36 mm substrate, has an impedance to ground, unbalanced, of about 49 ohms. The characteristic impedance is generally defined to. The calculator is available in the Electrical Domain in Constraint Manager, from the The Smith Chart graphically maps S11=reflection coefficient= (ZL-Z0)/ (ZL+Z0) to Load Impedance (ZL), normalized to Z0 (source impedance = center of chart). The JLCPCB Impedance Calculator computes track width values and recommended stack-ups from user-input values of board thickness, copper weight, layer, target impedance, conductor spacing. At MADPCB, we are capable of calculating and control the impedance of rigid PCBs, flexible circuits and rigid-flex PCBs. But I am not able to match this impedance. Edge Coupled Stripline Impedance Calculator. This makes the problem of determining impedance much more complex, and building an initial lossless model requires a larger set of formulas from Wadell. 1. 22 mm; trace distance: 0. The HIGH level is brought up to a logic level (5 V, 3. In terms of how these calculators work, the impedance of a transmission line in a PCB can be calculated in four ways: Use the R, L, C, G parameters from the Telegrapher’s equations to calculate the impedance of the transmission line. As also noted in the picture, the subsequent calculations are on the: [2] top-layer single-end impedance; [3] top-layer differential impedance; [4] inner-layer differential impedance. ZL =. PCB Thickness is 1. 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. Copper thickness (t) = 18 micron. Development Kits. If you read many PCB design guidelines, particularly on parallel protocols and differential pair routing, you’ll see many mentions of trace length matching. How is Microstrip Impedance calculated?When you are creating your schematic, you must use one of the following suffixes when naming your differential pair nets: +/- (e. If you have placed Differential Pair directives on nets in the schematic, the default project options settings will result in the differential pairs members being created on the PCB. 0. PCB Assembly Quotes. 004” line. The calculator shows 90 ohms can be achieved using. Grounded Differential Coplanar Wave Guide. 3 V, etc. The ICD Stackup Planner calculates characteristic impedance plus edge coupled and broadside coupled differential impedance. Implementation of these guidelines can help designers maximize the performance of the. To achieve this, you may have to put small sections of trace tuning into the shorter line to equalize them. • As shown in Figure 1, traces should be 100-Ω(±5%) differential impedance of differential microstrip or differential stripline. Changed how the wire gauge calculator works, added max amps in air. Use 3. With PCBWay impedance calculator, you can calculate the approximate impedance of your PCB / high frequency circuit board. pairs for aciving 85 Ohm diff. First of all, we need to clarify the concept of characteristic impedance. Once you know the characteristic impedance, the differential. One question that is important in terms of signal integrity and manufacturability is how big the antipad in a PCB should be. To use this tool, enter the values for. I checked out TNT, but couldn't seem to be able to do the same with that either. Even mode impedance for commonly-driven transmission lines . The designer needs to create a stackup for the board and then calculate the trace values for differential pairs and single-ended nets. 5; w, t, s, h > 0;Made in Europe. Such a microstrip is constructed with two traces referenced to the same reference plane with a dielectric material between them. (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. With the Multi-CB impedance calculator, you can calculate the approximate impedance dimensioning of your PCB / high frequency circuit board. png . 3mm, as shown below: This increases the impedance slightly to 91. I used Saturn PCB design to calculate width and spacing between conductors. 25mm trace. D+ and D-) _P/_N (e. 0055” spacing. Coplanar Waveguide Analysis/Synthesis Calculator. 1. I used a calculator embedded in Saturn PCB and an online calculator on JLCPCB and PCBWay web side. , PCIe Gen 2 and Gen 3) also use a different value for differential pair. Saturn PCB Design Toolkit Differential Pair Impedance Calculator. 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. 2. 5. The differential impedance of MIPI tracks should be 100 Ohms, not 90 (USB requires 90). 1<W/H<3. ALTIUM DESIGNER For better impedance control, use PCB. Advertisement Board thickness (h) = 50 micron. This will give us the appropriate trace width and trace separation for the desired differential impedance. 1mm (3. 1 to 2. At some point the amplitude will stay constant. 0 and 0. It is only equal to double the characteristic impedance in certain cases. The vias on these differential pairs have their own impedance, which can create signal integrity problems on long interconnects. CAN bus layout design. W W = trace width. PCB Coplanar Waveguide Calculator RF PCBs can be complex boards that need careful interconnect design and layout. 1. 1kOhm, 1% tolerance: Brown Black Black Brown Brown. Suggested typical numbers for LVDS PCB using microstrip are, t = 1. In the first case, assuming edge coupled traces on (or in) a PWB, each trace couples much more strongly to the ground plane than it does to. 159 OS X 10_15_7 EasyEDA. Si TRC – Track Resistance Calculator calculates DC. 08-07-2018 02:42 AM. Cross-section geometry of a stripline trace. Design Parameters. Follow the 8W spacing for differential clocks (or explore other rules) Even greater spacing is needed for high-speed differential signals. Distance between pairs should be (traces on top layer = microstrip) 4 times the layer. Using this calculator, I found 100 Ohms by giving 9 mils of track width, 5 mils of track separation, 8 mils of dielectric (prepregs usually have a dielectric constant of 3. Updated formulas for all of the differential pair impedance models. 6 mm. Once the option is active, click on the shortest trace and move the mouse. In the image below, I am comparing differential vias with merged. 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. Eq. T1: Thickness of the trace. Technical Consultant Zach Peterson explores a viewer question surrounding Coplanar Routing, specifically how to route on a single-layer board. Board. 0037” line/0. > There are a lot of impedance calculators on the web but none seem to match each other. 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. 9. 34, 40, and 48 Ohms single-ended impedance are common, and each of these will have a specific corresponding differential pair impedance. 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. 1,481. $egingroup$ Note that it is possible to get 'free' impedance test coupons (the PCB fabricator will charge you for them). Low-voltage differential signaling (LVDS) is codified in the TIA/EIA-644 standard and is a serial signaling protocol. Some calculators will allow you to calculate trace impedance in a number of geometries, e. Altium Designer’s differential line impedance calculator will set up your impedance-controlled differential pair routing widths for you. I did my research on what the differential impedance is and how should I approach it. In the case where you are routing differential pairs, then the potential between the two pairs will always be opposing (i. To calculate the impedance, I use Saturn PCB impedance calculator software, Inc - PCB Toolkit V8. A differential stripline pair refers to two traces located between two reference plane layers, which are routed as a differential pair. 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. Propagation delay (t pd) in PCBs is the time taken by a signal to travel through a unit length of a transmission line . 127mm, or 127 μm for the calculator’s purposes. 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. A mistake was made when designing a set of mother and daughter PCBs, resulting the daughter board to have its LVDS pairs at ~100Ω differential impedance, while the motherboard ~90Ω. Differential Pair Impedance Calculator Calculates the differential pair impedance of a balanced line. These parameters include:This is eight layer stackup. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. This is the same reason we have to consider spacing between traces in differential pairs: the two conductors interact with each other to determine the odd-mode (and differential) impedance. Similar notes exist for other devices but USB is the one I'm most interested in. Capacitance – the impedance calculator uses the Impedance value to calculate the capacitance per unit length. 120 Ohm Differential Pair: 0. (1+ρ) (1-ρ) With most of today's TDR-capable instruments, such as the Tektronix sampling oscilloscope, TDR measurements can be displayed with units of volts, ohms, or ρ (rho) on the vertical magnitude scale. This 8W rule also applies to ground planes on the same layer. Using the KiCad Impedance Calculator. There are many demands placed on PCB stackup design. External Copper Thickness: Copper weight for the top and bottom layers. Both LM and CM converge to zero as spacing goes to infinity. Right-click and choose Change from the pop-up menu. The surface finish is neglected. 5. Those pairs connect via a dedicated FFC cable. Rs =. PCB Impedance and Capacitance Calculator: Asymmetric Differential Stripline. PCB DESIGN TOOL Impedance Calculator TRY TOOL . But it lacks the differential impedance (impedance between these two tracks). PTN33xx and CBTL061xx I/O impedance is targeted at 50 Ω single-ended and 100 Ω differential. 071 ohms; All About Circuits. While there are a number of online calculators that calculate the characteristic impedance from the input geometry, they are all based on approximations. They are very simple to read, and the values in. And this leads to our third rule: The separation between the two traces (of the differential pair) must remain constant over the entire length. The USB interface is a differential signal, so it requires a medium with defined differential impedance, to prevent signal reflections at discontinuities. The DC resistance is determined by the trace's conductivity and the cross-sectional area. The targeted impedance for diff pair is 100 ohms, which is dependent on the width/space between conductors and hight to the reference plane. With t = 35 um (typical for copper with plating on a pcb), Z odd drops to 44 ohms, according to LineCalc. The guides says spacing under 0. This video explains the most common layout topics for USB signals: impedance, trace length and matching, and printed circuit board (PCB) stack-up. Use several of them and compare. According to this guidelines, the differential pair (DP and DM signals of the USB) must have 90 ohm impedance to each other. The via transitions start to really matter above 5 GHz. It seems I could largely do without any impedance matching considerations, given what the trace lengths are. Differential Stripline Impedance Calculator. 5mm pitch has about 100 ohm differential impedance in the configuration where a differential data pair wires are between ground. Tech Consultant Zach Peterson di. Let’s move onto another example. THESE FORMULAS ARE APPROXIMATIONS! They should not be used when a high degree of accuracy is required. best to use a stackup calculator to provide quick ‘what if’ analysis of the possibilities. This calculator is designed to calculate the characteristic impedance of an edge-coupled microstrip. The JLCPCB results are more reliable than (some of) the simple formula-based approaches. Now, let us see the routing of the differential pair. It's important to note that the TIA/EIA-644 does not define. 4. 254mm. When you are creating your schematic, you must use one of the following suffixes when naming your differential pair nets: +/- (e. 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. A twisted-pair cable is simply two wires that are twisted together so as to reduce radiated EMI (electromagnetic interference) and mitigate the effects of received EMI. KiCad has a built-in impedance calculator!$egingroup$ To avoid crosstalk from neigbouring signals - including its own, you should apply the 3W rule of thumb - traces should be at least 3 times their width apart. I believe the 100-ohm differential equates to 50-ohm single ended because you can think of the two 100-ohm impedances as being in parallel resulting in an effective 50-ohm single-ended equivalence. Right-click and choose Change from the pop-up menu. Fig 1 Typical Pi termination for a coupled line pair. 15 mm spacing. 2Gbps 100R differential impedance, while the other is only 3Mbps, with much more tolerance on the impedance. 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. ) and the LOW level is defined as zero. H 1 H 1 = subtrate height 1. net Forum. In a previous article, we have seen how to route a differential pair signal. 1. They will give very similar answers. Enter the relative permitivity, width of the trace, the ground plane spacing, and the substrate thickness to calculate the characteristic impedance. 6mm 4 layer PCB, 1oz outer copper, 0. Geometric Parameter Definitions: Impedance calculation Broadside coupled stripline impedances (Z 0,odd , Z 0,even , Z 0,diff and Z 0,common ) shall be calculated as specified in previous paragraph. PCB impedance calculator – Single ended / Differential pair PCB manufacturer normally provides information about PCB stackup and track geometry. Yet I got a ZDiff CPW with ground capable calculator: Differential surface coplanar waveguide with ground calculations: *0. The amplitude of this crosstalk is what this tool calculates. This interactive controlled impedance routing greatly simplifies the task of designing a controlled impedance PCB. 1. In case your board only routes differential pairs between two connectors, you may not even have ground connected via cable shield to connector metal frame. 6mm thick. The default units for all given values, except the subtrate. AC coupling capacitors can be positioned anywhere throughout the differential pair’s length. Remember, the lower the impedance the greater the current drain, the higher the. PCB Design Quotes. The termination resistors on a cable should match the nominal impedance of the cable. Ask the board manufacturer for the values. Hello , I am designing a PCB that is featuring USB , I know that the USB traces diff impedance should be 90 ohms. If the goal is to adjust the characteristic impedance, then you can likely do it by changing both width and spacing (keeping center-to-center the same) just as well as by changing the width without changing the spacing. Note: The results are only for approximation and rough estimation, the final values and the. Differential pairs are becoming common place in high speed design reducing. Microstrip Impedance Calculator. PCB Trace Impedance Calculator Calculates the characteristic impedance and per-unit-length parameters of typical printed circuit board trace geometries. By understanding the microstrip transmission line, designers can. ZO *. Take account, the internal used formulas sometimes don't equal on Conductor Impedance tab and on Differential pairs tab (e. Difficulty in achieving 100 differential impedance accurately In order to have maximum coupling of the magnetic field lines, the space between two conductors of a differential pa ir should be kept to a minimum. Note: Units do not matter for this calculation as long as they are consistent. 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. At the receiver, the signal is recovered by taking the difference between the signal levels on. Several Web sites such as the examples listed below contain additional reference information. 3. e. Here it is already defined in the schematic that this is D+ and D-. Let’s discuss the need for impedance. Unfortunately, TxLine doesn't do coplanar waveguide for differential traces. High speed PCBs and signaling standards almost entirely use differential pairs with precise impedance. The 5S rule states that the spacing between two lines in a differential pair should be a factor 5 larger than the width of each trace in the pair. The trace separation is varied from 1. As most designers know, the impedance control in FR4 PCBs and PTFE PCBs are easy since the surface are almost absolutely flat, and there are many impedance calculating tools for choice. The factors that influence differential pair via impedance will affect the input impedance seen at the vias. 72 mil. USB traces must be 90 Ohms differential. Home. There are some signal integrity issues with de-skewing in traces: Impedance. Because the traces are together on the same layer (plane) I'm not sure how "coplanar". But I am afraid that, even an continuous power plane will not provide a proper reference for those Eth differential pairs. The default units for all given values, except the. Learn how to configure, define, and use your design’s impedance requirements for single-sided and differential on each layer, with Altium Designer’s Layer St. For example, a single 0. Grounded Differential Coplanar Wave Guide. Using the KiCad Impedance Calculator. When you are creating your schematic, you must use one of the following suffixes when naming your differential pair nets: +/- (e. Impedance calculators will help you to determine your line width and layer configurations while board layer stackup editors will help you to plug in the correct PCB materials and widths. PCB Stackup Impedance Calculator Calculates the characteristic impedance per unit length parameters of typical Some of the common Dielectrics & their values: Relative. Saturn PCB - Toolkit for Impedance Calculation. Fabricators give trace impedance tables as guides to designers that need to implement controlled impedance in their PCBs. 965 mm. For better impedance control, use PCB design software you can trust. For example, with a thickness of 0. g. 3. Value of Zo calculated by impedance calculator is not relevant here. This form of microstrip is composed of two traces. 81. 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. 5. PCB impedance calc and clearance. For sample: 45-46 Ohm single end traces impedance can be used in diff. arrow-right Download and install the Analog Engineer's Calculator. Signal Management. • A single differential pair should be routed as close together as possible. I've seen from several. For a differential pair, the available layers, the Preferred Width and the Preferred Gap are controlled by the selected profile. Eurocircuits’ PCB DEFINED IMPEDANCE pool is a fast turnaround solution for PCB’s with a specific impedance requirements for certain tracks. 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. 6mm pcb thickness ) with 8 mil trace width, 8 mil trace spacing , 1. The Differential Pair Impedance Calculator is a specialized tool used in electrical engineering and signal integrity analysis to determine the characteristic impedance of a differential pair of transmission lines. For a Dk = 4. Embedded Microstrip Trace. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. For differential signals on the top layer, I have 100 ohm impedance for trace width 5 mil and gap 5. 331 1 2 5. 50 to 60 Ω is a common target impedance used in many designs, and for differential pairs, 90 Ω or 100 Ω differential impedance is common. 25mm between the differential pair with a width of 0. When selecting trace geometry, priority should be given to matching the differential impedance over the single ended impedance. Also, be aware, 90 ohms is the differential impedance, the characteristic or single ended impedance will be more than half (ie. zip (170k) AP117. For example, when two traces with Z =50 W are well separated (uncoupled), the differential impedance between them should be precisely Z DIFF = 2. Twisted pairs are used with balanced signals. If T R = 1nS. 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. To have designs be robust from PCB manufacturing errors and defects design the traces impedance be as close to the recommended value. 5 to 4. To access the differential calculator, in the Primary Gap, Neck Gap, or +/- Tolerance cells, do the following steps: 4. While every trace has an impedance, we don't care about the trace reactance if the trace is only carrying DC current. High-speed designs carry a requirement for controlled impedance, crosstalk control, and the need for interplane capacitance. 6mm) That should give the traces around 90 Ohms differential impedance according to the PDF, but when I try to input it to my impedance calculator (Saturn PCB toolkit V7. NEW Methodical Method to Hardware & PCB Design - you can calculate single-ended impedance. Zachariah Peterson | Created: November 22, 2021 | Updated: June 25, 2023 Table of Contents Differential Impedance Defined Formulas for Differential Impedance Should You Use Characteristic or. Quote Now . 68 mils. 1. One should note that some routing and computer architecture standards (i. These features become essential if you generally work on high-speed designs. Altium Designer makes it easy to calculate geometry when you need to calculate impedance for differential pairs. If the track thickness and gap remain the same throughout the cross section of the PCB then it is recommended that the differential pair beI'm unsure if the reference plane would be the GND and the PWR layers. g. 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. 94 mil) is nominal thickness of 3313 prepreg. Grounded Differential Coplanar Wave Guide. Learn more about determining microstrip trace impedance; Learn more about determining symmetric stripline trace impedance; The fastest way to determine impedance is in PCB design software that. 5 and I took 3. 2. 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. A PCB impedance table will provide the trace width required to have a target impedance value on a standard stackup. Since it is always important that the trace impedance remain constant over the entire length, this means that the coupling must remain constant over the entire length. 4mils = 0. Note: valid for (w/h) from 0. Step 1 Calculate singled ended impedance for each: Use "impedance + trace space" from top drop down box: Set Z=50R, click single ened, gives a result of track. I am routing LVDS pair on a flex board. or Differential Pairs Routing design rule. 0. Complete the routing of a PCB design can be one of the most demanding PCB-related tasks. Crosstalk Area. Note that the driver output impedance may be configurable among various values. PCB Impedance and Capacitance Calculator: Asymmetric Stripline. SET2SEIL. A pair of lines can be modeled as follows: Differential pair line. 9. To automatically select all traces that belong to a specific impedance profile, you can select Nets in the the PCB Panel and click the appropriate net class. 5 mil (0. Here, we have set the differential tracks and spacing as 8 mils. or Differential Pairs Routing design rule. Inductance – the impedance calculator uses the Impedance value to calculate the inductance per unit length. Using the KiCad Impedance Calculator. We recommend the software from Polar Instruments if you want to get exact impedance calculation. (Sorry guys, I live and I have grown up in a metric world ) With these values, Saturn PCB's off-line calculator gives 57 Ohm differential impedance. I tried to use the tool “PCB calculator” to determine the size of mi USB tracks. Additionally, it only takes into account single-ended structures (not. Microstrip Impedance Calculator. /. Differential Impedance in Constraint Manager Advanced Constraints can be used to view the Differential Impedance in Constraint Manager. In other words, if you are designing to hit a differential impedance target (such as. 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. A PCB impedance table will provide the trace width required to have a target impedance value on a standard stackup. 6 ohms and Z even = 110 ohms for your geometry, very close to your result. 36 mm substrate, has an impedance to ground, unbalanced, of about 49 ohms. We’ll go over how differential pairs can hel. 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. common impedance: 19. Differential pair routing information; High-speed routing information such as constraints for trace lengths, matched lengths, topologies, and controlled impedance lines; Don’t be afraid to add as much information as possible to the schematic to promote design intent in the board layout. I am designing a flexible PCB to carry two types of differential signals. dear friends I want to route 100 ohm differential pairs of LAN on two layer pcb ( 1. Keep the spacing between the pair consistent. See moreCalculate the impedance of PCB traces quickly and easilly using DigiKey's Trace Impedance Calculator. Giving the PCB house the data can take one of two forms. In the PCB panel, as you click on an entry in a list, a filter will be applied based on that entry. Terminate far end of the pair with 90 Ohms resistor (it is odd mode. This will create the differential pair. PCB impedance control is an important design constraint when working on high-frequency circuits. Only one trace width or pair geometry can meet a particular target impedance per layer. Fringing Electromagnetic Fields Coupled Fields Microstrip StriplineThe PCB design tools in Allegro include an impedance calculator that will help you size your traces so that they have defined characteristic impedance. 8mm PCB instead of 1. Coaxial Line Impedance. This calculator requires symmetry in the trace widths and location between plane. So, I am trying to figure out how to use Kicad’s PCB Calculator for “Coupled Microstrip Lines”: I’m unsure about what a couple of the parameters mean and can’t find an explanation in the docs (it just. 0175mm of Copper (1/2 oz), gives me a best estimate of 9mil trace, 4mil space for a 90R differential microstrip impedance. Differential Protocol: Select the desired protocol from the dropdown list, this list will autofill the Target ZDiff edit box. Once the option is active, click on the shortest trace and move the mouse. Thus a "differential pair" any long distance apart will have an impedance of 98 ohms, without any coupling between the lines, i. The impedance calculator determines the signal properties and clearances (first image), use that clearance in the via shielding Distance setting. Differential Protocol: Select the desired protocol from the dropdown list, this list will autofill the Target ZDiff edit box. The two most common impedances. 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. 9dB) • Minimize differential return loss (typical -12dB) • Minimize mode conversion –Intra-pair skew matching (50 ps of t RX HBR3)PCB trace length matching is exactly as its name suggests: you are matching the lengths of two or more PCB traces as they are routed across a board. PCB Structures / Discrete Structures / Signal Management. That option operates on a single trace. One of the features of this type of microstrip is the coupling between lines. The same applies to differential pairs. Sierra. You can see for example, Matthew K. Altium Designer makes it easy to calculate geometry when you need to calculate impedance for differential pairs. GDCPW is known for its balanced configuration, which helps reduce common-mode noise and interference in. Make sure you use an accurate tool like this. 1<S/H<3. Other common impedance types include odd mode, common mode, and even mode. 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. 16 mil. Phone: +44 (0)1425 489 111 / +49 (0) 8104 628 0. KiCad has a built-in impedance calculator!Signals on an FR4 PCB travel at approx half the speed of light, so you'd want to make your longest trace no more than 44 mm longer than the shortest trace. Best-in-Class PCB Fabrication, Assembly, & Components. Calculates the characteristic impedance and per-unit-length parameters. While commonly constructed using. . eu. Ideally you'd need 2 lines with Zo =45 Ohms. The characteristic impedance (Z o) of coplanar waveguide with ground or microstrip lines with signal side ground plane can be. 3 can then be used to design a PCB trace to match the impedance required by the circuit.