DGM-1040

DGM-1040_15 AD | Alldatasheet

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08/25/9415:0011'9106680101 ANALOGDEVICES ~002/005 --.COMPUTER LABS ..'!LIllIANALOG DEVICES DGM-1040 and -1080 OfA Deg litchers General Deglitchersare normally used to eliminatethe non-lineareffects of "glitches"from the output of D/A converters. The Computer Labs DGM Series of Deglitchers may be used with almost any type ofD/A convertertogeneratean out- put signal with extremely high spectralpurity.These Deglitchers have been used fortelevisionsignal. reproduction,CRT displays.wave- Iform generation,and automatictest Iequipment, to name a few. I I The Problem In most instances,fast-settling DIA convertersare current-switch- ingtypes,ratherthanvoltagetypes. In thistype of converter,any input bitchanging causes a change inthe output current of the converter. The input circuitsforcurrent- switching 01A's,and theirTTL or DTL drivinglogic,are subject to the characteristicofsaturatedlogic which causes propogationdelayfor negative-going inputs to be dif- ferentfrom the delay for positive- going inputs. As a resultofthisphenomenon, time skew of the individualcurrent switches withinthe D/A converter is worst when one or more input bitsareoutof phase withthe others. This istrueeven foridealinputsin which the digitalinput bitsarrive simultaneously;if there is time skew among the bit inputs,the problem becomes even more pro- nounced. These differencesamong the internalswitches cause a discon- tinuityor "glitch"in the output currentof the D/A converter.The true "worst case" glitch always occurs at theswitchingpointofthe Most SignificantBit (MS8) or the center point of the output range, because nearlyequal and opposite currentsare being switched. In additionto thisinescapable switching transientin the output, Featu res . 15 nsee acquisitiontime. .0.01% linearity. .Directlyinterfaceswith ultrahigh-speed,current-outputD/A's. . TTL or ECl compatible. .DGM plus D/A costs lessthan any "degfitched" O/A available, .f:'!.-,sw t SQuRC£J.. .l ""ALOO,"-, 50 I I.~""'V ~'-"... ~ .5v ben(') 1'0~ -O.ZV I I-5.lv _5~--l~ " J,I.O.12,16.Z0 ~ ~O"'T1:.'.'1£CL (Cl TTL/£CL COIOV(lI'I'co ICI'TICD1&j,J TO D/& 0IITf'UT -$~ V -,lSC"..£~- ..""UST :SI.I O£CLlTeD "FUSCa."~r 0- TTL. -IS W ""'1£ I)., ",,1£:,. TD(S[ PI"O UDUS£O IF (Cl.I'\\ITOPTia. 1$ $(lECT£D. DGIo4 SERIES 8L.OCIO: D IAGRA.IoI - -- - - OBSOLETE

08/25/9415:01'a'9106680101 most current-outputD/A converters alsohave a maximum outputvoltage limitation. Part of this limitationmay be the resultof high output capacit- ance and/or resistance;thischar- acteristiccan be "masked" in data sheets ifsettlingtime is specified with an impractically-low imped- ance load. Even D/A converters which have low output capacitance and/ or resistance willhave a maximum output voltage limitationwhich is established by saturation of the internalswitching transistors. This internal saturation, in turn,generallyprecludesoperating the current-switching D/A con- verteras effectivelyin a unipolar mode as itcan be operated ina bi- polaroutput mode. NOTE;.:Addlt;o~ald.f.il.on 'ha cnar8ct~(i~'iC5cf current- Ih. oale Sneel on Ihe Compu'er lab. MDSfMDP $e,les O/A'S. The Solution When firstexposed to the un- desirable effect of analog dis- continuitiesin the outputs of cur- rent-switchingD/A converters, many users erroneously assume two straight-forward approaches will solve the problem. At the in- put, minimizing time skew among the data bit inputswillbe a use- ful technique. At the output. the use of a filtermay also appear to be a neat "solution"to the problem. Unfortunately. no amount of time alignment on the input bits will overcome the physical laws associated with the propogation delays of saturated logicdiscussed earlier.In addition,a filterdesigned for eliminating the "glitch"at the major carry point will not be optimized for transients at other points of the output, nor will it change the relationshipof transient amplitudes; this is because the glitchisa function of signal dyna- mics. AS a result,a multitude of intermodulation products are form- ed; some of these 1M products ap- pear in the video pass-band as spurious signals, and increased noiselevel. Besides these considerations, no amount of minimizing time skew ANALOGDEVICES AC CHARACTERISTICS DGM-1040 AcquisitionTime Sample Rate (max) Sample Delay TTL ECl 15 nsec

30 MHz

6 nsec . I4I003/0~ DGM-10aO 75 nsec

11 MHz

60 dB >60 dB 10 mV 30 mV 0.2mV (AMS) See Fig,2&3 s~ Fig.2 ,mY/usee >60 dB >70 dB 2 mV $"" Fig.1 20 mV S""FiQ.1 0.1mV (RMS) DGM-1040 & DGM"1080 DC CHARACTERISTICS Gain Offset OffsetDrift Linearity CurrentSource Current CurrentSink Current .975 Adjustable to zero 100 ppm/oC :1:0.01% 7.5 mA max 19 mA max ANALOG INPUT CHARACTERISTICS Input Voltage i:2V Input Impedance 1 megohm Input Bias Current 0.05 nA ANALOG OUTPUT CHARACTERISTICS Output Voltage (no load) :1:2V Output Current :!:SOmA Output Impedance 50 ohms DEGLITCH STROBE CHARACTER ISTICS Optionallyeitherofthefollowing: TTL singlelineinput "0"= track "1" =hold ECL 2 linecomplementary "0"= track "1"= hold 0 to +0.4 V 2standard +2.4to +4 V TTlload! -1.7 V The.e inpu,,"a'e".ch terminated -0.8 V wit" a 330 ohm pull- down ,a~l~torto .5.2v. POWER REQUIREMENTS +15 V @ 100 mA w/o currentsource connected -15V @ 100mA w/o currentsourceconnected +5 V @ 20 mA }TTl input option-5.2V @ 80 mA -5.2V @ 24 mA ECl input option. PHYSICAL CHARACTERISTICS Package Size 2.3"by 2.3"by 0.43" 58 mm by 58 mm by 11 mm Weight Pins Case 3 oz ~5 grams 0.040 diameter gold plated diallylphthalate per Mll-M-14 type SDG-F OBSOLETE

~OOP ~UA" GLITCH --,---- I FIG, I DGM OUTPUT -DC INPUT 08/25/9415:01'5"9106680101 DGM f PEDESTAL. OUTPUT WITH DC INPUT? .-.., OEGLITCH -1-MOLD INPUT "0" TRACt( OIl. CATA CHANGING DATA INPuT ST~ADT GLITCH PERIOD~ , ANALOGDEVICES DEGL.ITer ~ INPUT:L J -"-1 ANAL.ex; OUTI"IJT OF DIA FINAL SECOND VdLUE INITIAL. VAL.uE ANI.LOG OUT OF DGM 1 ~ ACOUISTION I TIIoIE t 1"/. OF fiNAL. VAL.uE INITIAL VAL.UE-- J L SAMPLE "I r DE:L.oI.Y DGM FIG,2 OUTPUT - D/A INPUT 0.' I", ~T "., I',. AT 7~ .s O.l~ ~ 0.2 a ~ DGN-IOeo oCo T."e ii'O.I~ isu It 01 '" 0 O' ..o:oe 0.07 o.o~ 0.0' 0.0. 003 0.0lO.OJ 0.00 0 00" 20 73 100 ". .COUISIT,ON TINt (N"(,1 FIG, 3 ACQUISITION TI~E V$. Sli:TTUNG ACCURACy .11 ....0" fl j 1.11 .. '0 W , 1,. ::: oono."c. :: ~',~a.a. , J ""'" .'. .. ' ::: ~: . ..~,~ I lOa O.i 0.' ;i g 0.0 ~ 0.< 8..'" Ol .. g I'r. 141 004/005 and/or filteringthe output will overcome the output voltage limi- tationsimposed by internalswitch- ing transistorsaturation. An optimum solution to the problem of glitches would cause the glitch to remain constant, re- gardless of the transition points on the input data.As an example, it should remain the same for the transition from a 000 000 001 to 1 000 000 000; as it is for the transition trom 1 000 000 000 to 1 000 000 001; or any other two input words. Ideally,an optimum solution to the glitch problem would also permit using the fullcurrent drive capabilitiesot the current-switch- ing D/A converter in both bipolar and unipolar modes ot operation. The purpose of the Computer Labs DGM modules isto reduce the amplitudeoftheglitchtoan accept- able level,and more importantly,to provide a constant-amplitude glitch. This will hold the area under the curve at a constant value; the modules are not intended to get ridof allglitchesper se. When the area under the trans- ient curve isheld constant, the fre- quency spectrum of the glitchisa fine line,i.e..a single-linespectrum at the sample ratefrequencies.and harmonics of the sample frequency. The deglitcher circuitseffect. Iveryeliminate the intermodulation products discussed earlier.When they do. the SIN ratioapproaches thatof an ideally-quantizedsignal. where the rms noise is q/ v'l2. when frequenciesabove Nyquist arefilteredout. The DGM modules also in- corporate an internaladjustable currentsink.toadjustthe D/A out- put for bipolar operation. In ad- dition, an internal voltage shifter consistingof a current source and a precision resistor allows using the bipolaroutputdrive capabilities of the DfA converter for unipolar positive applications. These fea- tures permit OV to +2V unipolar outputs. An internalbufferamplifier buffers output loading from the D/A module. permitting a constant SO.ohm output impedance. Non,: Ado."onoi ,nfO<n\\al;On~nd piclurc~ on dcg"IC~1n9 OBSOLETE

..'STROBE ..J Z <liS ,-", ai:>.. -0...Gl:N <;>:: 'C; STROBE 15:02'a'9106680101 ANALOGDEVICES ~005/005 13.I:I,COW"ON VI ...:>C1. ..J<r- iac .... I-CI') C!)I>l a:: OUTPUT MDS -OElIS~ .... (I) ... .... CIA CONvERTER CLOCK OFFSET ADJUST 1000 L 1:11'5 I--(MINI -IS V BIPOLAR ANALOG OUTPUT SO Okllll 0.1 V no-PILINE SO A v0 IOP~[tTi ' ~I,4 V (P-PI Co :501\\. SETT\\,ING TII.'E:. 20 NS "'.!loX,UPDATE RATE - 30 MHl DISTORTION < 0,1 '/, L.!IoIiGESIGNAL BANOWIDTHS UP TO 15MI1Z ULTRA FAST OEGLITCHED CIA CONFIGURATION REF'N +v ,REFOUT 4)0"- t.4DSL-0825 OR MDSL- 1035 CIA CONvERTER IOUT !IV ANA\\,OG SIGNAL 1600AI <p~S J -.J L ~ 45 /oISI-- (MINI tDATA UPOATE SYNCHRONOUS wITH I.£ADING EDGE: OF STROBE OFFSET .!IoDJUST 1000A ZI O'rO+IV 15 OHIO! VUIE:O LINE SIGNAL 50 jl 24 J>. 20 7SJI. OGM-1040 DEGLITCH MODUI..E OUTPUT: 0 TO +I VOLT INTO 1S JI. SETTLING TIME' 20 NS MAJ(. SAMPLE: !lA-TE' II WHZ DIFF, GAIN ~4"1, '881T51 ~ 2 ":t. (9 BIT51

2 I % 110 BITS)

DII'I'.PHASE: 1: 2 eEG. <s BITS! ~ I DEG. (9 BITSI ~ 0.5 DEG. (10 BITS) DEGLITCHEO CIA FO~ TELEVISION SIGNAL REPRODUCTION

ORDERING INFORMATION

DGM-1040 or DGM-1080 arenormally supplied with TTL "d~ glitch"input.For balanced ECl input,specify ECl Input on P.O, or add suffix"ECl" to part number. ,..COMPUTERLABS ANALOG DEVICES COMPUTER LABS. A DIVISION OF ANALOG DEVICES ANALOG DEViCeS. ROUTE 1 INDUSTRIAL PARK. NORWOOD, MA 02062 .(617) 329-4700 .TWX 710-394-6577 - - - - - - --- 14 21 11 O DGM -1040 OEGLITCH MODULE IS 11 OBSOLETE