I
MC13020P
I
Advance Information
MOTOROU
MOTOROM C-QUAM@
AM STEREO .t$;i:t,
DECODER ~’~i:: ‘“
*$1,
$,,,‘“::>
C-QUAM@ AM STEREO DECODER
This circuit is a complete one-chip full-feature AM stereo decoding and pilot detection system. It employs full-wave envelope
signal detection at all times for the L + R signal, and decodes
L– R signals only in the presence of valid stereo transmission.
.
No Adjustments,
SILICON MO~~~&&”b
lNTEGRATEO’~@lT
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No Coils
●
Few Peripheral Components
●
True Full-Wave Envelope Detection for L+ R
●
PLL Detection For L–R
. 25 Hz Pilot Presence Required To Receive L– R
●
I
Pilot Acquisition Time 300 ms For Strong Signels, Time
EMended For Noise Conditions To Prevent “Falsing”
. Internal Level Detector Can Be Used As AGC Source
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11
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PLASTIC PACKAGE
CASE 738-02
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\
3
a
“%
0.0033
Q Detector .20
Phase
Detector
Osc. Feedback
‘F’nput
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v
”,!”,
Tuner
AGC
,.
,.
11
TT I‘ 6Vcc
~i$ ‘l!
L,,>
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5 Error
Amplifier
Ground
.
==
u
Stereo Lamp
Pilot Detector
Input
;3
‘6
10:O1*
15
=
+
14
8
Right Output
1
0.47
Pilot Filter 13
Input
4.7 k
+
glo
0.47
Auto Monaural
56 k
~b
9 Forced
Co-channel 12
Input
l.sk
,OPFF
Monaural
10
2.2
MF
1:
=
Lock
+
-
T
=
x
I ::.?.- I ;;;;a:or
0.0033
220
k
Left Output
100k
.
a
’430
‘7
.~~+’
7
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Detector
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c
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Osc. Input
47 KF
19
*
~:;
AGC’d Q 11
output ~
430
4.7 pF >
*muRata Ceramic Resonator — CSA3.60MT7
and Temp. Comp. Capacitor — CSC500K7
.
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:
The purchase of the Motorola C-QUAM@ AM Stereo Decoder does not carry with such purchase any license by implication, estoppel or othewise,
under any patent rights of Motorola or others covering any combination of this decoder with other aiementa including use in a radio receiver. Upon
application by an interested Paw,
licenses are available from Motorola on its patants applicable to AM Stereo radio receivers.
Iis documsntcontains information on a new produti. Specificationsand information herein
B subject
to changa without
@MOTOROLA
notica.
.-
INC., 19S5
C-QUAM is a trademark of Motorola Inc.
ADI-725R2
—
“
MAXIMUM RATINGS
Symbol
Rating
Vcc
Supply Voltage
Pilot Lamp Current, Pin 15
Value
Unit
14
Vdc
50
mAdc
TA
-40 to +85
“c
Storage Temperature
T~tq
-65 to + 150
“c
Junction Temperature
TJ{max)
150
‘c
Powar Dissipation
Derate above 25°C
pD
1.25
10
w
mWPC
Operating Temperature
D
*,\
*’X,l,
$J,$<,.
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‘!i.,,:1+ts.,
,:?:L*S
,*,Y
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.?., <>.>:.
.. .:+\ <+
.t::.,,f
,1:
,}~~..
>:>’.’
~{,,.\
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..}\’~:*\,
I:it:p’.,.t
(Unmodulated,&~~ri*;~ircuit
Of
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1
Unit
TYP .s. ~‘i’’$,y~ax
ELECTRICALCHARACTERISTICS (VCC = 8.0 Vdc, TA = 25°C, Input Signal = 200 mVRMS
Figure 1 Unless Othemise
Noted.)
Min
Charaderistic
Power Supply Operating
—
Range
20
Supply Line Current Drain, Pin 6
Input Signal Level, Unmodulated,
6,0,]~@&jb
afv’’3@~,, b“”
,,, “~a
Pin 3, for Full Operation
Audio Output Level, 5070 Modulation,
Audio Output Level, 50% Modulation,
L only or R only
100
,,* :z:ti
16,q
‘k:<?
..?&i.,*
Monaural
Monaural
Stereo
s ‘“p
,$~~
:,.?~:*’\
~?>{,. ;$
~,*.
—
Channel Separation, L only or R only, 50% Modulation
*.1.
~ ‘“s~,,
Pilot Acquisition Time, VCO locked, after relaase of forced monaura~.,?~,
ti+
—
.x‘~.:
20
$2,%$,,RA4fl
Input Impedanca
—
‘$>’“’~
.~~t)~
~.ti.:::!*
~ n
‘~
\..:t~t:.
—
Output Impedance
.s ‘
:,*
\,~~
)
O signal
1.4
Level Detactor Filter Voltage, Pin 4,
‘1+’.’~:
,,
—
t$~ObiNVRMS Signal
....).. .<?.,
‘!’~..\..*,,,!>}:3:3
—
.$><$,.i~,,
In Lock
Lock Detector Filter Voltage, Pin 10
\ ,<*,
—
Out of Lock
.. !$$,,...,.
, ,, ~,-.
Output THD, 5070 Modulation
Force to Monaural,
Force to Monaural,
—
40
mAdc
357
mVRMS
220
280
mVRMS
110
140
mVRMS
0.5
1.0
—
—
“/0
30
—
dB
300
—
ms
27
6.0
—
—
k~
pF
100
150
Q
1.7
2.5
2.0
—
Vdc
7.8
0.8
—
—
Vdc
Vdc
PA
Pin 9, Pull Down for ~#@F~Mode
‘.th,
\
$:.*
>.$.,+\\
,.~..!
2.0
—
2.5
—
0.15
1.0
Pin 9, Pull Up.tw’~k,~~katic
—
—
‘3,5
<0.001
3.7
1.0
Mode
Vdc
B
Vdc
@
FIGURE 3 — MOTOROLA C-QUAM@
(I+ L+ R)cosO
-——
e
1
l+L+i
I
Avg.
Carrier
I
I
(L- R)coso
Envelope is
compatible
with existing
monaural
receivers.
B
M070ROkA
@
Semiconductor Products Inc.
“ ,,,
/
FIGURE 4 — BLOCK DIAGRAM
,.
Vcc
=
6A
2, ,
1, ,
“5* ,
+
+
)
4, , 10, ,
20, .
Optional
AGC
To Tuner
l+L+R
Env
DET
l/cose
0.01
+e
+
r
3
“
IF
Input
7
Var
Gain
4r
Phase
DET
9W
,
1e
———
r
——-
Vco
Monaural
___
A
I
Note 1: Output polarity
is
dsfined for recsiver front
See Text
end with L.O. abovs signal
frequency.
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MOTORO~ C-QUAM@ — COMPATIB~~$“1,,
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QUADRATURE AM STEREO
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INTRODUCTION
“::t~i:t~
.\\+
In C-QUAM@, conventional,, ~~~d$ture
amplitude
modulation has been modifie~,~y ~dftipiying each axis
by COSOas ‘shown in ~g~~j~sdfid
3. The resulting
carrier envelope is 1 + L.,+~+,i~~., a correct sum signal
for monaural receiver&a*
”’Forstereo receivers opersting in monaural mod@$y# 25 Hz pilot signal is added
to the L-R infor~~,~’n,at
a 4% modulation level.
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THE DECOQ,~, ::$
The M~~$*
takes the output of the AM IF amplifier
and p~~as
the complete C-QUAM@ decoding functio~r+~~~,?absence of a good stereo signal, it produces
a@J&,Wgraded monaural output. Note in Figure 4 that
$~$~~+ R information delivered to the output always
‘&mes from the envelope detector (Env DET).
The MC1 3020P decodes the stereo information by
first converting the C-QUAM@ signal to QUAM, and then
. detecting QUAM. The conversion is accomplished by
comparing the output of the Env DET and the I DET in
the Err AMP. This provides the l/cos8 correction factor,
which is then multiplied by the C-QUAM@ incoming signal in the Var Gain block. Thus, the output of the Var
Gain block is a QUAM signal, which can then be syn-
chronously detected by conventional means; The I and
Q detectors are held at 0° and 90° relative demodulation
angles by reference signals from the phase-locked,
divided-down VCO. The output of the I DET is 1 + L+ R,
with the added benefit (over the Env DET) of being able
to produce a negative output on strong co-channel or
noise intetierence. This is used to tell the Lock circuit
to go to monaural operation. The output of the Q DET
is the L– R and pilot information.
THE VCO
The VCO operates at 8 times the IF input frequency,
which ensures that it is out-of-band, even when a 260
kHz IF frequency is used. Typically a 450 kHz IF frequency is used with synthesized front ends. This places
the VCO at 3.6 MHz, which permits economic crystal
and ceramic resonators. A crystal VCO is very stable,
but cannot be pulled very far to follow front-end mistuning. Pull-in capability of * 100 Hz at 450 kHz is typical,
and de-Q-ing with a resistor (see Figure 7) can increase
the range only slightly. Therefore, the crystal approach
can only be used with very accurate, stable front-ends,
By comparison, ceramic and L– C VCO circuits offer
pull-in range in the order of *2,5 kHz (at 450 kHz), Ceramic devices accurate enough to avoid trimming adjustment can be obtained with a matched capacitor for
Cs (see Figures 1 and 5).
~
0
MOTOROLA
@
Semiconductor Products /nc.
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In the PLL filter circuit on Pin 19, Cl is the primary
factor in setting a loop corner frequency of 8-10 Hz, inIock. An internally controlled fast pull-in is provided, R2
is selected to slightly overdamp the control loop, and
C2 prevents high frequency instability,
The Level DET block senses carrier level and provides
an optional tuner AGC source, It also operates on the
Q AGC block to provide a constant amplitude of 25 Hz
pilot at Pin 11, and it delivers information to the pilot
decoder regarding signal strength.
!
below the preset threshold. Seven consecutive co;%ts
S
of no pilot will also put the decoder in monaural. [h
stereo, the co-channel input is disabled, and co-channel -or other noise is detected by negative excursions of the
I DET, as mentioned earlier. When these excursions
reach a level caused by approximately 2070 modulati
of co-channel, the lock detector puts the system in mo*
aural, even though the PLL may still actually be locked.
This higher level of co-channel tolerance provides the
hysteresis to prevent chattering in and out of stereo on
S.)*
a marginal signal.
When all inputs to the Pilot Decode block$~aisorrect,
and it has completed its count, it turn~fo~j$~
Switch,
sending the L– R to the Matrix, and $@Q#$s the pilot
lamp pin to a low impedance to,~~~.~>
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‘~:
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SUMMARY
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PILOT AND CO-CHANNEL FILTERS
The Q AGC output drives a low pass ‘filter, made up
of 4000
internal, and 430 Q and 5 KF external, From
this point, an active 25 Hz band-pass filter is coupled to
the Pilot Decoder, Pin 14, and another low-pass filter is
connected to the Co-channel Input, Pin 12. A 2:1 reduction of 25 Hz pilot level to the Pilot Decode circuit
It should be noted that i#~:@UAM@, with both chanwill cause the system to go monaural, with the comnels AM modulated, ~~,&~$oi4& increase in stereo is a
ponents shown. Refer to Figure 8 for the formulas govmaximum of 3.0 d~R+:&n
program material. Thereerning the active band-pass filter, The co-channel input
fore, this is not th#”’’pa~dFconcern in the choice of monsignal contains any low frequency intercarrier beat
aural to stereo sk~~@%g point as it was in FM, and blend
~J:\>\’4...’~@,>.
notes, and, at the selected level, prevents the Pilot Deis not needed>~;;;~
code circuit from going into stereo. The co-channel in~~s>::~,
:,?,
.$”+3,
.,~f~:e
put, Pin 12, gain can be adjusted by changing the ex.1>.?:
,<,,
\.~~’~,’:..
~>.
ternal 1.5 k resistor. The values shown set the “trip”
y., $;
;,*.
‘~:,“*::.:>*,,!? PIN DESCRIPTIONS
level at about 7% modulation. The 25 Hz pilot signal at
~~:;~j:,2”_ Detector Filters, Rout = 4.3 k, recommend
the output of the active filter is opposite in phase to the
.$)
$,1,., 0.0033 pF to VCC to filter 450 kHz compo:,,.
,.
pilot signal coming from the second low-~ass filter. The
,,)<.,
nents.
56 k resistor from-Pin 14 to Pin 12 causes the pilot to
.,$: i-h..
be cancel led at the co-channel input. This allows-a more ;*...,*,>
$“”’’’f$Pin
3
—
IF
Signal Input
\.$~
.<!.
,, ‘$’ Pin 4
— Level Detector filter pin, Rout = 8,2 k, 10 ~F
sensitive setting of the co-channel trip level,
,.,.>:<
\.\,,
\:.>ac,
ZIJ,
..~~.
.....
to ground sets the AGC time constant. High
‘tc,~,,
impedance output, needs buffer.
THE PILOT DECODER
*:$’
— Error Amp compensation to stabilize the Va
The Pilot Decoder has two modes of operat[@~ Wtien
Pin 5
#
Gain feedback loop
signal conditions are good, the decoder wil~.sm$h to
— Vcc, 6-10 Vdc, suitable for low Vbati autoPin 6
stereo after 7 consecutive cycles of the 2,5 %~ibt tone.
motive operation, but must be protected
When signal conditions are bad, the,$~~~t,~
intetierence changes the pilot counter so as~qj~wlre
37 confrom “high line” condition.
secutive cycles of pilot to go to ~$w~~n
a frequency
Pin 7,8 — Left and Right Outputs, NPN emitter followers
synthesized radio, the logic .tha%,m~&%the audio when
Pin 9
— Forced Monaural, MOS or TTL controllable
tuning can be connected to.~ ‘*!When this pin is held
low it-holds the decoder i~<~j~~q~rai mode and switches
Pin 10 — Lock detector filter, ‘Rout = 27 k, recomit to the short count. T@p@
should be held low until
mend 2.2 pF to ground.
Pinll
— AGCd Q output, NPN emitter follower with
the synthesizer andj.~-r
have both locked onto a
400 Q from emitter to Pin 11
new station. A 3~9 *+.&$&lay should be sufficient. If the
Pin 12 — Co-channel Input, 2.0 k series in and 47 k
synthesizer log;@,@es’’not provide sufficient delay, the
feedback
circuit show~~~fi~$$i~ure 9 may be added. Once Pin 9
goes high,$$~m-,~jiot Decoder starts counting. If no pilot
Pin 13 — Pilot Filter Input to op amp, see Figure 8
is detect~~~
seven consecutive counts, it is assumed
Pin 14 — Pilot Decode Input (OP amp output) emitter
follower, Rout = 100 Q
to b,~,$’~,+qdbd monaural station and. the decoder is
Pin 15 — Stereo Lamp, open-collector
of an NPN
swiah~
10 the long count. This reduces the possibility
.p~$~~stereo
triggering due to signal level fluctuation
common emitter stage, can sink 50 mA,
.$:i.i
.i)i.c.f,...-,,.,
Vsat = 0.3 V at 5.0 mA
~,wianolse. If the PLL goes out of lock, or interference is
Pin 16 — Ground
‘$;;*tected
by the co-channel protection circuit before
Pin 17 — Oscillator input, Rin = 10 k, do not dc con‘$:seven cycles are counted, the decoder goes into the long
count mode. Each disturbance will reset the counter to
nect to Pin 18 or ground
zero. The Level Detector will keep the decoder from
Pin 18 — Oscillator feedback, NPN emitter, Rout =
100a
going into stereo if the IF input level drops 10 dB, but
will not change the operation of the pilot counter.
Pin 19 — Phase Detector Output, current source to filOnce the decoder has gone into the stereo mode, it
ter
will go instantly back to monaural if either the lock dePin 20 — Detector Filter, Rout = 4.3 k, recommend
tector on Pin 10 goes low, or if the carrier level drops
0,0033 pF to VCC to filter 45o kHz
4
m
MOrOROkA
Semiconductor Products Inc.
*-
0
FIGURE 5 — CERAMIC VCO
20
~
4.5 --%
FIGURE 6 — L – C VCO
,
5.0
19
:;?
1
lE
I
I
I
17
mu Rata
CSA3.60M~
,4
b
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FIGURE 7 — CRYSTAL VCO
.~@@;E
8 – ACTIVE BAND-PASS
FILTER
0
vr~f
3,5
>
Q
Rc=~
Rc
Ra=~
Ra Rc
‘b
‘4QZRa–
Rc
where, in this application:
f. = center frequency = 25 Hz
A. = gain at fo<25
Q<1O
Choose values for fo, Ao, Q, and
convenient C, solve for
resiatora
0.47 PF
4.7 k
910
220 k
0.33 PF
8.2 k
1.3 k
330 k
Note: Capacitor C should be a good grsda, low ESR.
0
M070ROLA
@
Semiconductor Products Inc.
OUTLINE DIMENSIONS
Motorola reservee the right to make changes without further notice to any products herein to improve reliability, function or design. Motorola does
not assume any Iiabilityarising
out of the application or use of any product or circuit described herein: neither doea lt convey any license under its
patent rights nor the rights of others. Motorola and @are registered trademarks of Motorola. Inc. Motorola, Inc. is an Equal Employment Opportunity/
Affirmative Action Employer.
MOTOROLA
@
Semiconductor Products Inc.
BOX 20912.
●
PHOENIX,
ARIZONA
85036
●
A SUBSIDIARY
OF MOTOROLA
INC.
—