TDA7338
STEREO DECODER
INTEGRATED 19KHz SC NOTCH FILTER
FOR PILOT CANCELLATION
ON CHIP FILTER FOR PILOT DETECTOR
AND PLL
ADJUSTMENT FREE VOLTAGE CONTROL-
LED OSCILLATOR
AUTOMATIC PILOT DEPENDENT MONO/
STEREO SWITCHING
NOISE BLANKING WITH PROGRAMMABLE
THRESHOLD
HIGH CUT CONTROL AND STEREO BLEND
INTEGRATED HIGH PASS FILTER FOR IN-
TERFERENCE DETECTOR
LEVEL INPUT FOR ADDITIONAL SPIKE DE-
TECTION ON FIELDSTRENGHT SIGNAL
VERY HIGH SUPPRESSION OF HARMONIC
AND INTERFERENCE SIGNALS
DESCRIPTION
The TDA7338 is a new concept of monolithic inte-
grated stereo decoder with noise blanking for FM
car radio applications.
With the used BICMOS technique, the 19KHz
Notch Filter, the PLL Filter and Phase Filter is re-
alized on the chip with a Switched Capacitor con-
cept.
Avoiding the use of multipliers and non linear cir-
cuits a very high performance in terms of noise
suppression and total harmonic distortion is
reached.
December 1996
ORDERING NUMBER: TDA7338(DIP20)
TDA7338D( SO20)
SO20
DIP20
PIN CONNECTION (Top view)
1/11
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
V
CC
DC Supply Voltage
10.5
V
I
CC
Supply Current
20
mA
T
stg
Storage temperature
-55 to 150
C
T
amb
Operating ambient temperature
-40 to 85
C
THERMAL DATA
Symbol
Description
DIP 20
SO 20
Unit
R
thj-pins
Thermal resistance junction-pins
Typ
100
200
C/W
ESD
All pins are protected against ESD according to the MIL883 standard.
MPX
PILOT
DETECTOR
80KHz
LPF
DEMODULATOR
LEVEL
CONTROL
25KHz
LPF
19KHz
SC NOTCH
NOISE
BLANKER
HIGH
CUT
CONTROL
PEAK
DETECTOR
PULSE
FORMER
AMP
AMP
AMP
SC
PHASE
DETECTOR
&
PHASE
FILTER
DIVIDERS
VCO
140KHz
LPF
120KHz
LPF
AMP
PLL
TRIGGER
THRESHOLD
REFERENCE
20K
20K
CREF
IN L
OUT L
OUT R
IN R
HCR
HCL
MONO
PILOT
IND.
VR
VSB
VHCC
MPX IN
CSB456F11
VCO
2
6
1
7
8
3
5
VCO OFF
MUTE
TBLANK
PEAK
LEVEL
PROG
GND
V
S
D95AU364C
20
19
18
17
16
15
14
13
12
11
10
9
4
1
F
40.2K
1nF
1nF
70K
40.2K
40.2K
4.7
F
47nF
470pF
BLOCK DIAGRAM AND TEST CIRCUIT
TDA7338
2/11
ELECTRICAL CHARACTERISTICS (V
CC
= 9V; modulation frequency: 1KHz; de-emphasis time:
T = 50
s; nominal MPX input voltage: V
MPX
= 1.5V
PP
; m 100% (75KHz deviation, f
mod
= 1KHz);
R
IN
= 40.2k
, R
OUT
= 40.2k
; T
amb
= 27
C; C
REF
= 4.7
F; unless otherwise specified)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
V
CC
Supply Voltage
7.5
9
10.2
V
I
CC
Supply Current
5
10
15
mA
V
IN
MPX Input Level (peak to peak)
fm = 1KHz
1.5
V
V
ORMS
A.F. Output Voltage (mono)
pin 10 and 11V
IN
= 0.5V
RMS
MONO;
1.5
V
SVRR
Supply Voltage Ripple Rejection
V
RIPPLE
= 200mV; f = 1KHz
40
55
dB
V
L
/V
R
Difference of Output Voltage Levels
pin 10 and 11- mono
-0.8
0.8
dB
V
o
/V
i
Gain
V
10
/V
20
8.5
9.5
10.5
dB
R
O
Output Resistance
pin 10 and 11
10
50
V
O
DC Output Voltage
pin 10 and 11
4.2
4.5
4.8
V
Channel Separation
V
R
- V
SB
= -50mV
DC
30
45
dB
THD
Total Harmonic distortion
0.02
0.3
%
S
+
N
N
Signal plus noise to noise ratio
f = 20Hz to 16KHz;
S = 2Vrms
91
dB
M
Muting Attenuation
V
7
and V
8
< 0.6V
100
dB
V
DC
Mute DC Steps at pins 10, 11
Mute at pin 8
0
4
mV
CARRIER AND HARMONIC SUPPRESSION AT THE OUTPUT
19
Pilot Signal f = 19KHz
55
70
dB
38
Subcarrier f = 38KHz
75
dB
57
Subcarrier f = 57KHz
62
dB
76
Subcarrier f = 76KHz
90
dB
INTERMODULATION (note 1)
2
f
mod
= 10KHz; f
spur
= 1KHz
65
dB
3
f
mod
= 13KHz; f
spur
= 1KHz
75
dB
TRAFFIC RADIO (note 2)
57
Signal f = 57KHz
70
dB
SCA - SUBSIDIARY COMMUNICATIONS AUTHORIZATION (note 3)
67
Signal f = 67KHz
75
dB
ACI - ADJACENT CHANNEL INTERFERENCE (note4)
114
Signal f = 114KHz
95
dB
190
Signal f = 190KHz
84
dB
MONO/ STEREO SWITCH
V
INTH
Pilot Threshold Voltage
for stereo "ON"
12
20
28
mV
RMS
V
INTH
Pilot Threshold Voltage
for stereo "OFF"
7
14
21
mV
RMS
V
PI
Pilot Indicator Saturation Voltage
I = 1mA
0.2
0.5
V
I
PI
Pilot Indicator Leakage Current
V = 9V
10
A
V
19
Control Voltage for forced mono
= < 3dB
0.8
V
STEREO BLEND
V
16-17
Control Voltage for Channel
Separation
= 6dB; V
R
= 3.6V (note 5)
-0.31
-0.27
-0.23
V
V
16-17
Control Voltage for Channel
Separation
= 26dB;
-85
-55
-30
mV
TDA7338
3/11
ELECTRICAL CHARACTERISTICS (continued)
HIGH CUT CONTROL
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
deemp
De-Emphasis Time Constant
C
13
, C
14
= 1nF; V
15-17
= 50mV
43
50
57
s
R
15 -17
High Cut Control Resistance
V
15 - 17
= 50mV
43
50
57
K
R
15 -17
High Cut Control Resistance
V
15 - 17
= -0.5V (note 5)
115
150
185
K
VCO
f
osc
Oscillator Frequency
with Murata CSB456F11
456
KHz
f/f
Capture and Holding Range
1
%
V
VCO
V
CO OFF
Pin 7
0.6
V
NOISE INTERFACE DETECTOR (test condition: V
SB
> V
R
+ 50mV)
V
TR
Trigger Threshold (note 6)
V
PEAK
= 1.3V; PROG = GND
180
mV
V
PEAK
= 1.3V;
PROG = OPEN/V
DD
250
mV
V
TR
Trigger Threshold
V
PEAK
= 1.5V; PROG = GND
260
mV
V
PEAK
= 1.5V;
PROG = OPEN/V
DD
340
mV
T
S
Suppression Pulse Duration
C
BLANK
= 470pF
50
s
I
OS
Input Offset Current during
suppression time
10
pA
V
N1
V
PEAK
(pin 8)
V
IN
= 0mV
RMS
0.7
1.0
1.3
V
V
N2
V
PEAK
(pin 8)
V
IN
= 50mV
RMS
; f = 150KHz
1.1
1.5
2
V
V
N3
V
PEAK
(pin 8)
V
IN
= 100mV
RMS
; f = 150KHz
1.7
2.3
2.8
V
NOTES TO THE CHARACTERISTICS
1 INTERMODULATION SUPPRESSION
2
=
V
O
(
signal
) (
at1KHz
)
V
O
(
spurious
) (
at1KHZ
)
; f
s
= (2 x 10KHz) - 19KHz
3
=
V
O
(
signal
) (
at1KHz
)
V
O
(
spurious
) (
at1KHZ
)
; f
s
= (3 x 13KHz) - 38KHz
measured with : 91% mono signal; 9% pilot signal; fm=10KHz or 13KHz
2. TRAFFIC RADIO (V.F.) suppression
57
(
V.W.F.
)
=
V
O
(
signal
)
(
at1KHz
)
V
O
(
spurious
)
(
at
1
KHZ
23Hz
)
measured with : 91% stereo signal; 9% pilot signal; fm=1KHz; 5% subcarrier
(f=57KHz, fm = 23Hz AM, m = 60%)
3. SCA (SUBSIDIARY COMMUNICATIONS AUTHORIZATION)
67
=
V
O
(
signal
)
(
at
1KHz
)
V
O
(
spurious
) (
at9KHZ
)
; f
s
= (2 x 38KHz) - 67KHz
measured with : 81% mono signal; 9% pilot signal; fm=1KHz;
10% SCA - subcarrier (f
s
= 67KHz, unmodulated)
TDA7338
4/11
FUNCTIONAL DESCRIPTION
Signal Path
The TDA7338 Stereodecoder contains all neces-
sary functions for processing the MPX signal. Due
to the external input resistance (Pin 20) the circuit
can be adapted to different MPX input levels. Be-
hind a 80kHz lowpass filter the adjustment free
PLL for the pilot Tone is placed. The only external
component needed for the PLL is the ceramic
resonator for the oscillator which runs at 456kHz.
The pilot detector output is designed as an open
collector output, therefore an external pullup re-
sistor is needed. To force the decoder to "MONO"
Pin 19 has to be clamped to a voltage below
0.8V.
The voltage level (signal strength from the IF part)
applied to Pin 15 (VHCC) allows to control the
time constant of the deemphasis (nom. = 50
s,
see fig. 1). If the RF-signal is weak, the corner
NOTES TO THE CHZARACTERISTICS (continued)
4. ACI (ADJACENT CHANNEL INTERFERENCE)
114
=
V
O
(
signal
)
(
at
1
KHz
)
V
O
(
spurious
) (
at
4
KHZ
)
; f
s
= 110KHz - (3 x 38KHz)
190
=
V
O
(
signal
)
(
at
1
KHz
)
V
O
(
spurious
) (
at
4
KHZ
)
; f
s
= 186KHz - (5 x 38KHz)
measured with : 90% mono signal; 9% pilot signal; fm=1KHz; 1% spurious signal
(f
s
= 110KHz or 186KHz, unmodulated)
5. Control range typ 11% of V
R
(see figure 1 and figure2)
6. MEASUREMENT OF TRIGGER THRESHOLDS
All thresholds are measured by using a pulse
with T
R
= 2
s, T
HIGH
= 2
s, and T
F
= 10
s.
The repetition rate must not increase the PEAK
voltage.
VTR
Vin
DC
TR
THIGH
TF
Time
D95AU365
-0.5
-0.4
-0.3
-0.2
-0.1
0.0 V
HCC
-V
R
(V)
0
1
2
3.18
(=50
s)
f
c
(KHz)
VR
=3.6V
D95AU366
Figure 1: High Cut Control
-0.40
-0.32
-0.24
-0.16
-0.08 V
SB
-V
R
(V)
0
10
20
30
40
50
SEP
(dB)
V
R
=3.6V
D95AU367
Figure 2: Stereo Blend
TDA7338
5/11
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