VERY HIGH RDS DEMODULATION QUALITY
WITH IMPROVED DIGITAL SIGNAL PROC-
ESSING
HIGH PERFORMANCE, 57KHz BANDPASS
FILTER (8th ORDER)
PURELY DIGITAL RDS DEMODULATION
WITHOUT EXTERNAL COMPONENTS
ARI INDICATION AND RDS SIGNAL QUAL-
ITY OUTPUTS
4.332MHz CRYSTAL OSCILLATOR
(8.664 and 17.328MHz SELECTABLE OP-
TIONS)
LOW NOISE CMOS TECHNOLOGY
LOW RADIATION
DESCRIPTION
The
TDA7331,
an
improved
version
of
TDA7330B, recovers the additional inaudible
RDS information which is transmitted by FM radio
broadcasting stations and operates in accord-
ance with the EBU (European Broadcasting Un-
ion) specifications.
The device is made up of two sections: a cas-
caded antialiasing + switched capacitors band-
pass filter for precise RDS band selection and a
demodulating section that performs the extraction
od RDS data stream (RDDA) and clock (RDCL),
to be furher processed by a suitable RDS de-
coder.
Outputs for RDS signal quality and ARI indication
are also present.
February 1998
2nd ORDER
ANTIALIASING
FILTER
8th ORDER
SC-BANDPASS
FILTER
MPX
1
270pF
-
+
4
FILOUT
16
V
S
2
VREF
100nF
10
F
OSCILLATOR &
DIVIDER
57KHz PLL
FAST ARI
INDICATOR
POLARITY
BIPHASE DEC.
INTEGRAL
BIPHASE DEC.
1187.5Hz
PLL
MUX
0
1
DIFF. DECODER
TEST LOGIC
QUAL DET.
5
GND
N.C.
6,7,8,17
20
EXTRES
9
10
3
18
12
15
14
D97AU686B
TM
19
RDDA
13
QUAL
ARI
RDCL
FSEL
OSEL
OSCOUT
OSCIN
4.332MHz
C2 47pF
C1 27pF
11
T57
BLOCK DIAGRAM and TEST CIRCUIT
TDA7331
SINGLE CHIP RDS DEMODULATOR + FILTER
DIP20
SO20
ORDERING NUMBERS:
TDA7331
TDA7331D
1/7
MPX
VREF
OSEL
FILOUT
GND
N.C.
N.C.
N.C.
OSCOUT
1
3
2
4
5
6
7
8
9
RDCL
RDDA
QUAL
V
S
ARI
N.C.
FSEL
TM
EXTRES
20
19
18
17
16
14
15
13
12
D97AU687
OSCIN
10
T57
11
PIN CONNECTION
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
V
S
Supply Voltage
7
V
T
op
Operating Temperature Range
-40 to 85
C
T
stg
Storage Temperature
-55 to 150
C
PIN FUNCTION
N
o
pin
Name
Functional description
1
MPX
RDS input signal
2
VREF
Reference voltage
3
OSEL
Oscillator selector pin: - open, or closed to Vs = quartz oscillator
- closed to GND = external driven
4
FILOUT
Filter output
5
GND
Ground
6
nc
Not connected
7
nc
Not connected
8
nc
Not connected
9
OSCOUT
Oscillator output
10
OSCIN
Oscillator input
11
T57
Testing output pin: 57kHz clock output
12
RDCL
RDS clock output 1187.5Hz
13
RDDA
RDS data output
14
QUAL
Output for signal quality indication (High = good)
15
ARI
Output for ARI indication: - high when RDS+ARI are present
- high when only ARI is present
- low when only RDS is present
- undefined when nos signal is present
16
Vs
Supply voltage
17
nc
Not connected
18
FSEL
Frequency selector pin: - 100K to V
S
= 17.328MHz
- open = 4.332MHz
- closed to V
S
= 8.664MHz
19
TM
Test mode pin:
- open = normal operation
- closed to V
S
= testmode
20
EXTRES
Reset pin: - open = run mode
- closed to V
S
= reset condition
TDA7331
2/7
THERMAL DATA
Symbol
Description
DIP20
SO20
Unit
R
th j-amb
Thermal Resistance Junction-Ambient
Max
100
200
C/W
ELECTRICAL CHARACTERISTICS (T
amb
= 25
C, V
S
= 5V, unless otherwise specified).
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
V
S
Supply voltage
4.5
5
5.5
V
I
S
Supply current
7.5
11.0
mA
FILTER
f
C
Center frequency
56.5
57
57.5
kHz
BW
3dB Bandwidth
2.5
3
3.5
kHz
G
Gain
f = 57kHz
18
20
22
dB
A
Attenuation
f
4kHz
18
22
dB
f = 38kHz
50
60
dB
f = 67kHz
35
45
dB
R
I
Input impedance of MPX
80
120
150
K
R
L
Load impedance on FILOUT
1
M
S/N
Signal to noise ratio
V
IN
= 3mV
RMS
30
40
dB
V
IN
MPX input signal
f = 19kHz; T3
40dB(1)
f = 57kHz (RDS+ ARI)
1000
50
mV
RMS
mV
RMS
V
REF
Reference
V
S
/2
V
DEMODULATOR
Input pins (EXTRES, FSEL, TM)
all with internal pull down resistor
Input pin (OSEL)
with internal pull up resistor
I
PD
Input Current
V
IN
= 5V (pull-down input)
15
30
A
I
PU
Input Current
V
IN
= 0V (pull-up input)
-25
-10
A
V
IH
Input voltage high
0.7
V
S
0.8
V
S
V
V
IL
Input voltage low
0.2
V
S
0.3
V
S
V
Output pins (RDCL, RDDA, ARI, QUAL, T57)
V
OH
Ouput voltage high
I
L
= 0.5mA
4
4.6
V
V
OL
Output voltage low
I
L
= 0.5mA
0.4
1
V
OSCILLATOR
VCLL
Input level OSCIN pin
OSEL = open circuit
1
V
VCLH
Input level OSCIN pin
OSEL = open circuit
4
V
Amplitude OSCOUT
OSEL = open circuit
4.5
V
V
PP
Amplitude OSCIN
(for external drive)
OSEL = GND,
f = 4.332MHz
100
mVpp
OSEL = GND,
f = 8.664MHz
120
mVpp
OSEL = GND,
f = 17.328MHz
150
mVpp
(1) The 3rd harmonic (57kHz) must be less than -40dB with respect to the input signal plus gain.
TDA7331
3/7
OUTPUT TIMING
The RDS (1187.5Hz) output clock on RDCL line
is synchronized to the incoming data.
According to the internal PLL lock condition data
change can result on the falling or on the rising
clock edge. (see Fig. 1)
Whichever clock edge is used by the decoder
(rising or falling edge) the data will remain valid
for 416.7
sec after the clock transition.
OSCILLATOR CONTROLS (FSEL, OSEL)
Three different crystal frequencies can be used.
The adaption of the internal clock divider to the
external crystal is achieved via the input pin
FSEL. See the followings table for reference:
Crystal
FSEL (pin configuration)
4.332MHz
8.664MHz
17.328MHz
connected to GND or open
connected to Vs
external resistor of 100K to Vs
A special mode is introduced to reduce EMI. With
pin OSEL connected to GND the internal oscilla-
tor is switched off and an external sinusoidal fre-
quency could be applied on OSCIN. The peak to
peak voltage of this signal can be reduced down
to 60mV.
In this mode the frequency selection via FSEL is
still active.
Suggested values of C1 and C2 are shown in the
following table:
Crystal
C1
C2
4.332MHz
8.664MHz
17.328MHz
27pF
27pF
27pF
47pF
-
-
Figure 1. RDS timing diagram
CLOCK
LINE
DATA
LINE
TDA7331
4/7
DIP20 PACKAGE MECHANICAL DATA
DIM.
mm
inch
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
a1
0.254
0.010
B
1.39
1.65
0.055
0.065
b
0.45
0.018
b1
0.25
0.010
D
25.4
1.000
E
8.5
0.335
e
2.54
0.100
e3
22.86
0.900
F
7.1
0.280
I
3.93
0.155
L
3.3
0.130
Z
1.34
0.053
TDA7331
5/7
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