This calculator is designed to find the characteristic impedance of an asymmetric stripline - a flat conductor between two ground planes. Most often, the only specified requirement of a differential pair is its differential impedance. The amplitude increases as the coupling length increases up to a point. Let’s start new project together!The edge couple differential symmetric stripline transmission line is a common technique for routing differential traces. 0 and (t/h) less than 0. Differential impedance. Include both the pcb dielectric thickness as well as the wire insulation in the height calculation. The coaxial cable, along with the balanced two-wire, is the most common type of transmission line used in RF communications. Use the following guidelines. Following is the formula for differential impedance for a Stripline. Classes for 50 and 100-ohm traces. For a given differential impedance specification , a change in spacing and substrate thickness forces a change in the trace width in order to maintain the same odd-mode impedance value. 5 mil as the thickness of 3313 prepreg when the controlled impedance tracks are on top/bottom, use 5. 77 mm gave me a differential impedance very close to 90 Ω. This is more than the to times trace width which is recommended (also read as close as possibly). pair impedance with predifined traces’ gap. 5 – Calculation of Differential Impedance using online Calculator Notice that in the above case we get 100 Ohms for 18 mils separation between the + and – traces and 10 mils separation from the ground trace. Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. Speedstack is the stackup design tool of choice for professional PCB Designers fabricators and brokers who have a requirement to document and design stackups drill plans and material requirements complete with high. Dielectric thickness may vary, but at the moment I have 4mils. Atlas Si for VNA – Insertion loss test system – Delta-L 4. To obtain a particular value of differential impedance, the two signal tracks are usually assumed to have the same cross-section — the balanced track case, used in most impedance calculation software. Edge Coupled Microstrip Impedance Calculator. This is assuming that you have a Design Rule in place which links the impedance profile to a. You can use all the calculators you want if you don't know the exact board make up they're using; they should be able to help you. The source for formulas used in this calculator (except where otherwise noted) is the Design Guide for Electronic Packaging Utilizing High-Speed Techniques (4th Working Draft, IPC-2251, February 2001. The differential impedance is always smaller than twice the single. In principle, you can calculate the inductance of a trace with a 3D field solver utility, but this is not the norm in transmission line design. To update trace width, select the traces of interest and use the "Route > Retrace Selected" command. Given the defaults (1. Most popular calculators don’t even have a box height parameter. Disc Air Capacitor Calculator; Impedance Calculator : XL, XC; Inductors, Transformers. The calculator shows 90 ohms can be achieved using. There have been trace routing tools available for a long time that help with differential pair routing, and designers have had access to impedance calculators to determine their trace widths. Controlled Impedance; PrePreg Chart. You can use a trace impedance calculator for stripline and just make the H (height above the ground plane) very large. 6 ohms and Z even = 110 ohms for your geometry, very close to your result. infinite mutual. They will often lead you astray, unless you only have one trace on your board, or surrounding traces are a centimeter away. Re: Calculating Differential Impedance for USB Differential Pair. By inputting the known values. 50 - 55 ohms). Insertion Loss. Zo (diff) is calculated to be 244 ohms, so dividing by two yields a value of 122 ohms for the semi-coplanar structure. **Note: Like our stripline impedance calculator, all of our RF calculators allow SI prefix input. 331 1 2 5. I've used 7 mil trace width with 5 mil spacing, top and bottom layers (35um copper) are 0. Let's match the impedance of the same signal since differential pair routing is completed when the impedance is matched properly. The differential skew is adjusted with a tiny blip on one line towards the bottom of this image. If you need to use differential pairs, you simply define traces in each layer as differential pairs and the impedance calculator will determine the correct spacing between traces. Using this data in a frequency-dependent solver, the impedance of the trace looks like this (note the additional 1. Single ended impedance is the trace impedance with reference to ground. 30967mm) is slightly larger the size of the smallest pad (0. Single Ended Impedance Ω. Bus line impedance (Z Bus) Differential Mode line impedance (Z Differential) Common Mode line impedance (Z Common) The Single Line impedance is based on the inductance L and capacitance C per unit length of the trace and can be calculated by the following formula: Below there a few examples where the single line impedance is of interest: Coplanar Waveguide Calculator. 6mm spacing with a trace width of 0. Since PIe edge connector’s character impedance is 85Ω, the traces between the connector and I should be 85Ω -- the rest is usually set to 100Ω. you need to get all the details from Manufacturer. Single-ended signals are fairly straightforward. Press the Analyze button to calculate the electrical parameters. Enter the relative permitivity, width of the trace, the ground plane spacing, and the substrate thickness to calculate the characteristic impedance. Wavelength/10 is the max trace length before you need to worry about impedance control So if you keep your traces under 15mm in length, then it doesn't matter. 1 Effective Permittivity and Characteristic Impedance of CPW. • Keep single-ended signals away from differential traces – distances should be at least at least 2x the trace width. EasyEDA directly supports controlled impedance designs for 4 and 6 layer PCBs only. KB: Prevent multiple license seats being used on one installation instance. To avoid microstrip modes, have h >> (w+2g) and extend component side ground away from the trace by > (w+2g). 6mm spacing with a trace width of 0. Calculate the impedance gradient and the reflection coefficient gradient. Z 0 = Single Ended Impedance. Figure 8. Tuning for your traces to the desired impedance value occurs by adjusting trace width and distance from the reference plane. Chrome 92. If the negative trace in a differential signal is a higher voltage than the positive trace, then you have a high logic state, and if it’s the other way around, then you have a low logic state. 8. The Differential microstrip impedance calculator is used to compute the differential (Zd) and single-ended impedance (Zo) of an edge-coupled microstrip line just by entering the width, separation and thickness of the. Copper thickness (t) = 18 micron. The PCB Impedance Calculator in Altium Designer. This calculator requires symmetry in the trace widths and location between plane layers. 0. I would like to increase the width of my traces whilst maintaining the same ~50 Ohm nominal characteristic impedance of my line. This note describes some. Differential Pair Impedance Calculator Our impedance calculator features two main types of impedance models, single-ended and differential, within each trace structure. 16 mm. The bus impedance of the RS485 is approximately 100-120 Ohms differential and control trace impedance as ~50 Ohms. Just enter the given values for trace thickness, substrate heights, trace width and subtrate dielectric in the calculator above and press the "calculate" button. It is admittedly small, but it is non-zero. The top surface and the sides of the traces are exposed to air and are referenced to a power or ground plane. • Trace width of any un-coupled section of a differential trace greater than 100-mils, should be increased to maintain target impedanceLength-tuning structures and their effects on impedance. To calculate the impedance, I use Saturn PCB impedance calculator software, Inc - PCB Toolkit V8. This calculator. 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. The microstrip impedance represents the characteristic impedance of the microstrip line, which is the uniform impedance provided by the uniform cross-sectional dimensions along the microstrip (flat copper conductor) length; to prevent signal reflection. 2 of the Microstrip Calculator, h=H1 and b=H2-H1. I use FR-4, so H=1. While discontinuities might be unavoidable, they should be lumped together to keep their area small. 100 Ohm diferential impedance microstrip PCB traces geometries in. The guides says spacing under 0. Unit: Options are mm, mil, μm,. The calculator shows 90 ohms can be achieved using. 6mm thick. I suggest interested parties find an online trace impedance calculator and play around with some geometries. D = Separation between the differential traces. So, the trace width and distance to adjacent reference plane is determined by the desired. 3. Stripline. Remember to maintain 100 Ω differential impedance. Impedance captures the real and complex. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion, copper roughness, phase shift, etc. H= Distance between signal trace and ground plane. Differential Stripline Impedance Calculator. 0 specs requires a differential impedance of 90 Ohms and a common mode impedance of 30 Ohms (with some tolerance). Microstrip Differential Impedance Formula. It incorporates many features that PCB designers and engineers are in regular need. Use several of them and compare. Edge Coupled Stripline Impedance Calculator. Impedance examples 4 layers 1. 02 ; Height of substrate (thickness): 1. Microstrip Trace Impedance Calculator; Stripline Trace Impedance Calculator; Differential Trace Microstrip Impedance Calculator; Differential Trace Stripline Impedance Calculator; The. The closer you place the pairs together, the differential impedance gets smaller because LM and CM get larger. The microstrip is a very simple yet useful way to create a transmission line with a PCB. The impedance calculator determines the signal properties and clearances (first image), use that clearance in the via shielding. The calculator below uses Wadell’s. 15 mm. The following impedance calculators are. Example Problem: Use the following variables as an example problem to. The differential via design shown in Figure 2 was built and tested. Dielectric constant = 3. The impedance calculator in the Allegro stack-up editor uses a static 2D field solver by default (bem2d). $egingroup$ So basically your answer shows that the JLCPCB impedance calculator results are generally in the same ballpark as the proven field simulators. 4. This constitutes an impedance discontinuity causing reflections and EMI. Differential Microstrip Impedance Calculator Note: valid for (w/h) from 0. The following equations can be used to calculate the differential impedance of the board. Board thickness (h) = 50 micron. Matching the differential trace length and keeping the distances properly, this calculator is used to calculate the characteristic impedance of an edge coupled microstrip. Equation 2. 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. x allows an easy way to make differential pairs and keep control of the trace length, thus the phase or skew between the traces. To find what a given trace width will have a single ended or differential impedance, we can use a built in calculator from Allegro. There are four different types of impedance used in characterizing differential trace impedances. 2. How to calculate track widths and layout controlled impedance traces (e. signals. 3mm of the microcontroller), therefore i rounded the width to 0. 0mm (4L-02) When using our free Defined layer buildup 4L-02, you will reach the desired impedances e. To the extent that the differential impedance is less than 100 Ohms, it is due to mutual coupling. The characteristic impedance is given by: Eq. The amplitude of this crosstalk is what this tool calculates. There are four different types of impedance. when two coupled tracks are used to give a differential impedance. 2. 3mm, as shown below: This increases the impedance slightly to 91. The characteristic impedance of your microstrips is determined by the trace width for a given layer stackup. Note that Zdiff (differential impedance) is equal to 2 * Zodd, so a Zodd of 45 Ω gives us a Zdiff of 90 Ω. Calculate the Differential Microstrip Impedance of a transmission line based on the the distance between the strips, height of the substrate, trace thickness and dielectric constant of the substrate. Modeling approximation can be used to understand the impedance of the edge couple differential stripline transmission line. 2. To maximize signal integrity, proper routing techniques for differential signals are important for high-speed designs. To get the correct parameters, we have to use the specifications from our PCB house and the provided calculator. Single-Ended Impedance. AC Termination: AC Termination of a line results in the lowest power drain, but also requires two parts. The edge couple differential microstrip transmission line is a common technique for routing differential traces. Getting the Most Accurate Impedance Calculations. This transmission line calculator was. TheseIt always defaults to 10mil. 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. Calculates the characteristic impedance and per-unit-length parameters. , power and/or GND) constitutes a stripline layout. 48 e -0. 50 Ohms) for high-frequency signals. e. The required values are trace thickness, substrate heights, trace width, and subtrate dielectric in the calculator above and press the "calculate" button. Board Setup. But it's going to high, probably over 100 ohms. Asymmetric Stripline. This makes the problem of determining impedance much more complex, and building an initial lossless model requires a larger set of formulas. Mutual inductance and capacitance exist between the two traces in a differential pair. Standard 4-Layer Stackup. PCB stackup, signal integrity and controlled impedance: Signal integrity tools: Stackup design. To meet those requirements I used some online impedance calculators to estimate the required trace properties for a 2-layer FR4 PCB. . The test sample consists of a pair of differential traces at the top layer, followed by a differential via to the inner traces, then a second differential via connects to the BGA landing pads at the top layer again. (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. In other words, if you are designing to hit a differential impedance target. In fab notes, give the expected impedance (100ohm differential), the acceptable tolerance (often +/-10% or 20%), and which traces are. USB 2 e. 1 of the Microstrip Calculator using H2 in place of h, εr,eff can be computed as specified in Eq. 96D/H). This calculator is designed to calculate the characteristic impedance of a microstrip - a flat conductor suspended over a ground plane with a dielectric between them (see diagram below). Z0 = (60 / √εr) * ln ( (8h) / (w + s)) Where εr is the dielectric constant of the substrate material, h is the substrate height, w is the trace width, and s is the spacing between traces. Capacitance – the impedance calculator uses the Impedance value to calculate the capacitance per unit length. Unfortunately, TxLine doesn't do coplanar waveguide for differential traces. Following is the formula for differential impedance for a Microstrip. Different board materials, the dielectric layer thicknesses and constant (Dk), and the thickness of the metal traces all need to be part of the calculations. 0. 75 mm=30 mil). At the receiver, the signal is recovered by taking the difference between the signal levels on. The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a calculated impedance according to the IPC-2141 standard. Separation between the coupled differential trace pairs must be 1x. Altium Designer’s differential line impedance calculator will set up your impedance-controlled differential pair routing widths for you. See full list on resources. This is because communication flows both ways on the CAN bus. There are many demands placed on PCB stackup design. No, the single-ended impedance provided in differential line calculators does not matter. Stripline. There are many factors that go into calculating the width of an impedance controlled trace. Still, as you correctly analyzed it is much better to think of the individual lines in a differential pair as two length-matched single-ended lines, both with the half impedance. The USB 2. Differential impedance, Z diff, is the impedance between the two conductors. PCI Express: 90Ω ±15%: 50Ω ±15%: 2. 2 Ω impedance. A Trace Length Calculator for Differential Pairs and Nets. Introduction The edge couple differential microstrip transmission line is a common technique for routing differential traces. PCB Impedance-Calculation: Help with the dimensioning of the impedances of your circuit board. Impedance in your traces becomes a critical parameter to consider during stackup design for high-speed PCBs, but the. High-quality circuit boards as prototype and series at reasonable prices. Tuning for your traces to the desired impedance value occurs by adjusting trace width and distance from the reference plane. 5. when i use Saturn PCB design to match the differential impedance to 100ohms i get 0. 5. Need to consider this if the data rate is 5 Gbps and above. Calculating the Differential impedance is a two-step process, first Calculate the single ended impedance Zo and then use this value to calculate the differential. But I see that the EEWeb free tools don’t have. Use several of them and compare. The PCB trace width and the spacing to the grounded copper regions need to be designed to set the designed impedance to the. • Choose a suitable board stack-up that supports 75 Ωsingle-ended trace and 100 Ωcoupled differential characteristic impedance trace routing. Board Setup. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. Home;. I found that a W of 0. Includes information on how trace width is calculated. When a single trace is considered in isolation, its impedance will have a well-defined value. The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a calculated impedance according to the IPC-2141 standard. Every trace has capacitance between the trace and the return path of the signal on. Missing by 25 microns on a 100 micron trace throws off the alignment by 25%. In this worst-vase scenario, the via would. In reality, we don’t need to use that trace width due to the way the traces in differential pairs will couple to each other. You may wonder why it dips initially. 1 to 3. How to calculate differential impedance: Notes. The stripline impedance calculator provided below is useful for gaining an initial estimate of trace impedance for striplines. The track widths should. From this equation, calculate the real and imaginary components to. 25mm trace. 2mm from the ground plane below. A coplanar waveguide calculator will operate in one of two ways. The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a. They will trim the trace width based on their experience with their stackup, accordingly. The spacing between two traces in a differential pair should not be more than twice the width of the traces. In addition to characteristic impedance analysis, the signal integrity extension can perform equivalent circuit modeling of a particular trace or differential pair. You can use a trace impedance calculator for stripline and just make the H (height above the ground plane) very large. Figure 3. The efficiency of transmission of the embedded microstrip greatly depends on its characteristic impedance. The default units for all given values, except the subtrate dielectric, is in millimetres. differential amplifier 9. When the two lines are far apart (say, more than 3 or 4 trace widths), then the lines are weakly coupled and the individual line impedance is about 1/2 the pair. You simply need to select both ends of the pair to ensure the differential impedance remains consistent throughout the board. Differential Stripline Impedance Calculator. The idea here is to determine the spacing required for a given width with the goal of hitting a specific differential impedance value. Instant online PCB quote, get PCBs for only $2. 0 and (t/h) less than 0. Dial down these variables, calculate exactly what you’re impedance needs to be. Physical geometries of differential traces To calculate the trace geometries in Figure 5 for a 100 Ω differential impedance TMDS signal pair, the closed-form equations 1 – 6 can. But make sure you get the spacing between the diff pairs and their thickness (copper weight) correct. IPC 2141 Trace Impedance Calculator. Dielectric Constant, Ε r: Trace Width, w in mils : Trace separation, d in mils : Trace thickness, t in mils : Dielectric thickness, h in mils : OUTPUTS Characteristic impedance in Ohms : Differential microstrip impedance in Ohms : *Note: This calculator is valid for (W/h) in range from 0. 35mm gives 50Ω, far easier to use. Every trace has series inductance. The default units for all given values, except the subtrate. Voltage Divider Calculator 1 (Fixed) Voltage Divider Calculator 2 (Adjusteable) Capacitors. 8. The surface finish is neglected. The characteristic impedance (Z o) of coplanar waveguide with ground or microstrip lines with signal side ground plane can be. (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. Embedded Microstrip Trace. Hello! I'm trying to calculate the trace width for a differential pair (carrying MIPI CSI-2 signals), using JLC's impedance calculator. Differential Impedance is the impedance between two differential pair signal traces. This calculator finds both odd and even transmission line impedance. with the following layout parameters (width|space|width): Ohm. 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. Insertion Loss. Just enter the given values for trace thickness. Image Credit: Maxfield EEWeb - Stacking the traces calls for a tight layer to layer registration requirement. Using this calculator, I found 100 Ohms by giving 9 mils of track width, 5 mils of track separation, 8 mils of dielectric. 6mils. This calculator finds both odd and even transmission line impedance, including four different types of impedance used in characterizing differential trace impedances, for microwave antennas, couplers and filters applications. I would like to know how to calculate trace width and gap to route differential pair in this situation. That trace has an impedance,. This calculator can calculate the impedance and propagation delay of the embedded microstrip. Figure 13: There are single end trace impedance and distance between traces in the pair. you need to get trace widht and trace thickness,impedance value for your trace (single and Differential). 68 mils. pairs for aciving 85 Ohm diff. 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. 0. Since the op is using 1/2 oz copper this should be taken into account. We get a lot of questions about trace impedance and how to calculate the right trace size to hit a specific impedance in a manufacturable PCB. Create a differential trace with KiCad - Schematic. With PCBWay impedance calculator, you can calculate the approximate impedance of your PCB / high frequency circuit board. What we have on these differential traces is a taper section, which RF engineers often use to match impedances. The Layer Stack Manager's impedance calculator uses the Wideband Debye model, with a default frequency. Note 1: The impedance tolerance after manufacturing may be around +/-20% on outer layers and +/-10% on inner layers. Try TNT or TxLine. x. Select the box with the geometry that you would like to calculate. Given these design specifications, lab measurements of this standard differential via are correlated with HFSS simulation results to first calibrate th e simulation setup. 2. Figure 4. Reference layer. All the best. Instructions are below the calculator and don’t forget we can make and test your controlled impedance printed circuit boards too. Note that Zdiff (differential impedance) is equal to 2 * Zodd, so a Zodd of 45 Ω gives us a Zdiff of 90 Ω. Performing PCB trace length matching vs frequency correctly requires considering the entire bandwidth of a propagating signal on a trace. ALGEBRAIC EQUATIONS Single Track For the stripline of Figure 2 with a symmetrically centredIf your design has controlled impedance traces, you can use our built-in impedance calculator. 25mm, a trace width of 0. Going Forward with a Trace Impedance Calculator. The Si8000m assumes negligible insertion loss in the transmission line; should you wish to model insertion loss the Si9000e adds. This calculator is designed to calculate the characteristic impedance of a microstrip - a flat conductor suspended over a ground plane with a dielectric between them (see diagram below). Dual Stripline Trace. Now select the two nets that you want to declare differential. Use an impedance calculator to determine the trace width (W) and spacing (S) required for the specific board stack-up being used. Controlling trace width within a tolerance of +/- 10% is necessary for better impedance control. 0. 19mm) traces with 7. Note: valid for (w/h) from 0. Whether you’re an electronics enthusiast or a professional, this tool will. 5ohms and the fact that it’s nearly flat above about 800kHz). The ground plane helps. In this design there is a coplanar ground plane a controlled distance away from the trace that is close enough that it significantly affects the impedance of the trace. 03) it gives me almost 160 Ohm - and even if use 53mil conductor height or. View All Tools. This calculator allows you to add the impedance model and compute the desired trace geometry and spacing for a target impedance. 5. 2 Loss of CPW lines; 3. The characteristic impedance of your microstrips is determined by the trace width for a given layer stackup. While commonly constructed using printed circuit boards, this structure can also be built using other materials as long as there is a conductor separated from. When designing the trace configuration for your differential pairs, you are typically targeting 100 ohms differential. Press the Analyze button to calculate the electrical parameters. Several Web sites such as the examples listed below contain additional reference information. Figure 3 shows the respective p and T models used to calculate the differential impedance (Z diff). "Saturn PCB Toolkit" is also good for this. The board contains two inner layers of GND and a ground plane around the RF track: To decide the thickness of the RF track, I used an online calculator:. Based on Zo Equation Per: IPC-D-317A: Formula:The rules shown below are a rough approximation, and you should always check the approximation using an impedance calculator or field solver. don't change the any dielectrical contant. Create a differential trace with KiCad - Schematic. Modeling approximation can be used to understand the impedance of. com To use this tool, enter the values for trace thickness, substrate height, trace width, trace spacing and subtrate dielectric in the calculator above and press the "calculate" button. Take note that this assumes that the distance between the conductor and the planes is not the same for both reference planes; hence the asymmetric term. ZO *. For example, if you wish to input "25000000", just type "25M" instead. eu. How do cheap Raspberry CSI-2 cables get around differential impedance matching. Trace stubs must be avoided. SET2SEIL. However, Figure 23 shows that for the TCM1-83X+, additional capacitance at the balun input causes a small. 35mm gives 50Ω, far easier to use. Although JLCPCB can produce boards with 2 oz external copper, the calculator only supports 1 oz because (1) the wider tolerance of 2 oz traces hinders impedance control, and (2) most signal traces only carries small currents. Choose a calculator to tune your PCB design. There are single end trace impedance and distance between traces in the pair. KB: Route traces between flex and rigid regions. The termination resistor [R] is still selected to match the trace impedance [Z o], while the capacitor is selected by: X c = [3 * T r] / Z o. e. The length matching of these differential pairs is important because these two lines are time-dependent or. The differential impedance depends upon the D/H ratio. Several online tools can calculate the required trace width to carry rated current while keeping the trace temperature below a specified limit. Common-mode impedance occurs with the pair driven in parallel from a common-source. PCB Trace Impedance Calculator. In the special situation for which there is no coupling to ground, Differential impedance equals the Characteristic. Differential signaling will produce a voltage effect between the traces similar to odd-mode. KiCad 5. Make sure to follow below for efficient RS485. Board. The source for formulas used in this calculator (except where otherwise noted) is the Design Guide for Electronic Packaging Utilizing High-Speed Techniques (4th Working Draft, IPC-2251, February 2001. Distance between tracks (s) = 254 micron. To summarize, the common and differential. x. 25, but gives me nice trace from the module to the stub then to. 5mil clearance on a 63 mil board (1. Z diff = 2* Zo (1 - 0. Note the differential pairs above that look like a strand of intestine have a constant gap between the pairs. *The structure may propagate in 3 modes: coplanar waveguide, coupled slot lines and microstrip. 4. Figure 25. 1 mm trace spacing chosen in your design. If you keep the traces short, it will work even if the impedance is. 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. In both cases, you’ll need to enter your stackup information into the calculator to get accurate results. I have already some experience on single ended controlled impedance but this is my first. The differential impedance between the positive and negative trace of the transmission line is slightly less than twice the impedance of the single ended impedance. Note: Units do not matter for this calculation as long as they are consistent. If trace width is increased for the metal losses reduction, the single end impedance will be reduces. The net result is that trace impedance will suffer dynamic variation as random data signals propagate through the traces. Description. Ask the board manufacturer for the values.