g. The maximum skew introduced by the cable between the differential signaling pair (i. This routing width rule targets a class of DRAM nets. 0 interface. 16 mil. $egingroup$ So basically your answer shows that the JLCPCB impedance calculator results are generally in the same ballpark as the proven field simulators. Yes, that's right. In general, it is double the odd-mode impedance, which is the value we care about for differential signaling, as it is used in high-speed PCB design. With the Multi-CB impedance calculator, you can calculate the approximate impedance dimensioning of your PCB / high frequency circuit board. The differential impedance. The required values are trace thickness, substrate heights, trace width, and subtrate dielectric in the calculator above and press the "calculate" button. 35mm prepreg, 8mil track width, 8mil spacing → 100Ω impedance. The differential impedance of a PCB is simply the current to voltage ratio on pairs of transmission lines driven in differential mode. THESE FORMULAS ARE APPROXIMATIONS! They should not be used when a high degree of accuracy is required. PCB Structures / Discrete Structures / Signal Management. 5 mil (2116 prepreg) or 8. Our impedance calculator features two main types of impedance models, single-ended and differential, within each trace structure. 5oz inner copper, 8 mil trace spacing) and a target differential impedance of 100 ohms, JLC's calculator suggests a trace width of 8. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. One of the features of this type of microstrip is the coupling between lines. SET2SEIL. g. There are many calculators available online, as well as built into your PCB design software. The differential impedance of MIPI tracks should be 100 Ohms, not 90 (USB requires 90). Saturn PCB - Toolkit for Impedance Calculation. 5mil clearance on a 63 mil board (1. Altium Designer’s differential line impedance calculator will set up your impedance-controlled differential pair routing widths for you. 254mm. 0 and CAN-FD might be slow enough to get away without it (and I'm honestly not sure, the performance will depend on the specific configuration), but if I were reviewing a layout with diff pairs without a ground reference I would be very unhappy with it. Against the two rows select the. Atlas Si for VNA – Insertion loss test system – Delta-L 4. 5 mil wide traces with about 6 mils of. The same applies to differential pairs. The following options in the Options for PCB Project dialog are used to configure this:. There are some signal integrity issues with de-skewing in traces: Impedance. PCB impedance calculator – Single ended / Differential pair PCB manufacturer normally provides information about PCB stackup and track geometry. You want to select “Microstrip Zdiff”. 75 mm track on a 0. 52mm fr-4, 1oz cooper) and a target of 90ohm differential impedance, i calculated a value of about. This is the impedance between the two signal traces of a pair. Trace width and spacing depend on your PCB stackup. Skip to main content. This is not usually a routing rule a designer might consider unless they are doing something very intentional with RF design, or they are routing differential pairs that require a specific impedance. For more information see "Interactively Routing with Controlled Impedances on a PCB in Altium Designer: Routing Width Design Rule" in the official documentation. Polar or rectangular grids only allow direct reading of S11. I would use a stackup like. This coupling lowers the differential impedance between the traces. I am designing a flexible PCB to carry two types of differential signals. 6mm PCB you are looking at traces nearly 3mm wide and then you'll need distance between them to make differential pair. 9. Typically, when beginning the impedance calculation, the smallest trac e space (4 - 5 mils) is selected. Units ( mils ) Show PCB Dielectric Material. ALTIUM DESIGNER. This tool calculates the crosstalk. Procedures: Use differential impedance calculator to determine transmission line geometry for given differential impedance Zdiff=90 Ohms (impedance seen between two lines of a pair). While there are a number of online calculators that calculate the characteristic impedance from the input geometry, they are all based on approximations. The same figures put into pcbway's calculator give me 115R, and the same. Assuming the differential pair I am routing is requiring 90 ohm (this is what the hardware guideline say "Route the USB differential pair on the top layer with a trace width and differential spacing tuned to the PCB stack-up for 90Ω differential impedance "). For example, ECL logic has a 50 Ω characteristic impedance, and TTL has a source impedance range of 70 to 100 Ω. Engineers pressured fabricators to create circuit boards with 50 Ohm impedance. The online menus contain a calculator to help you to define the correct track and gap values for your layout, for example for 50Ω characteristic and 90Ω differential impedance using. This is good for routing space, but not so good for power delivery if there is a need for interplane capacitance. Critical Length. Characteristic impedance or surge impedance is the impedance of a PCB transmission line without including the effect of other transmission lines. The weave is much too coarse which means that as the pair runs along the board, the impedance changes continuously due to the dielectric constant varying. Just as important as determining an appropriate trace width for a single-ended trace is determination of an appropriate spacing between two traces in a differential pair. 25, but gives me nice trace from the module to the stub then to microcontroller. – Microstrip lines are either on the top or bottom layer of a PCB. 5; w, t, s, h > 0;Made in Europe. beammy. Similar notes exist for other devices but USB is the one I'm most interested in. Differential Pair Impedance Calculator Calculates the differential pair impedance of a balanced line. PCB Stackup Impedance Calculator Calculates the characteristic impedance per unit length parameters of typical Some of the common Dielectrics & their values: Relative. Value of Zo calculated by impedance calculator is not relevant here. Differential pair on a reference plane for differential mode (left picture) and common mode (right picture) line impedance In addition to the four line impedance types the Impedance Calculator is also able to calculate the Coupling Factor between two traces on either the same signal layer (horizontal coupling) or between two traces on different. KiCad has a built-in impedance calculator!Maximize System Performance With LVDS PCB Layout Guidelines . Remember, the lower the impedance the greater the current drain, the higher the. Grounded Differential Coplanar Wave Guide. Typical impedance tolerances are 10% and 7%, and can go as low as 5% or 2%. . By controlling the PCB impedance, unexpected damages or errors can be limited to some extent. The PCB Impedance Calculator in Altium Designer. Sample coupon — Gerber Data mpcd1345. H 2 H 2 = subtrate height 2. If T R = 100pS. At some point the amplitude will stay constant. g. So unless you carefully design your routes within your PCB, the impedance would be uncontrolled, and its value. trace geometry, and use this to calculate. H1: Height of the dielectric between the trace and the reference plane. Insertion Loss. Rule setup for differential pair (100 ohms) routing using Altium Designer. On an impedance controlled layer (for example, with 100 diff), find an unused area and run a differential pair and expose at each end to the surface with test pads. Take account, the internal used formulas sometimes don't equal on Conductor Impedance tab and on Differential pairs tab (e. ) and the LOW level is defined as zero. 3 as fr4 material with 1. Single-ended impedance of 50 Ohm. Edit: also, think ahead if you are going to use ground pours around the traces. So my first prototype board had some issues with usb connectivity due to me not knowing anything about differential pair routing, matching/coupling and impedance control. This calculator helps translating the color bars from the resistor to its value. The trace width (0. It is the ratio of voltage and current amplitudes of a single wave propagating along the line in the absence of reflections from other directions. To have designs be robust from PCB manufacturing errors and defects design the traces impedance be as close to the recommended value. The calculator shows 90 ohms can be achieved using. 25mm, a trace width of 0. Chrome 92. One of the features of this type of microstrip is the coupling between lines. ; Edge coupled differential pair ; Edge coupled internal symmetric differential pair ; Edge coupled internal asymmetric differential pair ; Edge coupled embedded differential pair ; Broadside coupled shielded differential pair Overview. Such a microstrip is constructed with two traces referenced to the same reference plane with a dielectric material between them. In “Eaglelake platform design guide”, Intel recommends 95Ω±15 % differentialThe Si8000m adds enhanced modelling to predict the finished impedance of multiple dielectric PCB builds and also takes into account the local variations in dielectric constant on close spaced differential structures. Microstrip Impedance Calculator. The High speed protocol that is being designed for determines what the single and differential trace Impedance the traces need to meet as well as the tolerance for the impedance (e. Speedstack Si – Insertion loss & impedance PCB stackup design including Si9000e. I've learnt about it now and using my pcb specs (1. g. Right-click and choose Change from the pop-up menu. The impedance calculator determines the signal properties and clearances (first image), use that clearance in the via shielding Distance setting. Such a microstrip is constructed with two traces referenced to the same reference plane with a dielectric material between them. Note that the net pair must be named with net label suffixes of _N and _P. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. This calculator is designed to calculate the characteristic impedance of an edge coupled stripline. Supports Anritsu ShockLine™ MS46524B and VectorStar™ MS4647B. (5mil prepreg) But in your case if using a 10 mil dielectric; Impedance is almost constant ratiometric to the conductor geometry ratios if <2:1 ratios for planar and < 3:1 for differential coplanar. One of the features of this type of microstrip is the coupling between lines. 50 - 55 ohms). Differential Pair Calculator The Differential Pair Calculator is used to perform what-if analysis to determine what values of Primary gap and width are needed to get specific differential and single line impedance. too. 0 and 0. 2. PCB DESIGN TOOL Impedance Calculator TRY TOOL . L1=Ground, L2=signal/transmission lines, L3=signal, L4=Power. 3. Remember, the lower the impedance the greater the current drain, the higher the. 6 mm; resulting differential impedance: 100 Ohms; IBEX. When you are creating your schematic, you must use one of the following suffixes when naming your differential pair nets: +/- (e. Thus, for optimal performance the resistors and MOSFETs must be matched. The Si8000m assumes negligible insertion loss in the transmission line; should you wish to model insertion loss the Si9000e adds. PCB Coplanar Waveguide Calculator RF PCBs can be complex boards that need careful interconnect design and layout. The surface finish is neglected. If trace width is increased for the metal losses reduction, the single end impedance will be reduces. BGA land calculator based on the IPC-7351A specification. differential impedance accurately In order to have maximum coupling of the magnetic field lines, the space between two conductors of a differential pair should be kept to a minimum. So, strive to keep your traces short and far apart in high-speed design. 1<W/H<3. One is about 1. Using these highlighting methods, you can quickly highlight all differential pairs in a particular. 6193. Differential pair into PCB calculator. But it lacks the differential impedance (impedance between these two tracks). Using the KiCad Impedance Calculator. I am using Altium Designer and it has a nice impedance calculator which tells you the required track width for a desired impedance given the layer stack you have configured. 1. The trace width is then adjusted to achieve the neces-sary impedance. 4 ohms; differential impedance: 90. For differential vias, stitching vias can affect the impedance, but the impedance is much more sensitive to antipad sizes and layer arrangement/Dk value on each layer. Added edge coupled embedded differential pair to calculator. Perhaps the most common type of transmission line is the coax. The screenshot is as shown in the picture q1-pro-pcb. 1 Answer. D+ and D-) _P/_N (e. To be precise, the current flows through the. 90 Ohm Differential Pair: 0. To answer, Zac. Single-Ended Impedance The trace impedance (single-ended) in an individual trace is normally calculated by ignoring any neighboring traces, so no coupling to other conductors in the design will be included. The two points at the beginning of the pair might be weakly coupled, but adding or removing some copper at the source end allows you to match pair lengths while ensuring common. Controlled differential impedance starts with characteristic impedance. This resistor is invisible to the even mode signals as the even mode content on each track is identical so no even mode current flows in this resistor. g. Once you know the characteristic impedance, the differential. pH nH uH mH H kH. We’ll go over how differential pairs can hel. , the via is electrically short). 8 mm to 0. The impedance of a differential pair depends on the self capacitance and self inductance of each trace, and the mutual capacitance and mutual inductance between each trace. The HIGH level is brought up to a logic level (5 V, 3. When you need to do trace length matching in PCB design, your goal is to minimize timing differences between traces in a length-matching differential pair in a serial protocol, multiple traces. Distance between tracks (s) = 254 micron. The S50 Impedance Profile is defining the routing widths, which will change according. 4. 5 to 4. 34, 40, and 48 Ohms single-ended impedance are common, and each of these will have a specific corresponding differential pair impedance. At that point the rest of the description is missing, which includes wire diameter, insulation thickness and dielectric constant, and the number of twists per inch or other unit of distance. Grounded Differential Coplanar Wave Guide. There are many demands placed on PCB stackup design. It shows the minimum trace-to-ground spacing required to. Tech Consultant Zach Peterson is talking Signal Integrity again today with a deep dive into Differential Impedance. The following are typical line widths and spacings for the more common impedance values when using ½ OZ copper: 50 Ohm Single Ended: 0. This sets the single-ended impedance AND differential impedance to the target value, even if there is no. Just as important as determining an appropriate trace width for a single-ended trace is determination of an appropriate spacing between two traces in a differential pair. Differential Stripline Impedance Calculator. Differential pairs with vias and right-angle bends are acceptable. The differential impedance will be a bit less than 2x the single-ended impedance. In other words, if you are designing to hit a differential impedance target (such as. From here, we can see that there are specific stack-ups where a CPW and a microstrip/stripline will have 50 Ohm impedance and the same trace width, even though the ground clearance is quite close clearance to the trace in the CPW. Either the desired impedance at a specific frequency is used to determine the waveguide width, or the width is entered and the impedance is calculated. Here, we are using a USB 2. 9. Figure 5. 50 Ω±15%). The controlled impedance lines should be marked in the PCB schematic drawing. Rs =. They are very simple to read, and the values in. Differential pair impedance depends on a lot of variables in reality,. Figure 1. Spacing and width value pairs that will give a differential impedance of 100 Ohms on Dk = 4. These parameters include:This is eight layer stackup. There are a lot of online trace impedance calculators specifically designed for differential traces. So my. 4mils = 0. There is only one method I am aware of that gives any level of accuracy for differential via impedance calculations, and it starts from a calculation of the propagation delay through a pair of differential vias. I make that clearance at least 3 times the distance from your diffpair to its reference plane (i. 75 mm track on a 0. If the calculator does not provide velocity (or velocity factor), it's probably because you can use e_eff instead. Advertisement Board thickness (h) = 50 micron. If you can - Use a 0. which is 0. Added edge. The example below shows how adjusting the stitching via placement could affect a differential via. nm um mm cm m mil inch. 2. Note that the y-axis is on a logarithmic scale for clarity. Differential impedance is another factor you should probably consider when dealing with impedance. Eurocircuits also calculates the correct Differential Impedance values using the correct formula and not a ‘Rule of Thumb’ method. A pair of lines can be modeled as follows: Differential pair line. 4. > A good starting point is to ask you board house give you the widths and spacing for your stackup. The differential pair trace lengths should be matched with a tolerance of 20% of the signal rise/fall time. To access the differential calculator, in the Primary Gap, Neck Gap, or +/- Tolerance cells, do the following steps: 4. 100 ohm differential pairs that are tightly coupled have a typical single ended impedance of around 65 ohms. 1. infinite mutual impedance. For the signal trace of width W and thickness T, separated by distance H from a ground (or power) plane by a PCB dielectric with dielectric constant εr, the characteristic impedance isEdge-coupled coated differential microstrip Edge coupled differential microstrip for flex PCB. I am trying to design a CAN bus node. For example: Yellow Violet Red Gold: 4 7 x100 ±5% = 4700 Ohm, 5% tolerance. $endgroup$ –The microstrip impedance represents the characteristic impedance of the microstrip line. Defining the Differential Pairs on the Schematic. Differential Pair Routing. LVDS PCB layout guidelines aim to ensure optimal signal integrity and minimize noise interference by considering factors like impedance control, differential pair routing, grounding, etc. 48 mm FR4 thickness. KiCAD doesn't have a calculator for differential coplanar waveguide. We recommend. In tab “TransLine” i chose “Coupled Microstrip Line” and i can calculate the impedance of only one track. Some differential impedance requirement for differential pairs, where the signals must be routed together Just as an example, consider a 2-layer board on standard thickness 62 mil core (Dk = 4. When working with differential pairs, your trace spacing and geometry will determine the impedance of each trace and of the pair. If trace width is increased for the metal losses reduction, the single end impedance will be reduces. 004” line/0. Differential pair impedance depends on a lot of variables in reality,. This video explains the most common layout topics for USB signals: impedance, trace length and matching, and printed circuit board (PCB) stack-up. There are two design rules that are obeyed during length tuning, the Matched Length rule and the Length rule, both are in the High Speed category in the PCB Rules and Constraints Editor. Going to route the following signals: 100R differential pair (Zo = 50R) 90R differential pair (Zo = 45R) Planning to use the stack up JLC7628, with a 4 layer PCB, in total 1. 0 mils and h = 8. In tab “TransLine” i chose “Coupled Microstrip Line” and i can calculate the impedance of only one track. when i use Saturn PCB design to match the differential impedance to 100ohms i get 0. e. The calculator is available in the Electrical Domain in Constraint Manager, from theDifferential Stripline Impedance Calculator. To calculate geometry for 90OHMs Differential pairs routed on 2 layer PCB (Differential impedance of Microstrips) you need to know: width of the traces, space (gap) between the traces, height of dielectric above return plane, trace thickness and relative permittivity of the dielectric. Either or both of these rules may be important in your design, it all. To get the correct parameters, we have to use the specifications from our PCB house and the provided calculator. 3 * 1. THESE FORMULAS ARE APPROXIMATIONS! They should not be used when a high degree of accuracy is required. g. Embedded Microstrip Trace. For context, as I understand it, the Ethernet pairs between the PHY and magnetics need to be impedance controlled to 100ohm and they need to be routed (ideally) in parallel, and the trace space and trace width are important variables in the impedance control. The typical impedance should be a 100 Ohm differential with a +/- 10% control. 5mm pitch has about 100 ohm differential impedance in the configuration where a differential data pair wires are between ground. The values you get from an online differential pair impedance calculator corresponds to an isolated differential pair, they do not consider the load component and they are not calculating the input impedance. On the top layer and I have 50 ohm impedance for single ended signals with a trace width 7. The S50 Impedance Profile is defining the routing widths, which will change according. Re: USB differential pair on 2 layer board. At the receiver, the signal is recovered by taking the difference between the signal levels on. If they aren't that high, then don't worry about matching on the PCB, but use. Also note that your best bet may actually be VERY SHORT (few mm) traces, a thinner board or a 4 layer board :-) Thanks for your suggestions. Similarly, external fields can induce currents in a differential pair that are not. beammy. 0037” line/0. Differential Microstrip Impedance From Zo. 4mils, w = 12. (to the next pair and to the ground plane. 8 core of FR4 material, we would have a propagation delay of approximately 150 ps/inch, or approximately 6 inches/ns. Most high speed signal protocols, such as PCIe or Ethernet, use differential pair routing, so you need to design to a specific differential impedance by calculating trace width and spacing. PCB Coplanar Waveguide Calculator RF PCBs can be complex boards that need careful interconnect design and. So move to your left, use Omni's Cable impedance calculator and enjoy. Calculates the differential pair impedance of a balanced line. The characteristic impedance of the microstrip line means that is the uniform impedance provided by the uniform cross-sectional dimensions along the microstrip (flat copper conductor) length; to prevent signal reflection. It worked for a while, then it began destroying random devices, obviously because of other design errors. If you’re designing an RF PCB for. The ICD Stackup Planner calculates characteristic impedance plus edge coupled and broadside coupled differential impedance. T T = trace thickness. 81. But for extreme geometries and for many differential pair structures, these approximations can. P/N De-skew Strategy on Differential Pairs. The designer needs to create a stackup for the board and then calculate the trace values for differential pairs and single-ended nets. The correction can be done with the menu option: Route → Tune Differential Pair Length Skew/Phase. 331 1 2 5. Crosstalk Area. • A single differential pair should be routed as close together as possible. Eurocircuits’ PCB DEFINED IMPEDANCE pool is a fast turnaround solution for PCB’s with a specific impedance requirements for certain tracks. This is more than the to times trace width which is recommended (also read as close as possibly). png . Unfortunately, stating “should match the input impedance of the differential vias/pads” in Point #3 is easier said than done. g. Modeling approximation can be used to design the microstrip trace. With PCBWay impedance calculator, you can calculate the approximate impedance of your PCB / high frequency circuit board. High-speed designs carry a requirement for controlled impedance, crosstalk control, and the need for interplane capacitance. The microstrip is a very simple yet useful way to create a transmission line with a PCB. Microstrip Width Calculator. Enter the relative permitivity, width of the trace, the ground plane spacing, and the substrate thickness to calculate the characteristic impedance. The single-ended impedance of a trace in a differential pair will depend on the distance to the other trace, and applying a length-tuning structure is equivalent to changing the distance between the traces while meandering. The same in true for bottom layer. While it is not necessary or a requirement to match the PCB 'stubs' it's probably a good idea if the speeds of your RS485 bus are high (+50MHz). Most formulas calculate impedance from width, because width is a boundary condition and it's easier to calculate forward from a boundary condition, than backwards to reconstruct it. LVDS PCB layout guidelines aim to ensure optimal signal integrity and minimize noise interference by considering factors like impedance control, differential pair routing, grounding, etc. USB traces must be 90 Ohms differential. The idea here is to determine the spacing required for a given width with the goal of hitting a specific differential impedance value. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. Using the built-in Simbeor ® impedance calculator, the PCB editor's Layer Stack Manager calculates the trace width needed to deliver the specified impedance. 1,481. Implementation of these guidelines can help designers maximize the performance of the LVDS-based system across a wide range of applications. Just as was the case with microstrip impedance calculators, stripline impedance calculators tend to rely on either the IPC-2141 formulas or on Wadell’s equations. 0055” spacing. Not too tricky. The characteristic impedance of your microstrips is determined by the trace width for a given layer stackup. 006” space to be 100 Ohms differential” please make sure that the specified geometry is present on ALL the signal layers. Therefore i tried using this paper to calculate a characteristic impedance of 60Ohm for a coplanar strip attaching the CAN-Transceiver to a Twisted Pair cable, the CAN bus medium. Assuming both. Let's match the impedance of the same signal since differential pair routing is completed when the impedance is matched properly. 1 mm. Zeven: This is the even-mode impedance of the differential pair. **Note: Like our stripline impedance calculator, all of our RF calculators allow SI prefix input. Follow the 8W spacing for differential clocks (or explore other rules) Even greater spacing is needed for high-speed differential signals. H eff = H 1 + H 2 2 H e f f = H 1 + H 2 2. Impedance and PCB Stacking The trace impedance is affected by many factors such as the width of the trace, th e thickness of the copper, the PCB material, the PCB stacking specification, and the spacing between the differential pairs. Development Kits. Use several of them and compare. arrow-right Download and install the Analog Engineer's Calculator. USB traces must be 90 Ohms differential. When selecting trace geometry, priority should be given to matching the differential impedance over the single ended impedance. In many application notes how to make an Ethernet interface, the wiring. Also, be aware, 90 ohms is the differential impedance, the characteristic or single ended impedance will be more than half (ie. I have one differential pair in the transmission line. Color-Code. In the PCB panel, as you click on an entry in a list, a filter will be applied based on that entry. We’ll go over how differential pairs can hel. PCB Traces. 29 mm width traces to obtain 100 Ohms ZDiff while using 0. 2. By the way, I’d recommend using Saturn PCB Design Toolkit for impedance and other PCB calculations. 19mm) traces with 7. Let’s move onto another example. Overview. Contents. trace width: 0. Transferring the Differential Pairs to the PCB Editor from Schematics. This calculator finds both odd and even transmission line impedance. Earlier versions of the PCB editor included a simple impedance calculator, with limited support for unusual board structures. In order to maintain the impedance, I would like to use a power plane as reference beneath the signals, instead of the GND plane, as it provides better dimensions for routing (width and spacing) in the PCB toolkit calculator. 331 1 2 5. 035 ohms; single ended impedance: 45. Re: Calculating Differential Impedance for USB Differential Pair. There is a slightly different, but tightly coupled question here with this impedance calculator: "stripline differential impedance": Stripline here seems to be placed in some inside layer. It could result 5 Ohm resistance. Impedance and PCB Stacking The trace impedance is affected by many factors such as the width of the trace, th e thickness of the copper, the PCB material, the PCB stacking specification, and the spacing between the differential pairs. KiCad has a built-in impedance calculator!The two traces comprising a differential pair, when routed close together, share a certain amount of cross-coupling. This note describes some of the practical difficulties you'll sometimes run into when testing a controlled impedance PCB. It's true that generally the impedance value is determined by the following parameters; trace layer (microstrip or stripline), trace width, distance. frequency capabilities. trace width: 0. ) You need a ground plane right below the impedance-controlled pair. Bog standard FR4, the type used as standard by PCB manufacturers is not really up to the task of Gen3 PCIe. 5 mm = 4. Mutual inductance and capacitance exist between the two traces in a differential pair. net Forum. I used the KiCAD PCB calculator, asked the PCB manufacturer about the tangent loss (0. MX6 Design recommendations about 100 Ohms for differential pair is quite reasonable for FlexCAN. The odd mode impedance is the impedance of one transmission line when the pair is driven differentially. Coaxial Line Impedance. A PCB's trace impedance depends on its geometry, core and prepreg material, and layers. Uncoated Microstrip Differential Pair Impedance Calculator . 8). g. thanks to 6 layers I am now pretty confident that I can place all diff pairs on top and bottom layers, directly above the ground planes. The latter for embedded dual stripline layers only. These impedances depend in first approximation on the following PCB parameters. Some calculators will allow you to calculate trace impedance in a number of geometries, e. The impedance calculator determines the signal properties and clearances (first image), use that clearance in the via shielding Distance setting. Question #1: How to determine the required spacing between length-matched signals or differential pairs and the adjacent layers? If you are length matching that implies that the interface is probably fast enough to require controlled impedance. The visual result (in the design editor window) of the cumulative filter is determined by the highlighting methods enabled (Mask/Dim/Normal, Select, Zoom). Single-ended and differential pair routing guidelines impedance will have defined geometry to ensure impedance goals are met.