PCB电源设计经典资料

上海延清电子上海延清电子科技开发有限公司科技开发有限公司,,是一家专业从事高速、是一家专业从事高速、 高密高密PCBPCB设计、信号完整性设计、信号完整性(SI)(SI)分析、板级分析、板级EMCEMC设计的设计的EDAEDA技术服务提供商；技术服务提供商； 联系电话：联系电话：021021--6856666868566668 网站网站::www.yqpcb.comwww.yqpcb.com Mail:yq@ypqcb.comMail:yq@ypqcb.com PCB Layout PCB Layout on Power Supplyon Power Supply IntroductionIntroduction „„ Basic ConceptBasic Concept „„ Tips to layout Power circuitTips to layout Power circuit „„ Type of Power circuitType of Power circuit Basic ConceptBasic Concept „„ Maximum Current calculationMaximum Current calculation „„ Resistance of CopperResistance of Copper „„ ideal power supply & noiseideal power supply & noise „„ Capacitor & InductorCapacitor & Inductor „„ Power consumptionPower consumption „„ Function of power circuitFunction of power circuit Maximum Current calculationMaximum Current calculation „„ I = V/RI = V/R „„ 1 A = 1 V/ 1 OHM1 A = 1 V/ 1 OHM I=Vcc / (R1+R2) Imax <= Vcc / R1 Resistance of CopperResistance of Copper „„ Croppers=C * L / ( W * H)Croppers=C * L / ( W * H) Ideal power supply & noiseIdeal power supply & noise Capacitor & InductorCapacitor & Inductor „„ Both can store energyBoth can store energy „„ C =C =dVdV / / dIdI „„ L =L =dIdI / / dVdV S \ D Capacitor Inductor AC PASS BLOCK DC BLOCK PASS 延清电子: High frequency noise has intention to pass small capacitors 延清电子: High frequency noise has intention to pass small capacitors Power consumptionPower consumption „„ P = V * IP = V * I „„ I = P / VI = P / V Function of power circuitFunction of power circuit „„ Provide different Voltage & Current supplyProvide different Voltage & Current supply „„ Isolate noise from different function blockIsolate noise from different function block Tips to layout Power Tips to layout Power circuitcircuit„„ Find main current pathFind main current path „„ Find Feedback Node Find Feedback Node „„ Find Switching NodeFind Switching Node Find main current pathFind main current path „„ Maintain a fat main current pathMaintain a fat main current path „„ solid ground connections solid ground connections „„ multimulti--via is desired when change layervia is desired when change layer „„ Use copper if possibleUse copper if possible „„ keep capacitors in orderkeep capacitors in order „„ for some switch power circuit, tight GND for some switch power circuit, tight GND to plane at one pointto plane at one point Find Feedback NodeFind Feedback Node „„ High impedance inputHigh impedance input „„ keep short as possiblekeep short as possible Find Switching NodeFind Switching Node „„ The noisiest nodeThe noisiest node „„ keep as short & fat as possiblekeep as short & fat as possible Type of Power circuitType of Power circuit „„ DCDC--DC converterDC converter „„ Linear RegulatorLinear Regulator „„ Power filtersPower filters „„ Switching RegulatorSwitching Regulator „„ Switching power circuit with isolationSwitching power circuit with isolation DCDC--DC converterDC converter „„ Some with control & FeedbackSome with control & Feedback Linear RegulatorLinear Regulator „„ Input current is as same as output currentInput current is as same as output current „„ P(heatP(heat)=()=(VinVin--VoutVout) * I) * I „„ If If P(heatP(heat) >1W, heat sink or copper attached ) >1W, heat sink or copper attached to tab is desired. If tab pin is connected to to tab is desired. If tab pin is connected to ground or power output, add multiground or power output, add multi--viasvias to to plane for thermal dissipationplane for thermal dissipation Linear Regulator (continued)Linear Regulator (continued) Power filtersPower filters „„ Low pass filterLow pass filter „„ RC filter, LC filter and PI filterRC filter, LC filter and PI filter Power filters (continued)Power filters (continued) „„ MultiMulti--stage filtersstage filters Power filters (continued)Power filters (continued) Power filters (continued)Power filters (continued) „„ Power for PLLPower for PLL Power filters (continued)Power filters (continued) „„ Power for PLLPower for PLL Switching RegulatorSwitching Regulator „„ The most effective circuitThe most effective circuit „„ How does switching regulator work?How does switching regulator work? Switching Regulator (continued)Switching Regulator (continued) Switching Regulator (continued)Switching Regulator (continued) Switching Regulator (continued)Switching Regulator (continued) Switching Regulator (continued)Switching Regulator (continued) Switching power circuit with isolationSwitching power circuit with isolation „„ Keep 50 to 100 mil clearance to internal Keep 50 to 100 mil clearance to internal circuit on all layers.circuit on all layers. „„ Add spacing area constrain to TNV Add spacing area constrain to TNV section. section. „„ Keep switching node as short as possible.Keep switching node as short as possible. „„ Use multiUse multi--layer and multilayer and multi--via for high via for high current path.current path. „„ Make default trace wider (10 mil) . Make default trace wider (10 mil) . „„ Force power input hit bypass first. Add Force power input hit bypass first. Add moat if necessary.moat if necessary. „„ Keep protection circuit close to Keep protection circuit close to transformer.transformer. „„ Identify power and ground for switchingIdentify power and ground for switching Switching power circuit with isolationSwitching power circuit with isolation ConclusionConclusion „„ Power supply is essential in PCB design. A Power supply is essential in PCB design. A noisy power supply can lead to failure noisy power supply can lead to failure debugging.debugging. „„ Try to routing Power section first to avoid Try to routing Power section first to avoid lack of room.lack of room. „„ Due to different board geometry and Due to different board geometry and constrains to the placement, circuit constrains to the placement, circuit require quiet power and ground plane require quiet power and ground plane may be on the way of high current path. may be on the way of high current path. Moats can be added to force current away. Moats can be added to force current away. „„ In case two inductors have to be close, In case two inductors have to be close, try to place them vertical to each other to try to place them vertical to each other to avoid interference .avoid interference .