Stereo Multiplex Decoder

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Malcolm Webb
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1 Linear ntegrated Circuits Stereo Multiplex Decoder For FM' Stereo Multiplex Systems 6+ead quad-in-line plastic package H-706 FEATURES: Requires the use ofonly one low-inductance tuning coi! Automatic stereo switching Directly drives a stereo indicator lamp up to 00 ma ncludes driver for stereo-/amp indicator Operates trom a wide range of power supplies: 0 to 6 volts Requires only one adjustment tor alignment Switching trom monaural to stereo and stereo to monaural produces no audible thumps RCA-CA3090AO', a monolithic silicon integrated circuit, is a stereo multiplex decoder intended for FM multiplex systems. The CA3090AO is the successor to the CA30900; it ofters three major advantages over the CA30900 as folows:. Can directly drive a stereo indicator lamp with a current drain of up to 00 ma. 2. Stereo Defeat/Enable control-voltage specifications. 3. Capable of operation with lower distortion. This, stereo multiplex decoder requires only one lowinductance tuning coil (requiresonly one adjustment for complete alignment), provides automatic stereo switching, energizes a stereo indicator lamp, and operates from a wide range of voltage supplies. Figure shows the block diagram for the CA3090AO. The input signal from the detector is amplified by a lowdistortion preamplifier and simultaneously applied to' both the 9-kHz and 38-kHz synchronous detectors. A 76-kHz signal, generated by a local voltage-controlled oscillator (VCO), is counted down by two frequency dividers to a 38 khz signal and to two 9-kHz signals in phase quadrature. The 9-kHz pilot-tone supplied by the FM detector is compared to the locally generated 9-kHz signal in a synchronous detector. The resultant signal controls the voltage controlled oscillator (VCO) so that it produces an output,signal to phase-oc.k the stereo decoder with the pilot tone. A second synchronous detector compares the locally generated 9-kHz signal with the 9-kHz pilot tone. f the pilot tone exceeds an externally adjustable threshold voltage, a Schmitt trigger circuit is energized. The signal fram the Schmitt trigger lights the stereo indicator, enables the 38-kHz synchronous detector, and automatically switches the CA3090AO from monaural to stereo operation. The output signal from the 38-kHz detector and the composite signal from the preamplifier are applied to a Low distortion: under 0.5% Separate dc input permits stereo deteat or enable High signal output: directly drives audlo amplifiers Excellent SCA (storecast) rejection: 55 db typ. High audio channel separation: 40 db typ. matrixing circuit from which emerge the resultant left and right channel audio signals. These signals are applied to their respective left and right post amplifiers for amplification to a level sufficient to drive most audio amplifiers. The CA3090AO may be used without the stereo defeau enable function (see Fig. 6) if a control voltage for this function is not readily available. n this case, Terminal 4 should be grounded. The CA3090AO utilizes the 6-lead quad-in-line plastic package and operates over the ambient temperature range, of -40 C to +85 C. 'Formerly Developmenlal Type No, TA6262G, MAXMUM RATNGS, Absolute-Maximum Values at TA = 25 C: OG Supply Voltage 6 V Gurrent at Term ma nput Signal Voltage (Gomposite) mv Ambient Temperature Range: Operating to +85 G Storage -65 to +50" G Lead Temperature (during soldering): At distanee not less than /32" (0,79 mm) trom ease tor 0 s max +265 G r-or stereo operation, a minimum input signal voltage (composite) of 40 mv is required. 860.

2 ELECTRCAL CHARACTERSTCS TV/CATV Circuits TEST CONDTONS TERMNAL Typ. T A =25 C Cir- MEASURED Char. V+ = 2 V (unless cuit CHARACTERSTC AND Curve specified otherwisel Fig. SYMBOL Fig. No. No. Static Characteristics. LMTS Min. Typ. Max. UNTS Total Current (Terms. 9, 0, ) total Lamp OFF ma DC Voltage: Term. V l V Term. 6!lndieator Lamp OFF) V V Terms. 9 and 0 V 9 & V Term. 2!lndieator Lamp OFF) V 2 V+ = 6 V V Voltage Differential (Term. 2-Term. ) V 2 -V l V Current at Term. 2 (n sctual use external circuit resistanee (e.g. lamp should limit Term. 2 to the 4 V N (at = 9 khz) = 8 mv ma maximum rated value 0 00 ma.l Dynamic Characteristics nput mpedanee ZN 7-50k - n Channel Separation (L + R Relerenee)* db Channel Balance (Monaural) db Monaural Gain V N = 80 mv db Stereo/Monaural Gain Ratio* 7 - ±o.3 ±3 db ndieator Lamp - Turn-ON Voltage 5 9-kHz pilot-tone@term mv Capture Range (Deviat!on fram 76-kHz center 9-kHz pilot-tone requeney) 7,8 voltage = 8 mv 7 :!S.6 ±0 - % Distortion (75'/ls de-emphasis): 2nd Harmonie V N = 240 mv % 3rd, 4th. and 5th Harmonie 7 - <0. - % 9-kHz Rejeetion dr 38-kHz Rejeetion db SCA (storecast) Rejeetion db Stereo Deleat Voltage V4) - <0.9 V Stereo Enable Voltage (V4) >.6 - V NOTE: For improved pilot sensitivity and overload characteristics. replaee the.039 F capacitor * For stereo operation, test eonditions require a eomposite between Terminals 7 and 8 with aseries L-C Network (L = 4.7 mh. C = 0.05/lF). Under these eonditions. ndieator Lamp Sensitlvity: 'ON' = 3.3 mv, 'OFF' = 2.0 mv stereo input signal (modulated"at khz) including a 9 khz (8 mv) pilot-tone signal. "o t---, len RGHT lai CQMPQSTE SGNAL 8 STEREO ENABLE SGNAL lei STEREO GATNG SGNAL {OJ DFFERENCE SGNAL L -'2v.00,A l AMP (.(2 PROVDE PARTAL DE-EMPHASS STEREODEFEAT ENAalE Fig. - RES,STANCE VALUES ARE," OHMS Funetianal block diagram af the CA3090AO. 86

3 Linear ntegrated Circuits A B c o E F e- r ,r , R57 R5a R62 R63 lok lok lok lok : -- ol "06 PLOT PRESENCE 6 FLTER! r ,.\42 y' 04 -, 09 3K,n 03 2 R59.60 R64 R65 2 [D20 R K 4K Dl K 24K,. 30K o R45A 4 70 o 3.6K :=t: 74 J.J 075'- B 0;; R66 2K 072 3K 2" k R46 R6a R6, R 38kHz TO '. 50K 3K 76kHz TO 7AY Da 38 khz 9 khz DVDER 00 ' DVDER 09, Oll J L J.J, l R43 ;;,44 R49 l R36 i _...J K 4K 6 02a 9K -A3 04 K4a, 05 R '" ;l:. 049 R39 30K SCHMTT TRGGER,LAMP DRVER CONTROL.8 A CR CONTROL K St; a : AoJUST G...J '-- r;: ,, , L-+- M ----;-< N 0 P Q L R329 5K r -{04A... 04a R50 R5 5K 5K RGHT CHANHEL 0 9 LEFT CHANNEL 34.lt035.4: R33 R56 R K 3.a6K R53 R32 R34 R52 R54 R55 K K.3K.3K.4K.4K i PLOT NEC;:T -l B OM'P...J 0--SENTTY--- 8 rt RESSTANCE YALUES ARE N OHMS Fig. 2 - Schematic diagram of the (cont'd from previous page); 36 92Cl-22497

4 TV/CATV Circuits r a TO OSC. { TUNNG CRCUT TO PHASE-LOCK LOOP FLTER 4 LAMP DRVER, NOTE THE BYPASS CAPACTOR MAY-BE OMTTEO WTH AN APPROXMATE LOSS OF ONLY db N GAN -c NOTE 2 F TERMNAL 3 S FLOATNG OR GROUNOED, THE CRCUT WLL FUNCTON N STEREO REGARDLESS OF THE VOLTAGE ON TERMNAL 4. F TERMNAL 3 S CONNECTED TOTERMNAL 6THROUGH A 47,000 OHMS RESSTORl, THE CRCUT CAN THEN DEFEAT OR ENABLE THE STEREO FUNCTON 5 -po '-' r-----l ;A l U l!:.a-.j r , R4 5K 'D4 42A 05 l L f'l 46 "02 '! ') R5 R22 R23 K 6K 6K 045 V R3 R6 R24 R70 R69 O.4K.8K K 40 r i :: :, i, i oth R3 r ;{03A.9K : NPUT Q5 R2 }---R----r '( : 50K -'079 0!50K,...06 R2 7K 07 R9 R7 R8 RO R2 : 3QK K K 30K 6K,g2 pf 0;; L!AL.!!!A!:!!!:.R...J NPUT NOTE 2 CRCUT BYPASS R20.8K R2 2K R8 5K Fig. 2 - Schemetic diagram of the (cont'd on next page). _K r , r--,25 R9 R2:JR26 ','.3K 6.7K.3K r---"" 5.4K Ol(,,08,--_... L Ol : i 0" ', M N.-!----::j---i-_-...,j-----;. 0 00,4:0 R29.K R28 R30 K K EE! JASEC!.!,Ec.!?_J 3 NOTE 2 4 OEF{T'WABLE S;;D 863

5 Linear ntegrated Circuits V4 >.6v TO ACTVATE STEREO V4< 0_9 v TO DEACTVATE STEREO Fig. 3-92C Test circuit for oe characteristics. Fig. 5-92C Test circuit tor use with stereo defeat/enab/e. CA309QAQ u 50 t -L H dl' r'! fh t- 25 :3 92C COLLECTQR-TO-EMTTER VOLTAGE (VCE-V Fig. 4 - ndicator lamp characteristics (/C VS. VCE)' 92C Fig. 6 - Test circuit for use without stereo defeat/enable. 390n v+ 0kn LEFT STERO GENERATOR O--+--'\N\r t-----H- NPUT 22k 0.00 p.f L RGHT TEST NETWORK. TO SMULATE db ROLLOFF AT 38 khz DUE TO FM OETECTOR RESSTANCE VAL.UES ARE N OHMS 92CM Fig. 7 - Test circuit for measurement of dynamic characteristics. 864

6 TV/CATV Circuits > E 30 -fc ;, "CAPTURE AREA" :.::: ;-;:-: oe POWER SUPPLY VOLTAGE l:=i:f::--:[:l\ (V +), 2v 25 ::::: LOOP FLTER CAPAC.'0.47F -' _ (TERM.4) _ AMSENT TEMPERATURE (TA) 20 :,\ '25"C fes::)..... Ü u ẓ.!:.6.. ụ. u... '".....J.: VOLTAGE-CQNTROLLED OSCLLATOR (VCO) FREQUENCY (NO PLOT TONE APPLlED)-kHz 92CS-9056 Fig. 8 - Pilot-tone voltage level vs. VCO frequency with no pilot-tone applied. M n VOLTAGE-CONTROLLED OSCLLATOR (VCO FREQUENCY (NO PLOT TONE APPLlED)-kHz 92CS-9055 Fig. 9 - Filter capacitance vs. VCO frequency with no pilot-tone applied. Fig. 0 - A-Foil side. 8-Componenr side. Photographs of the and outboard componenrs mounted on a 2 X 2).-inch printed-<:ircuit board to constitute a campere stereo multiolex decoder. 865

AM radio / FM IF stereo system IC

AM radio / FM IF stereo system IC The is an AM radio and FM IF stereo system IC developed for radio cassette players. The FM circuit is comprised of a differential IF amplifier, a double-balance type quadrature