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TDA7338
April 2005
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
■VERY HIGH SUPPRESSION OF HARMONIC
AND INTERFERENCE SIGNALS
2 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 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
STEREO DECODER
Figure 2. reached.Block Diagram
Rev. 9
Fi
gure 1.
P
ac
k
age
Table 1. Order Codes
Part Number Package
TDA7338D SO20
TDA7338D013TR SO20 in Tape & Reel
SO20
Obsolete Product(s) - Obsolete Product(s)
TDA7338
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Table 2. Absolute Maximum Ratings
Table 3. Thermal Data
Figure 3. Block Diagram and Test Circuit
Symbol Parameter Value Unit
V
CC
DC Supply Voltage 10.5 V
I
CC
Suply Current 20 mA
T
stg
Storage Temperature -55 to 150 °C
T
amb
Operating AmbientTemperature -40 to 85 °C
Symbol Parameter Value Unit
R
th j-pins
Thermal resistance junction-pins 200 °C/W
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
HCRHCL
MONO
PILOT
IND. VR VSB VHCC
MPX IN
CSB456F11
VCO
2617835
VCO OFF MUTE
TBLANK PEAK
LEVEL PROG GND VS
D95AU364C
20 19 18 17 16 15 14 13
12
11
10
9
4
1µF
40.2K
1nF 1nF
70K 40.2K
40.2K
4.7µF
47nF
470pF
Obsolete Product(s) - Obsolete Product(s)
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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 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) f
m
= 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 Ω
V
O
DC Output Voltage pin 10 and 11 4.2 4.5 4.8 V
αChannel Separation V
R
- V
SB
= -50mV
DC
30 45 dB
THD Total Harmonic Distortion 0.02 0.3 %
Signal plus noise to noise ratio f = 20Hz to 16KHz; S = 2Vrms 91 dB
α
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
α19 Pilot Signal f = 19KHz 55 70 dB
α38 Subcarrier f = 38KHz 75 dB
α57 Subcarrier f = 57KHz 62 dB
α76 Subcarrier f = 76KHz 90 dB
INTERMODULATION (note 1)
α2f
mod
= 10KHz; f
spur
= 1KHz 65 dB
α3f
mod
= 13KHz; f
spur
= 1KHz 75 dB
TRAFFIC RADIO (note 2)
α57 Signal f = 57KHz 70 dB
SCA - SUBSIDIARY COMMUNICATIONS AUTHORIZATION (note 3)
α67 Signal f = 67KHz 75 dB
ACI - ADJACENT CHANNEL INTERFERENCE (note4)
α114 Signal f = 114KHz 95 dB
α190 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 µA
V
19
Control Voltage for forced mono α = < 3dB 0.8 V
SN+
N
--------------
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TDA7338
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3.1 NOTES TO THE CHARACTERISTICS
1) INTERMODULATION SUPPRESSION
; f
s
= (2 x 10KHz) - 19KHz
; f
s
= (3 x 13KHz) - 38KHz
measured with : 91% mono signal; 9% pilot signal; fm=10KHz or 13KHz
2) TRAFFIC RADIO (V.F.) suppression
measured with : 91% stereo signal; 9% pilot signal; fm=1KHz; 5% subcarrier
(f = 57KHz, fm = 23Hz AM, m = 60%)
STEREO BLEND
V
16-17
Control Voltage for Channel
Separation
α = 6dB; V
R
= 3.6V (note 5) -0.31 -0.27 -0.23 V
V
16-17
Control Voltage for Channel
Separation
α = 26dB; -85 -55 -30 mV
HIGH CUT CONTROL
τ
deemp
De-Emphasis Time Constant C
13
, C
14
= 1nF; V
15-17
= 50mV435057 µs
R
15-17
High Cut Control Resistance V
15 - 17
= 50mV 435057KΩ
R
15-17
High Cut Control Resistance V
15 - 17
= -0.5V (note 5) 115 150 185 KΩ
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 µs
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
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)
α2VOsignal()at1KHz()
VOspurious()at1KHz()
------------------------------------------------------------------=
α3VOsignal()at1KHz()
VOspurious()at1KHz()
------------------------------------------------------------------=
α57 V.W.F.() VOsignal()at1KHz()
VOspurious()at1KHz 23KHz±()
--------------------------------------------------------------------------------------------=
Obsolete Product(s) - Obsolete Product(s)
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TDA7338
3. SCA (SUBSIDIARY COMMUNICATIONS AUTHORIZATION)
; f
s
= (2 x 38KHz) - 67KHz
measured with : 81% mono signal; 9% pilot signal; fm=1KHz;
10% SCA - subcarrier (fs = 67KHz, unmodulated)
4. ACI (ADJACENT CHANNEL INTERFERENCE)
; f
s
= 110KHz - (3 x 38KHz)
; 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.
4 FUNCTIONAL DESCRIPTION
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.
α67 VOsignal()at1KHz()
VOspurious()at9KHz()
------------------------------------------------------------------=
α114 VOsignal()at1KHz()
VOspurious()at4KHz()
------------------------------------------------------------------=
α190 VOsignal()at1KHz()
VOspurious()at4KHz()
------------------------------------------------------------------=
VTR
Vin
DC
TRTHIGH TF
Time
D95AU365
Obsolete Product(s) - Obsolete Product(s)
TDA7338
6/12
Figure 5. High Cut Control Figure 6. Stereo Blend
-0.5 -0.4 -0.3 -0.2 -0.1 0.0 VHCC-VR(V)
0
1
2
3.18
(=50µs)
fc
(KHz)
VR=3.6V
D95AU366
-0.40 -0.32 -0.24 -0.16 -0.08 VSB-VR(V)
0
10
20
30
40
50
SEP
(dB)
VR=3.6V
D95AU367
Furthermore the conditions of the stereo separation (see fig.6) can be controlled through the signal applied
to Pin 16 (VSB). Both signal levels (VSB and VHCC) are referred to Pin 17 (VR), with the characteristic
that the control range is 11% of VR. By modifying the feedback resistor value of the output stages (Pin 9
- 10, Pin 11 - 12) the total gain of the stereodecoder can be modified.
Pin 7 and Pin 8 have an additional function. By pulling them to ground the VCO-OFF (Pin 7) and the MUTE
(Pin 8) function are activated. The MUTE signal disconnects the MPX-signal from the circuit, while in com-
bination with VCO-OFF also the output buffers are disconnected from the circuit. In this mode the output
buffers can be used for AM-stereo, cassette play back and other purposes.
4.2 AM Mono Mode
By selecting VCO-OFF (Pin 7 to GND) the VCO is switched off and the SB and HCC are disabled. The
deemphasis time constant is changed to 40µs (f
c
= 4KHz).
4.3 DESCRIPTION OF THE NOISE BLANKER
In the normal automotive environment the MPX signal is disturbed by ignition spikes, motors and high fre-
quency switches etc.
The aim of the noise blanker part is to cancel the influence of the spikes produced by these components.
Therefore the output of the stereodecoder is switched off for a time of 40µs (average spike duration).
In a first stage the spikes must be detected but to avoid a wrong triggering on high frequency noise a com-
plex trigger control is implemented. Behind the trigger stage a pulse former generates the 40ms "blanking"
pulse. This duration of 40µs can be varied by changing the capacitor at pin 7.
4.3.1 Trigger Path
The incoming MPX signal is highpass-filtered, amplified and rectified (block RECT-PEAK). The second
order highpass-filter has a corner-frequency of 140KHz.
The rectifier signal, RECT, is used to generate by peak-rectification a signal called PEAK, which is avail-
able at the PEAK pin 8.
Also noise with a frequency >100KHz increases the PEAK voltage. The value of the PEAK voltage influ-
ences the trigger threshold voltage Vth (block ATC). The higher the noise level the higher the threshold.
Both signals, RECT and PEAK+Vth are fed to a comparator (block PEAK-COMP) which outputs a saw-
tooth-shaped waveform at the TBLANK pin 7. A second comparator (block BLANK-COMP) forms the in-
ternal blanking duration of 40µs. The noise blanker is supplied by his own biasing circuit (block BIAS-
MONO) to avoid any cross talk to the signal path (block BIAS-MONO).
Obsolete Product(s) - Obsolete Product(s)
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TDA7338
4.3.2 Noise Controlled Threshold Adjustment (ATC)
The behaviour of the noise controlled threshold adjustment is shown in fig. 8. It can be influenced lightly
by adding a resistor in parallel to the PEAK capacitor at Pin 8 either to GND or VDD. A resistor to GND
will decrease the threshold whereas a resistor to VDD will increase it. But it is recommended to choose
one of the internal thresholds by use of the PROG pin (see table 5)
4.3.3 Automatic Threshold Control by the Stereoblend voltage (ATC-SB)
Besides the noise controlled threshold adjustment there is an additional possibility for influencing the trig-
ger. It is controlled by the difference between Vsb and Vr, similar to the Stereoblend. The reason for im-
plementing such a second control will be explained in the following: The point where the MPX signal starts
to become noisy is fixed by the RF part. Therefore also the starting point of the normal noise controlled
trigger adjustment is fixed (fig.9). But in some cases the behaviour of the noiseblanker can be improved
by increasing the threshold even in a region of higher fieldstrength, for the MPX signal often shows distor-
tion in this range, which leads to an undesired triggering.
Because of the overlap of this range and the range of the stereo/mono transition it can be controlled by
Vsb and Vr. This threshold increase is programmable (see fig. 9).
4.3.4 Blend Mode
Another possibility to avoid a disturbing triggering on modulation is to use the spikes on the fieldstrength
signal (LEVEL pin). But in the range of higher fieldstrength the signal saturates and no more spike detec-
tion is possible. For this reason the TDA7338 offers the "BLEND MODE". When "BLEND MODE" is acti-
vated a smooth transition between the LEVEL- and the MPX-signal is used to detect the spikes either on
LEVEL or on MPX.
In the lower fieldstrength range mainly the LEVEL-signal is used whereas in the higher range mainly the
MPX is used.
This switching is controlled also by the normal Stereoblend signal to avoid additional pins. "BLEND MODE
OFF" is activated by connecting the LEVEL pin to GND (LEVEL must be also connected to GND if not
used).
Figure 7. Block Diagram of the Noise Blanker
80KHz LP SIGNAL PATH
ATC
AUTOMATIC
THRESHOLD
CONTROL
PEAK+VTH
RECT-PEAK
BUF PEAK
AMP
RECT
-
+
PEAK COMP REF.
BLANK COMP
ADDITIONAL THRESHOLD
CONTROL
(ATC-SB)
40µs
LEFT
RIGHT to OUTPUTS
MPX IN
VR
VSB
CPEAK
47nF
CBLANK
330pF
D95AU368
-
+
140KHz HP
120KHz HP
LEVEL 2V
7V
THRESHOLD L/H
ADDITIONAL THRESHOLD
CONTROL on/off
PROG
VS
-
+
BLEND
ON/OFF
0.1V
BLEND
CONTROL
Obsolete Product(s) - Obsolete Product(s)
TDA7338
8/12
Table 5. Programming of the Noiseblanker
Figure 8. Trigger Threshold vs. V
PEAK
Figure 9. Behaviour of the Field Strength Controlled Threshold Adiustment
PIN 1 (PROG) Trigger Threshold Peak Voltage Control By Fieldstrength
GND LOW ON
OPEN HIGH ON
V
DD
HIGH OFF
100mV
60mV
NOISE ADJUSTED
TRIG. THRESHOLD
MIN. TRIG. THRESHOLD
300mV
180mV
0.9V
VTH
1.5V VPEAK(V)
D95AU369
2.2V
TRIG. THRESHOLD
0.9V
VPEAK
E'
D95AU370
MONO STEREO
noisy signal good signal
ATC_SB OFF
(PROG=VS)
NOISE
≈3V
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TDA7338
Figure 10. Application Diagram
100K
68K
33K
470nF 10K
680pF
MONO
MPX
4)
VR 17
19
20
PILOT_IND 18
16
15
SIGNAL
STRENGTH
47K
47K
47K 1)
68K 1)
100K
100K
VCO_OFF
(FM ENABLE)
330pF
7
10K
10K
MUTE
47nF
8
2 4
456KHz
35
VS 9V
100nF10µF
1nF 2)
1nF 2)
13
14
12
11
IN R
OUT
9
10
IN L
OUT
47K
47K
56pF 3)
56pF 3)
6 LEVEL
(SIGNAL STRENGTH)
D95AU371A
TDA7338
1) has to be adapted to the signal strength
2) for deemphasis = 50µs
3) not absolutely necessary
4
)
roll off: to be ad
j
usted to the tuner
p
art
1
Obsolete Product(s) - Obsolete Product(s)
TDA7338
10/12
Figure 11. SO20 Mechanical Data & Package Dimensions
OUTLINE AND
MECHANICAL DATA
DIM.
mm inch
MIN. TYP. MAX. MIN. TYP. MAX.
A 2.35 2.65 0.093 0.104
A1 0.10 0.30 0.004 0.012
B 0.33 0.51 0.013 0.200
C 0.23 0.32 0.009 0.013
D (1) 12.60 13.00 0.496 0.512
E 7.40 7.60 0.291 0.299
e 1.27 0.050
H 10.0 10.65 0.394 0.419
h 0.25 0.75 0.010 0.030
L 0.40 1.27 0.016 0.050
k 0˚ (min.), 8˚ (max.)
ddd 0.10 0.004
(1) “D” dimension does not include mold flash, protusions or gate
burrs. Mold flash, protusions or gate burrs shall not exceed
0.15mm per side.
SO20
0016022 D
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TDA7338
5 REVISION HISTORY
Table 6. Revision History
Date Revision Description of Changes
October 2004 8 First Issue in EDOCS
April 2005 9 Changed the Style-cheet in compliance to the new “Corporate Technical
Pubblications Design Guide.
Deleted DIP20 Package
Obsolete Product(s) - Obsolete Product(s)
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences
of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted
by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject
to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not
authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.
The ST logo is a registered trademark of STMicroelectronics.
All other names are the property of their respective owners
© 2005 STMicroelectronics - All rights reserved
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TDA7338
Obsolete Product(s) - Obsolete Product(s)
