Lecture07_Grounding使用说明简介

1. Implications of Grounding 2. Possible Problems Hidden in a Schematic3. Imperfect or Inappropriate Grounding Examples oInappropriateSelectionofBypassCapacitor*UnderestimationorIgnoringofBypassCapacitor*BlindSelectionofBypassCapacitoroImperfectGrounding*The“LongMarch”*Un-EquipotentialityonaGroundedSurface oImproperConnection*ConnectionfromTestedPCBtoDCPowerSupply*ConnectionfromGroundtoGround 4. “Zero” CapacitoroWhatis“Zero”capacitor? ”oSelectionofthe“Zero”CapacitoroBandwidthofthe“Zero”CapacitoroCombinedEffectofMultiple“Zero”CapacitorsoChipInductorisaGoodAssistanto“Zero”CapacitorinRFICDesign Lecture 7 : Grounding Richard Chi-Hsi Li李缉熙Cellularphone:13917441363(PRC)Email:5. Quarter Wavelength of Micro Strip Line oARunnerisaPartinRFCircuitryoWhytheQuarterWavelengthissoImportant?oTheMagicoftheOpen-circuitedQuarterWavelengthMicroStripLineoTestingforWidthofaMicroStripLinewithSpecificCharacteristicImpedanceoTestingfortheQuarterWavelength Appendix o CharacterizingaChipCapacitorandChipInductorbyMeansofS21Testing Lecture#71RichardLi,2009 1. Implications of Grounding Fully grounding points : G1, G2, G3, G4, G5, G6, G7, G8 Half grounding points : Vcc1, Vcc2, Vcc3, Vcc4, Vcc5, Vcc6, Vcc7, Vcc8 Reference grounding pointFigure 1 A typical way to draw a schematic of circuitryInOutQ3R5R4R3VccQ1R2R1Q4L7R7R6L1L2G2G4G6G8G1G3G5G7Vcc1Vcc2Vcc3Vcc4Vcc5Vcc6Vcc7Vcc8GNDBlock ABlock BLecture#72RichardLi,2009 o Grounding Problems Hidden in a Schematic How to ensure all the fully grounded points being AC and DC equipotential with the reference ground point or terminal? How to ensure all the half grounded points being AC but not DC short-circuited to the reference ground point or terminal? Furthermore, if the conditions of equipotentiality, are not satisfied, the problem of forward current and return current coupling will appear. VccFigure 2 Forward and return current added to the schematic as shown in Figure 1Forward currentReturn currentGNDOutQ3R5R4R3Q1R2R1Q4L7R7R6L1L2G2G4G6G8G1G3G5G7Vcc1Vcc2Vcc3Vcc4Vcc5Vcc6Vcc7Vcc8Block ABlock BLecture#73RichardLi,20093. Imperfect or Inappropriate Grounding Exampleso Inappropriate Selection of Bypass Capacitor* Underestimation or Ignoring of Bypass Capacitor* Blind Selection of Bypass capacitor“Bypass capacitor = 0.01 F !?”“Selection of Bypass is based on performance of the block !” A huge crowded capacitorsFigure 3a A huge crowd of capacitors are supposed to function as bypass capacitorsInOutQ3R5R4R3DC power supplyQ1R2R1Q4L7R7R6L1L2G2G4G6G8G1G3G5G7Vcc1Vcc2Vcc3Vcc4Vcc5Vcc6Vcc7Vcc8GNDBlockABlockBC1= 10 pFC2= 20 pFC3= 30 pFC4= 50 pFC5= 75 pFC6= 100 pFC7= 0.001FC8= 0.01FC9= 0.1FC10= 1FC11= 10FC12= 100FLecture#74RichardLi,2009o Example #3: Inappropriate Bypass Capacitor VccTop metallic areaBottom metallic area Conductive via from top to bottomCapacitor“Zero” chip capacitorFigure 3b “Possible” RF grounding by capacitors in a pulse power amplifierInOut Pulse Power Amplifier Built by Discrete partsChip capacitor: 10 pF;Chip capacitor: 50 pF;Chip capacitor: 100 pF;Chip capacitor: 500 pF;Ceramic capacitor: 1000 pF;Ceramic capacitor: 5000 pF;Electrolyzed capacitor: 1 F;Electrolyzed capacitor: 10 F.Lecture#75RichardLi,2009o Imperfect GroundingSMASMAGNDFigure 4 “Long march” from ground at SMA input to the GND at DC power supplyOutPadinsidepackagePinConductiveviafromtoptobottomICdieICbondingpadICbondingwireRunneronICpackageRunneronPCBGroundedrunneronPCBBottomgroundedareaTopgroundedarea“Zero”CapacitorGroundofSMARunner#1Pad#6Runner#4PCBRunner#3Bondingwire#1InGroundonICdieIC Pad#3Pin#1IC Pad#4Bondingwire#2DCPowersupplyPin#13Pad#5Pad#2Runner#2Pad#1Lecture#76RichardLi,2009 o Example #4: Poor RF/AC Grounding Grounding path Ground port of input SMA connector Met#1 on the top of P.C.Board Ground runner#1 on the top of P.C.Board Pin#8 of IC package Runner#2 inside IC package Bonding pad#1 for ICdie Bonding wire#1 Ground of IC die Bonding wire#2 Bonding pad#2 for ICdie Runner#3 inside IC package Pin#1 of IC package Ground runner#4 on the top of P.C.Board Met#2 on the top of P.C.Board (Main GND reference). SMAVddSMAGNDFigure 5 An example of RF/AC grounding problems in a testing P. C. Board.Soldering pointPinsConductive via from top to bottomIC dieIC bonding padIC bonding wireRunner on IC packageRunner on P. C. BoardGrounded runner on P.C.BoardBottom grounded areaTop grounded area“Zero” CapacitorInOutMet#1Runner#1Runner#2Bondingwire#1Bondingwire#2Runner#3Runner#4Runner#2aRunner#1aMet#1aMet#2Lecture#77RichardLi,2009* The “Long March”vGroundofSMAconnectoratinputvRunner#1onPCBvPin#1ofICpackagevPad#1insideICpackagevRunner#2insideICpackagevBondingpad#2insideICpackagevBondingwire#1v ICpad#3onICdievGroundonICdiev ICpad#4onICdievBondingwire#2vBondingpad#5insideICpackagevRunner#3insideICpackagevPad#6insidepackagevPin#13ofICpackagevRunner#4onPCBvDestination:Referencegroundpoint,GND. Lecture#78RichardLi,2009BiasLGVddMBiasLGVddMZBGFigure 6 Equivalent of imperfect grounding at power supply terminal of a MOSFET transistor (The ground symbo