TDA7338
STEREO DECODER
1
■
FEATURES
INTEGRATED 19KHz SC NOTCH FILTERFOR
PILOT CANCELLATION
ON CHIP FILTER FOR PILOT DETECTOR
AND PLL
ADJUSTMENT FREE VOLTAGE
CONTROLLED OSCILLATOR
AUTOMATIC PILOT DEPENDENT MONO/
STEREO SWITCHING
NOISE BLANKING WITH PROGRAMMABLE
THRESHOLD
HIGH CUT CONTROL AND STEREO BLEND
INTEGRATED HIGH PASS FILTER FOR
INTERFERENCE DETECTOR
LEVEL INPUT FOR ADDITIONAL SPIKE
DETECTION ON FIELDSTRENGHT SIGNAL
Figure 1. Package
■
SO20
■
Table 1. Order Codes
Part Number
TDA7338D
TDA7338D013TR
■
■
■
2
DESCRIPTION
■
■
VERY HIGH SUPPRESSION OF HARMONIC
AND INTERFERENCE SIGNALS
Figure 2. reached.Block Diagram
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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 realized on the chip with a
Switched Capacitor concept. Avoiding the use of
multipliers and non linear circuits a very high per-
formance in terms of noise suppression and total
harmonic distortion is
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April 2005
Rev. 9
1/12
TDA7338
Table 2. Absolute Maximum Ratings
Symbol
V
CC
I
CC
T
stg
T
amb
DC Supply Voltage
Suply Current
Storage Temperature
Operating AmbientTemperature
Parameter
Value
10.5
20
-55 to 150
-40 to 85
Unit
V
mA
°C
°C
Table 3. Thermal Data
Symbol
R
th j-pins
Parameter
Thermal resistance junction-pins
Value
200
Unit
Figure 3. Block Diagram and Test Circuit
40.2K
1µF
MPX
PILOT
IND.
18
MPX IN
20
MONO
19
VR
17
VSB
16
VHCC
15
70K
AMP
PILOT
DETECTOR
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PLL
SC
PHASE
DETECTOR
&
PHASE
FILTER
VCO
CSB456F11
80KHz
LPF
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DEMODULATOR
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LEVEL
CONTROL
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1nF
HCL
14
13
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1nF
HCR
12
IN R
40.2K
20K
AMP
11
OUT R
HIGH
CUT
CONTROL
25KHz
LPF
19KHz
SC NOTCH
NOISE
BLANKER
20K
AMP
10
OUT L
40.2K
9
IN L
AMP
DIVIDERS
PEAK
DETECTOR
PULSE
FORMER
VCO
140KHz
LPF
120KHz
LPF
TRIGGER
THRESHOLD
REFERENCE
4
CREF
4.7µF
2
6
LEVEL
1
PROG
TBLANK
470pF
VCO OFF
7
8
PEAK
47nF
MUTE
3
GND
V
S
5
D95AU364C
2/12
TDA7338
3
ELECTRICAL CHARACTERISTCS
Table 4.
(V
CC
= 9V; modulation frequency: 1KHz; de-emphasis time: T = 50µs; nominal MPX input voltage:
V
MPX
= 1.5V
PP
; m 100% (75KHz deviation, f
mod
= 1KHz); R
IN
= 40.2kΩ, R
OUT
= 40.2kΩ;
T
amb
= 27°C; C
REF
= 4.7µF; unless otherwise specified)
Symbol
V
CC
I
CC
V
IN
V
ORMS
SVRR
V
L
/V
R
V
o
/V
i
R
O
V
O
α
THD
S
+
N
-------------
-
N
α
M
V
DC
α19
α38
α57
α76
α2
α3
α57
α67
Parameter
Supply Voltage
Supply Current
MPX Input Level (peak to peak)
A.F. Output Voltage (mono)
Supply Voltage Ripple Rejection
Difference of Output Voltage
Levels
Gain
Output Resistance
DC Output Voltage
Channel Separation
Total Harmonic Distortion
Signal plus noise to noise ratio
Muting Attenuation
Mute DC Steps at pins 10, 11
Pilot Signal f = 19KHz
Subcarrier f = 38KHz
Subcarrier f = 57KHz
Subcarrier f = 76KHz
f
m
= 1KHz
pin 10 and 11V
IN
= 0.5V
RMS
MONO;
V
RIPPLE
= 200mV; f = 1KHz
pin 10 and 11- mono
V
10
/V
20
pin 10 and 11
pin 10 and 11
V
R
- V
SB
= -50mV
DC
f = 20Hz to 16KHz; S = 2Vrms
V
7
and V
8
< 0.6V
Mute at pin 8
4.2
40
-0.8
8.5
9.5
Test Condition
Min.
7.5
5
Typ.
9
10
1.5
1.5
55
0.8
Max.
10.2
15
Unit
V
mA
V
V
dB
CARRIER AND HARMONIC SUPPRESSION AT THE OUTPUT
INTERMODULATION
(note 1)
TRAFFIC RADIO
(note 2)
SCA - SUBSIDIARY COMMUNICATIONS AUTHORIZATION
(note 3)
Signal f = 67KHz
Signal f = 114KHz
Signal f = 190KHz
Pilot Threshold Voltage
Pilot Threshold Voltage
Pilot Indicator Saturation
Voltage
Pilot Indicator Leakage Current
Control Voltage for forced mono
for stereo "ON"
for stereo "OFF"
I = 1mA
V = 9V
α
= < 3dB
12
7
75
95
84
20
14
0.2
28
21
0.5
10
0.8
dB
dB
dB
mV
RMS
mV
RMS
V
µA
V
ACI - ADJACENT CHANNEL INTERFERENCE
(note4)
α114
α190
V
INTH
V
INTH
V
PI
I
PI
V
19
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bs
f
mod
= 10KHz; f
spur
= 1KHz
f
mod
= 13KHz; f
spur
= 1KHz
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30
55
P
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4.5
45
0.02
91
100
0
70
75
62
90
65
75
70
10
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10.5
50
4.8
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Ω
V
dB
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dB
dB
0.3
%
dB
dB
4
mV
dB
dB
dB
dB
dB
dB
dB
Signal f = 57KHz
MONO/ STEREO SWITCH
3/12
TDA7338
Table 4.
(V
CC
= 9V; modulation frequency: 1KHz; de-emphasis time: T = 50µs; nominal MPX input voltage:
V
MPX
= 1.5V
PP
; m 100% (75KHz deviation, f
mod
= 1KHz); R
IN
= 40.2kΩ, R
OUT
= 40.2kΩ;
T
amb
= 27°C; C
REF
= 4.7µF; unless otherwise specified)
STEREO BLEND
V
16-17
V
16-17
Control Voltage for Channel
Separation
Control Voltage for Channel
Separation
De-Emphasis Time Constant
High Cut Control Resistance
High Cut Control Resistance
Oscillator Frequency
Capture and Holding Range
V
CO OFF
Trigger Threshold (note 6)
Pin 7
V
PEAK
= 1.3V; PROG = GND
V
PEAK
= 1.3V;
PROG = OPEN/V
DD
V
TR
Trigger Threshold
V
PEAK
= 1.5V;
PROG = OPEN/V
DD
T
S
I
OS
V
N1
V
N2
V
N3
Suppression Pulse Duration
Input Offset Current during
suppression time
V
PEAK
(pin 8)
V
PEAK
(pin 8)
V
PEAK
(pin 8)
α
= 6dB; V
R
= 3.6V (note 5)
α
= 26dB;
-0.31
-85
-0.27
-55
-0.23
-30
V
mV
HIGH CUT CONTROL
τ
deemp
R
15-17
R
15-17
VCO
f
osc
∆f/f
V
VCO
V
TR
with Murata CSB456F11
456
±1
C
13
, C
14
= 1nF; V
15-17
= 50mV
V
15 - 17
= 50mV
V
15 - 17
= -0.5V (note 5)
43
43
115
50
50
150
57
57
185
µs
KΩ
KΩ
NOISE INTERFACE DETECTOR
(test condition: V
SB
> V
R
+ 50mV)
V
PEAK
= 1.5V; PROG = GND
3.1 NOTES TO THE CHARACTERISTICS
1) INTERMODULATION SUPPRESSION
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C
BLANK
= 470pF
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180
250
260
340
50
10
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KHz
%
0.6
mV
mV
mV
mV
µs
pA
1.3
2
2.8
V
V
V
V
IN
= 0mV
RMS
V
IN
= 50mV
RMS
; f = 150KHz
V
IN
= 100mV
RMS
; f = 150KHz
0.7
1.1
1.7
1.0
1.5
2.3
V
O
(
signal
) (
at1KHz
)
-
α2
= -----------------------------------------------------------------
; f
s
= (2 x 10KHz) - 19KHz
V
O
(
spurious
) (
at1KHz
)
V
O
(
signal
) (
at1KHz
)
α3
= -----------------------------------------------------------------
; f
s
= (3 x 13KHz) - 38KHz
-
V
O
(
spurious
) (
at1KHz
)
measured with : 91% mono signal; 9% pilot signal; fm=10KHz or 13KHz
2) TRAFFIC RADIO (V.F.) suppression
V
O
(
signal
) (
at1KHz
)
α57 (
V.W.F.
)
= -------------------------------------------------------------------------------------------
-
V
O
(
spurious
) (
at1KHz
±
23KHz
)
measured with : 91% stereo signal; 9% pilot signal; fm=1KHz; 5% subcarrier
(f = 57KHz, fm = 23Hz AM, m = 60%)
4/12
TDA7338
3. SCA (SUBSIDIARY COMMUNICATIONS AUTHORIZATION)
V
O
(
signal
) (
at1KHz
)
-
α67
= -----------------------------------------------------------------
; f
s
= (2 x 38KHz) - 67KHz
V
O
(
spurious
) (
at9KHz
)
measured with : 81% mono signal; 9% pilot signal; fm=1KHz;
10% SCA - subcarrier (fs = 67KHz, unmodulated)
4. ACI (ADJACENT CHANNEL INTERFERENCE)
V
O
(
signal
) (
at1KHz
)
-
α114
= -----------------------------------------------------------------
V
O
(
spurious
) (
at4KHz
)
; f
s
= 110KHz - (3 x 38KHz)
V
O
(
signal
) (
at1KHz
)
α190
= -----------------------------------------------------------------
-
V
O
(
spurious
) (
at4KHz
)
; f
s
= 186KHz - (5 x 38KHz)
measured with : 90% mono signal; 9% pilot signal; fm=1KHz; 1% spurious signal
(fs = 110KHz or 186KHz, unmodulated)
5. Control range typ 11% of VR (see figure 5 and figure 6)
6. MEASUREMENT OF TRIGGER THRESHOLDS
All thresholds are measured by using a pulse with T
R
= 2µs, T
HIGH
= 2µs, and T
F
= 10µs. The repetition
rate must not increase the PEAK voltage.
Figure 4.
Vin
VTR
4
4.1 Signal Path
The TDA7338 Stereodecoder contains all necessary functions for processing the MPX signal. Due to the
external input resistance (Pin 20) the circuit can be adapted to different MPX input levels. Behind 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 resistor 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. = 50µs, see fig. 5). If the RF-signal is weak, the corner frequency is
reduced down to 1kHz to improve the signal to noise ratio.
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FUNCTIONAL DESCRIPTION
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TR
THIGH
TF
Time
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