MC13020P Ver la hoja de datos (PDF) - Motorola => Freescale
Número de pieza
componentes Descripción
Fabricante
MC13020P Datasheet PDF : 6 Pages
| |||
In the PLL filter circuit on Pin 19, Cl is the primary
,!
!
below the preset threshold. Seven consecutive co;%ts S
factor in setting a loop corner frequency of 8-10 Hz, in-
of no pilot will also put the decoder in monaural. [h
Iock. An internally controlled fast pull-in is provided, R2
stereo, the co-channel input is disabled, and co-channel --
is selected to slightly overdamp the control loop, and
or other noise is detected by negative excursions of the
C2 prevents high frequency instability,
I DET, as mentioned earlier. When these excursions
The Level DET block senses carrier level and provides
reach a level caused by approximately 2070 modulati
an optional tuner AGC source, It also operates on the
Q AGC block to provide a constant amplitude of 25 Hz
of co-channel, the lock detector puts the system in mo*
aural, even though the PLL may still actually be locked.
pilot at Pin 11, and it delivers information to the pilot
This higher level of co-channel tolerance provides the
decoder regarding signal strength.
hysteresis to prevent chattering in and out of stereo on
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 re-
duction of 25 Hz pilot level to the Pilot Decode circuit
will cause the system to go monaural, with the com-
ponents shown. Refer to Figure 8 for the formulas gov-
erning the active band-pass filter, The co-channel input
signal contains any low frequency intercarrier beat
notes, and, at the selected level, prevents the Pilot De-
code circuit from going into stereo. The co-channel in-
put, Pin 12, gain can be adjusted by changing the ex-
ternal 1.5 k resistor. The values shown set the “trip”
level at about 7% modulation. The 25 Hz pilot signal at
the output of the active filter is opposite in phase to the
pilot signal coming from the second low-~ass filter. The
56 k resistor from-Pin 14 to Pin 12 causes the pilot to
a marginal signal.
S.)*
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
lamp pin to a low impedance to,~~~.~>
SUMMARY
,,:$...,>:.,~\+v..,,\+.<,,.’,‘!~.,:j.,a$:.:<:,h?3,~‘~/}:~,‘~~:c’
the pilot
It should be noted that i#~:@UAM@, with both chan-
nels AM modulated, ~~,&~$oi4& increase in stereo is a
maximum of 3.0 d~R+:&n program material. There-
fore, this is not th#”’’pa~dFconcern in the choice of mon-
aural to stereo~sJk:\~>~\’@4..%.’~g@p,>o.int as it was in FM, and blend
is not needed>~;;;~
.$.~1”.~>+,:~s.3,??f>,~:,:::e~,
‘~:“y,.,<,*\.:,~,:.~:$>;’~,;**,,~.’,:!>.?.. PIN DESCRIPTIONS
~~:;~j:,2”_ Detector Filters, Rout = 4.3 k, recommend
,,):<.,$,...,) $,1,., 0.0033 pF to VCC to filter 450 kHz compo-
.,$: i-h..
nents.
be cancel led at the co-channel input. This allows-a more ;*.$..“,*”,>’’\’.f$$~Pin 3
sensitive setting of the co-channel trip level,
,.Z,.I>J.\..:.<,~\<.\,.,!:~,.,...>‘.$a’c, Pin 4
‘tc,~,,
THE PILOT DECODER
*:$’
— IF Signal Input
— Level Detector filter pin, Rout = 8,2 k, 10 ~F
to ground sets the AGC time constant. High
impedance output, needs buffer.
The Pilot Decoder has two modes of operat[@~ Wtien
signal conditions are good, the decoder wil~.sm$h to
Pin 5 — Error Amp compensation to stabilize the Va #
Gain feedback loop
stereo after 7 consecutive cycles of the 2,5%~ibt tone.
Pin 6 — Vcc, 6-10 Vdc, suitable for low Vbati auto-
When signal conditions are bad, the,$~~~t,~ intetier-
motive operation, but must be protected
ence changes the pilot counter so as~qj~wlre 37 con-
from “high line” condition.
secutive cycles of pilot to go to ~$w~~n a frequency
Pin 7,8 — Left and Right Outputs, NPN emitter follow-
synthesized radio, the logic .tha%,m~&%the audio when
ers
tuning can be connected to.~ ‘*!When this pin is held
Pin 9 — Forced Monaural, MOS or TTL controllable
low it-holds the decoder i~<~j~~q~rai mode and switches
Pin 10 — Lock detector filter, ‘Rout = 27 k, recom-
it to the short count. T@p@ should be held low until
mend 2.2 pF to ground.
the synthesizer andj.~-r
have both locked onto a
Pinll — AGCd Q output, NPN emitter follower with
new station. A 3~9 *+.&$&lay should be sufficient. If the
400 Q from emitter to Pin 11
synthesizer log;@,@es’’not provide sufficient delay, the
Pin 12 — Co-channel Input, 2.0 k series in and 47 k
circuit show~~~fi~$$i~ure 9 may be added. Once Pin 9
feedback
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
to b,~,$’~,+qdbd monaural station and. the decoder is
follower, Rout = 100 Q
swiah~ 10 the long count. This reduces the possibility
Pin 15 — Stereo Lamp, open-collector of an NPN
.$.p:i~.i$)i~.c~.sf,t.e..r-e,,o., triggering due to signal level fluctuation
~,wianolse. If the PLL goes out of lock, or interference is
common emitter stage, can sink 50 mA,
Vsat = 0.3 V at 5.0 mA
‘$;;*tected by the co-channel protection circuit before
Pin 16 — Ground
‘$:seven cycles are counted, the decoder goes into the long
Pin 17 — Oscillator input, Rin = 10 k, do not dc con-
count mode. Each disturbance will reset the counter to
nect to Pin 18 or ground
zero. The Level Detector will keep the decoder from
going into stereo if the IF input level drops 10 dB, but
Pin 18 — Oscillator feedback, NPN emitter, Rout =
100a
will not change the operation of the pilot counter.
Pin 19 — Phase Detector Output, current source to fil-
Once the decoder has gone into the stereo mode, it
ter
will go instantly back to monaural if either the lock de-
Pin 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.
Share Link: 