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PHASE LOCKED LOOP APPLICATIONSTRANSIENT PHASE ERROR AS ANINDICATION OF DAMPING0.7 6W .----r---,-----r----,----,.---,--r------,wn0.6 I----F---=-=~--+---+---+---+--I-----I0.5 I--~~~+_\_-+---+---+---+--I-----I0.40.30.2NOISE EFFECTSThe effect of input noise on loop operation is very difficultto predict. Briefly, the input noise components near thecenter frequency are converted to phase noise. When thephase noise becomes so great that the ±90 0 permissiblephase variation is exceeded, the loop drops out of lock orfails to acquire lock. The best technique is to actually applythe anticipated noise amplitude and bandwidth to theinput and then perform the capture and lock rangemeasurements as well as perform operating tests with theanticipaterl input lel(:~1 J;,d modulation deviations. Byincluding a small safety factor in the loop design tocompensate for small processing variations, satisfactoryoperation can be assured.DAMPING-0.1 I--_FA+-C_TO_R--+_----1r--~+--- «==-++-_--+_~-0.2 I---+---+---+--~ __ -+~__+--I__---I-0.3 1.--_.1..-_....1...-_--1-_--'-_---'-_---' __ 1-----.1Figure 8-18Another way of estimating damping is to make use of thefrequency response plot measured fo~ the natural frequency(w n ) measurement. For low damping constants, thefrequency response measurement peak will be a strongfunction of damping. For high damping constants, the3dB-down point will give the damping. Table 8-3 givesthe approximate relationship.SIMPLIFIED MEASUREMENT EQUIPMENTThe majority of the PLL tests described can be done witha signal generator, a scope and a frequency counter. Mostlaboratories have these. A low-cost digital voltmeter willfacilitate accurate measurement of the VCO conversiongain. Where the need for a FM generator arises, it may bemet in most cases by the VCO of a Signetics PLL. (Seethe applications in this <strong>section</strong>.) Any of the loops may beset up to operate as a VCO by simply applying themodulating voltage to the low pass filter terminal(s). Theresulting generator may be checked for linearity by usingthe counter to check frequency as a function of modulatingvoltage. Since the VCOs may be modulated right down todc, the calibration may be done in steps. Moreover,Gardner *' shows how loop measurements may be made byapplying a constant frequency to the loop input and themodulating signal to the low pass filter terminal to simulatethe effect of a FM input so that a FM generator may beomitted for many measurements.ESTIMATING DAMPING FROM MODULATINGFREQUENCY (w m ) RESPONSEPEAK AMPLITUDELOW FREQUENCY~ AMPLITUDE.3 6.0dB.5 3.2dB.7 2.2dB1.0 1.3dB5.0 .5dBW-3d8wn1.82.12.54.310* see references29
PHASE LOCKED LOOP APPLICATIONSSIGNETICS MONOLITHIC PHASE LOCKEDLOOPSDETAILED DESCRIPTION OF 5608, 5618 AND 5628The 560B, 561 Band 562B phase locked loops are allderived from the same monolithic die with different metalinterconnections. Each device contains the same vea,phase detector and voltage regulator stage and, hence, thebasic loop parameters are the same for all three circuits.The 560B is the most fundamental of the three circuits,having a block diagram equivalent to that shown inFigure 8-1. The actual circuit diagram is shown inFigure 8-19.SCHEMATIC DIAGRAM OF 5608VCC@).-----+--~-+-_o @f----I----_-t-----+---+----+---o@LOW PASSFIL TER®Qll.-----+----~------r---r---+---oQV~~i0) ~~~~~~b~TED...I----'~_+_--_+_------_O @ FM/RF INPUTVCOOUTPUT4V~---o@ DE-EMPHASIS7Vr---+-----1~--+-=-='='~"=+--+---+--+---o0VCO FINETUNE CONTROL~-I---.JVII\r--o@CRs8.2K1.2KO TRACKRANGEPHASECOMPARATOR-=- GNDGNDFigure 8-1930
Page 2 and 3: TABLE OF CONTENTSSECTION TITLE PAGE
Page 4: SECTIONINTRODUCTIONPHASE LOCKED LOO
Page 7 and 8: USER'S QUICK-LOOK GUIDE TO SIGNETIC
Page 10: SECTIONTHE PHASE LOCKED LOOP PRINCI
Page 13 and 14: PHASE LOCKED LOOP APPLICATIONSIt is
Page 15 and 16: PHASE LOCKED LOOP APPLICATIONSROOT
Page 17 and 18: PHASE LOCKED LOOP APPLICATIONSINTEG
Page 19 and 20: ~PHASE LOCKED LOOP APPLICATIONSFUNC
Page 21 and 22: PHASE LOCKED LOOP APPLICATIONSFREQU
Page 24 and 25: PHASE LOCKED LOOP APPLICATIONSGENER
Page 26 and 27: PHASE LOCKED LOOP APPLICATIONSPROBA
Page 28 and 29: ~PHASE LOCKED LOOP APPLICATIONSCapt
Page 32 and 33: PHASE LOCKED LOOP APPLICATIONSThe V
Page 34 and 35: PHASE LOCKED LOOP APPLICATIONSINTER
Page 36 and 37: PHASE LOCKED LOOP APPLICATIONSIt is
Page 38 and 39: PHASE LOCKED LOOP APPLICATIONSWhen
Page 40 and 41: PHASE LOCKED LOOP APPLICATIONSSIMPL
Page 42 and 43: PHASE LOCKED LOOP APPLICATIONSSCHEM
Page 44 and 45: PHASE LOCKED LOOP APPLICATIONSNARRO
Page 46 and 47: PHASE LOCKED LOOP APPLICATIONSTwo e
Page 48: PHASE LOCKED LOOP APPLICATIONSd.)e.
Page 52 and 53: PHASE LOCKED LOOP APPLICATIONSFM IF
Page 54 and 55: PHASE LOCKED LOOP APPLICATIONSPHASE
Page 56 and 57: PHASE LOCKED LOOP APPLICATIONSTRANS
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Page 60 and 61: PHASE LOCKED LOOP APPLICATIONSFigur
Page 62 and 63: PHASE LOCKED LOOP APPLICATIONSinput
Page 64 and 65: PHASE LOCKED LOOP APPLICATIONfTRIAN
Page 66 and 67: PHASE LOCKED LOOP APPLICATIONSRF-FM
Page 68 and 69: PHASE LOCKED LOOP APPLICATIONSVHF O
Page 70 and 71: PHASE LOCKED LOOP APPLICATIONSPRECI
Page 72 and 73: PHASE LOCKED LOOP APPLICATIONSFSK D
Page 74 and 75: PHASE LOCKED LOOP APPLICATIONSThe c
Page 76 and 77: PHASE LOCKED LOOP APPLICATIONSFLUTT
Page 78 and 79: PHASE LOCKED LOOP APPLICATIONSSALES
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PHASE LOCKED LOOP APPLICATIONSINTER
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