 kHz band-pass filter
Center Frequency
fc
-3 dB Bandwidth
B
Stop Band Gain
Output Resistance (pin 8)
G
Tamb = -40 to +85 °C
f > 70 kHz
40
--
--
dB
Ro(8)
f = 57 kHz
--
26
--
Ω
Vi(rms)
f = 57 kHz
Comparator input (pin 7)
Minimum Input Level (RMS value)
Input Resistance
Ri
--
1
10
mV
70
110
150
kΩ
4.0
--
--
Oscillator input (pin 13)
HIGH-level Input Voltage
VIH
LOW-level Input Voltage
VIL
VDDD = 5.0 V
--
--
1.0
V
II
VDDD = 5.5 V
--
--
±C
µA
Input Current
VDDD = 5.0 V
V
To be continued
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0
3
2001.12.30
Silan
Semiconductors SC6579
(Continued)
Parameter
Symbol
Test condition
Min.
Typ.
Max.
Unit
Digital demodulator and outputs QUAL, RDDA, T57, OSCO and RDCL (pins 1, 2, 14, 15 and 16)
HIGH-level output voltage
VOH
IQ = -20 mA; VDDD = 4.5 V
4.4
--
--
V
LOW-level output voltage
VOL
IQ = 3.2 mA; VDDD = 5.5 V
--
--
0.4
V
--
1187.5
--
Hz
--
--
18
µs
--
57.0
--
kHz
VDDD = 4.5 V; V14 = 0.4 V
1.5
--
--
mA
Nominal Clock Frequency RDCL
fRDCL
Jitter of RDCL
∆tRDCL
Nominal Subcarrier Frequency T57
fT57
Output Current OSCO (pin 14)
note 1
VDDD = 4.5 V; V14 = 4.1 V
-1.6
--
--
mA
Output Current QUAL, RDDA, T57,
VDDD = 4.5 V; VO = 0.4 V
5.9
--
--
mA
RDCL (pins 1, 2, 15 and 16)
VDDD = 4.5 V; VO = 4.1 V
-5.3
--
--
mA
--
4.332
--
MHz
IO
4.332 MHz crystal parameters
XTAL Frequency
Maximum Permitted Tolerance
Adjustment Tolerance of f0
Load Capacitance
Resonance Resistance
f0
∆fmax
10 -6
±50
Tamb =25°C
--
--
±20
10 -6
Tamb = -40 to +85 °C
--
--
±25
10 -6
CL
--
30
--
pF
Rxtal
--
--
60
Ω
f0
--
8.664
--
MHz
∆fmax
--
±50
--
10 -6
Tamb =25°C
--
--
±30
10 -6
Tamb = -40 to +85 °C
--
--
±30
10 -6
CL
--
30
--
p
M F
Rxtal
--
--
60
Ω
∆fo
8.664 MHz crystal parameters
XTAL Frequency
Maximum Permitted Tolerance
Adjustment Tolerance of f0
Load Capacitance
Resonance Resistance
∆fo
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
4
2001.12.30
Silan
Semiconductors SC6579
PIN DESCRIPTION
Pin no.
Symbol
1
QUAL
Function
2
RDDA
3
Vref
Reference voltage output (0.5 VDDA )
4
MUX
Multiplex signal input
5
VDDA
+5 V supply voltage for analog part
6
VSSA
Ground for analog part (0V)
7
CIN
8
SCOUT
Subcarrier output of reconstruction filter
9
MODE
Oscillator mode/test control input
10
TEST
Test enable input
11
VSSD
Ground for digital part (0V)
12
VDDD
+5 V supply voltage for digital part
Quality indication output
RDS data output
Subcarrier input to comparator
13
OSCI
Oscillator input
14
OSCO
Oscillator output
15
T57
16
RDCL
57 kHz clock signal output
RDS clock output
QUICK REFERENCE DATA
SYMBOL
MIN.
TYP.
MAX.
UNIT
Analog Supply Voltage (pin 5)
3.6
5.0
5.5
V
VDDD
Digital Supply Voltage (pin 12)
3.6
5.0
5.5
V
Itot
Total Supply Current
--
6
--
mA
Vi(rms)
RDS Input Amplitude (RMS value; pin 4)
1
--
--
mV
VOH
HIGH-level Output Voltage for Signals
4.4
--
--
V
--
--
0.4
V
-40
--
+85
°C
VDDA
PARAMETER
RDDA, RDCL, QUAL and T57
VOL
LOW-level Output Voltage for Signals
RDDA, RDCL, QUAL and T57
Tamb
Operating Ambient Temperature
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
5
2001.12.30
Silan
Semiconductors SC6579
Filter part
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 µs after the clock transition. The timing of data change is 4 µs 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
6
2001.12.30
Silan
Semiconductors SC6579
TYPICAL RDS SENSITIVITY (BLOCK)
100
correct
blocks
(%)
75
(2)
(1)
50
25
0
10-1
1
Vi(RDS signal, RMS value)
(mV)
10
(1) RDS + ARI (BK)
(2) RDS only
TIMING DIAGRAM
RDCL
RDDA,
QUAL
4­s
842­s
421­s
4­s
MEH163
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0
7
2001.12.30
Silan
Semiconductors SC6579
APPLICATION CIRCUIT
82pF
16
15
14
4.332/8.664MHz
47pF
0.1­F
VDDD
13
12
11
10
9
6
7
8
SC6579
1
2
3
4
5
0.1­F
RDDA
RDCL
2.2­F
VDDA
560pF
330pF
MCU
MPX signal
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0
8
2001.12.30
Silan
Semiconductors SC6579
PACKAGE OUTLINE
DIP-16-300-2.54
UNIT: mm
7.62
6.35B0.25
0.25B0.05
2.54
1.52
3.00 MIN
3.86
4.36 MAX
+0.2
19.55 -0.3
1.27 MAX
0.99 +0.3
-0
1.52
0.460.08
+0.3
-0
SOP-16-225-1.27
UNIT:mm
0.40B0.10
5.0 +0.40
-0.20
0.50B0.20
6.0B0.4
3.90B0.3
1.80 MAX
1.27
8.89
10.15
0.20
+0.25
-0.20
+0.05
-0.02
HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD
Rev: 1.0
9
2001.12.30