The datasheet mentions that the LVSTL is tuneable, but what is the nominal differential and single ended impedance for these PCB traces? I have also checked the TN-53-06: LPDDR4/LPDDR4X Point-to-Point Design Guidelines from micron and it says this: Standard characteristic impedance (Z0) of no more than 50Ω, nominally, is. 6mm thick. 6. Look what happens to the impedance if we place a ground plane on the top layer that is close to our signal. Controlled impedance traces can minimize signal reflections and thereby reduce propagation delay. These people can illustrate their points very convincingly with parts specs and sig-nal timing diagrams. Differential signaling in flex circuits follows the design method of surface microstrip transmission lines. 2. 5 mil (2116 prepreg) or 8. Note 1: The impedance tolerance after manufacturing may be around +/-20% on outer layers and +/-10% on inner layers. Use the following guidelines. The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a. The more closely differential traces are routed together, the more equal any coupled noise will be on each trace, and the better will be the rejection of the noise in the circuit. TheseDifferential impedance Single-ended impedance; 1. Free Trace Line Impedance Calculators that utilize the #3 approach. The Smith Chart graphically maps S11=reflection coefficient= (ZL-Z0)/ (ZL+Z0) to Load Impedance (ZL), normalized to Z0 (source impedance = center of chart). There are many calculators available online, as well as built into your PCB design software. But to find a PCB routing system that calculates trace widths automatically factoring dielectric constants and the board layer stackup, and then. This will give us the appropriate trace width and trace separation for the desired differential impedance. Using an online calculator [4], a microstrip trace of 1oz, 120mil-wide copper on 0. Notes: 1) Calculation assumes traces are centered vertically. TheseIt always defaults to 10mil. 6mils. The closer you place the pairs together, the differential impedance gets smaller because LM and CM get larger. For high impedance, make the outer dieletric as thick as possible. This calculator. Given the defaults (1. Click on Setup -> Constraints > Electrical Constraints Set - > Differential Pair Value - > Calculator > If you put 10 in the Line Width, the calculator calculates the single ended as well as differential impedance. 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. A Trace Length Calculator for Differential Pairs and Nets. 2 Ω impedance. Impedance examples 4 layers 1. Creating and Configuring an Impedance Profile. One thing is for sure: When you are routing a high-speed PCB design you are going to be working with impedance-controlled routing and. 254mm. trace width and thickness, distance from other copper features, dielectric constant, and dielectric thickness or distance to reference plane of the board material all contribute to the impedance of a. They will give very similar. This note describes some. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. To find what a given trace width will have a single ended or differential impedance, we can use a built in calculator from Allegro. Microstrip and Stripline Differential Pair Dimensions For better coupling within a differential pair, make S < 2W, S < B, and D = 2S where: W width of a single trace in a differential pair S space between two traces of a differential pair D space between two adjacent differential pairs B thickness of the boardThe twisted pair helps create a more uniform inductance and capacitance per unit length of wire to ensure a constant impedance, by keeping the return path as close to the signal as possible. Calculates the characteristic impedance and per-unit-length parameters of typical printed circuit board trace geometries. You can use a trace impedance calculator for stripline and just make the H (height above the ground plane) very large. The stub length must. impedance to rise. KiCad 5. So, let’s finish this. 36 mm substrate, has an impedance to ground, unbalanced, of about 49 ohms. Calculates the current a conductor needs to raise its temperature over ambient per IPC-2152. Z diff = 2* Z o (1 - 0. Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. It is only equal to double the characteristic impedance in certain cases. 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. Calculate the trace parameters for controlled impedance: Determine trace thickness, height, and length along with the dielectric constant of the material. Yes, solder mask can lower the single line impedance by 1 - 2 ohms and the differential impedance by 3 - 4 ohms for thin traces. 1 Effective Permittivity and Characteristic Impedance of CPW. The impedance of a differential via pair cannot be treated with a single via impedance calculator unless the vias are spaced far apart. AC Termination: AC Termination of a line results in the lowest power drain, but also requires two parts. Here, we need to consider termination for the traces used in the above image, as well as the target impedance and skew limits between various traces. Ensuring impedance-controlled routing also requires knowledge of the substrate’s dielectric constant and your required trace width. 03) it gives me almost 160 Ohm - and even if use 53mil conductor height or. Just to give designers a starting point, take a look at these differential impedance calculators you can use to get an initial estimate of the differential. tween the two halves of a differential signal pair and still switch reliably. The calculator below uses Wadell’s. Use an online differential microstrip impedance calculator; Use an online differential stripline impedance calculator; Calculating Differential vs. A coplanar differential raises the diff impedance while lowering Zo with adjacent grounds so it needs a thinner height of dielectric. 5 Summary; Microstrip is the most popular medium for circuit design at frequencies ranging from several hundred megahertz to tens of gigahertz. When the termination resistor matches the track impedance, there will be no reflections. The tool provides two networks that will have the desired impedence at that frequency. High speed measurement tools. Note: valid for (w/h) from 0. Just enter the given values for trace thickness. All the best. 3mm of the microcontroller), therefore i rounded the width to 0. Differential impedance, Z diff, is the impedance between the two conductors. 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. 2H, the formula for the non-embedded. Dielectric thickness may vary, but at the moment I have 4mils. 3mm, as shown below: This increases the impedance slightly to 91. Si TRC – Track Resistance Calculator calculates DC. e. Differential Impedance of. Compatible with Flex PCBs and Turnkey PRO service. EEWeb offers a free online twisted pair impedance (transmission line) calculator. The calculator is available in the Electrical Domain in Constraint Manager, from theTrack and gap widths are of concern in controlled impedance, but unless your speaker and mic connections (I assume audio frequencies) are going a long way you should not have any particular requirement for controlled impedance. When a trace is carrying a DC current, then the resistance will determine how much power could be lost along that current path. Just enter the given values for trace thickness, substrate heights, trace width, and substrate dielectric. By inputting the known values. Differential Stripline Impedance Calculator. The microstrip is a very simple yet useful way to create a transmission line with a PCB. 5 mil (0. . But these people miss the point. The differential impedance of MIPI tracks should be 100 Ohms, not 90 (USB requires 90). Route your single-ended and differential pair traces. Place the MDI termination within 250 mils of the 82578. The capacitor value may be traded off to. How to calculate differential impedance: Notes. To avoid microstrip modes, have h >> (w+2g) and extend component side ground away from the trace by > (w+2g). • Trace mis-match compensation should be done at the point of mis-match. Single Ended Impedance Ω. 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. 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. Stripline Trace. This calculator determines the impedance of a symmetric differential stripline pair. The differential skew is adjusted with a tiny blip on one line towards the bottom of this image. Build a model from experimental data of impedance vs. Differential traces: two traces that are driven together with equal and opposite polarity; Non-coplanar:. As the trace gets thicker solder mask has less affect. Enter dimensions: Trace width (W) mils. Differential Microstrip Impedance Calculator Note: valid for (w/h) from 0. mils: Distance between planes (B) mils: Relative Dielectric constant (Er) Differential. 48 e-0. Both LM and CM converge to zero as spacing goes to infinity. PCB Impedance and Capacitance Calculator: Asymmetric Differential Stripline. Zo (diff) is calculated to be 244 ohms, so dividing by two yields a value of 122 ohms for the semi-coplanar structure. 9 Ohms). 2mm from the ground plane below. 2. g. 8. You may wonder why it dips initially. some trace calculation examples. If it is 17mils thick on the top layer to get 100ohm differential (or whatever), make sure that no other traces also use 17mil thickness. The trace impedance or PCB impedance damages the integrity of both analog and digital signals. We have upgraded our Impedance Calculator, a free 3D field solder, which now uses the 2D numerical solution of Maxwell’s equations for PCB transmission lines. 4515. The outputs impedances can be odd, even, common and differential. Eventually, the impedance of your power delivery network. This works fine, I ordered impedance control several times - no need to change the width. 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). 0. Can I / should I add extra components to the bus traces, to reach. Visit to learn more about our other electrical engineering tools. 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. Inductance – the impedance calculator uses the Impedance value to calculate the inductance per unit length. 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). Reference layer. Just enter the given values for trace thickness. How much of an effect will soldermask have on the circuit?With PCBWay impedance calculator, you can calculate the approximate impedance of your PCB / high frequency circuit board. Differential pairs are commonly found in high-speed data communication systems, such as those used in computer interfaces (e. The Smith Chart achieves this by superimposing a grid on S11 that maps load impedance. Board Setup. Check design with the online gerber viewer, Easy and quick PCB Price Calculator from JLCPCBEEWeb provides a suite of Microstrip Impedance Calculators as follows: Microstrip Impedance Calculator; Embedded Microstrip Impedance Calculator; Wire Microstrip Impedance Calculator. KB: Prevent multiple license seats being used on one installation instance. That trace has an impedance,. x. 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. Modeling approximation can be used to understand the impedance of. But make sure you get the spacing between the diff pairs and their thickness (copper weight) correct. 22 mil wide. Microstrip impedance calculator. Calculate the differential impedance of a microstrip transmission line with this handy calculator. Classes for 50 and 100-ohm traces. *The structure may propagate in 3 modes: coplanar waveguide, coupled slot lines and microstrip. This impedance is dominated by the physical separation between your power rails, traces, and internal planes in your board. 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. Stripline. To meet those requirements I used some online impedance calculators to estimate the required trace properties for a. 020. 035 mm. Getting the Most Accurate Impedance Calculations. I wanted to use Altium to calculate the width of the trace automatically, so that it had a 50 Ohm impedance. While every trace has an impedance, we don't care about the trace reactance if the trace is only carrying DC current. In some cases, we can also use 75-ohm. This calculator is designed to find the characteristic impedance of an asymmetric stripline - a flat conductor between two ground planes. It is admittedly small, but it is non-zero. For example, with a thickness of 0. In other words, if you are designing to hit a differential impedance target (such as. There are four different types of impedance used in characterizing differential trace impedances. Every trace has capacitance between the trace and the return path of the signal on. Characteristic. The outputs impedances can be odd,. Dual Stripline. The JLCPCB Impedance Calculator computes track width values and recommended stack-ups from user-input values of board layer, thickness, copper weight, target impedance, trace spacing (for edge-coupled pairs), and impedance trace to copper gap (coplanar waveguides). This is more than the to times trace width which is recommended (also read as close as possibly). The last point in particular should give you the most accurate result, but might cost extra. Use the results from #3 to calculate the width profile with. To optimize the PCB trace impedance and stackup, you must follow the key notes below: If thin dielectric layers with high dielectric constant (Dk) cannot be. Note that Zdiff (differential impedance) is equal to 2 * Zodd, so a Zodd of 45 Ω gives us a Zdiff of 90 Ω. Z diff = 2* Z o (1 - 0. 5oz inner copper, 8 mil trace spacing) and a target differential impedance of 100 ohms, JLC's calculator suggests a trace width of 8. KB: Fail to install possibly due to lack of admin privilege or virus protection software. 25, but gives me nice trace from the module to the stub then to microcontroller. The trace width and spacing for a certain impedance may be obtained using impedance calculators. Track width (w) = 137 micron. Select a trace impedance profile over the length of the taper. To maximize signal integrity, proper routing techniques for differential signals are important for high-speed designs. 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. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion. 6mm spacing with a trace width of 0. differential trace impedance for USB (90 Ohms) on 2-layer FR4 board. The extracted model includes distributed parameters for resistance, capacitance, and inductance, as shown in Figure. 2-0. 0. Calculates the characteristic impedance and per-unit-length parameters. Use an impedance calculator to determine the trace width (W) and spacing (S) required for the specific board stack-up being used. 3. This calculator finds both odd and even transmission line impedance. 37) If H1<1. You can use a trace impedance calculator for stripline and just make the H (height above the ground plane) very large. Instant online PCB quote, get PCBs for only $2. Differential Impedance Ω. Broadside-coupled Asymmetric Stripline. View All Tools. 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. TheseIt always defaults to 10mil. 4515. The second link seems to hint that some calculators take some extra parameters into consideration. The closer you place the pairs together, the differential impedance gets smaller because LM and CM get larger. Figure 13: There are single end trace impedance and distance between traces in the pair. Now also calculates DC resistance with temperature compensation. There are some advantages to using a microstrip transmission line over other alternatives. You want to select “Microstrip Zdiff”. KB: Fail to use evaluation license with a dialog "You can use this license only on a single PC". Press the Analyze button to calculate the electrical parameters. Remember to maintain 100 Ω differential impedance. A 3D view of a complex impedance controlled PCB in. Don’t forget to check out our other. • Choose a suitable board stack-up that supports 75 Ωsingle-ended trace and 100 Ωcoupled differential characteristic impedance trace routing. 1. Differential Stripline Impedance Calculator. Open the PCB layout tool (pcbnew) and go to File > Board Setup. 5ohms and the fact that it’s nearly flat above about 800kHz). Introduction The edge couple differential microstrip transmission line is a common technique for routing differential traces. It is especially required when high-frequency signals propagate through a circuit board trace. 25mm trace. beammy. To meet those requirements I used some online impedance calculators to estimate the required trace properties for a 2-layer FR4 PCB. We care about maintaining the same differential impedance for. 8. Board. Using a differential pair to avoid common mode noise is common in audio circuits. Atlas Si for VNA – Insertion loss test system – Delta-L 4. 1. USB traces must be 90 Ohms differential. pair impedance with predifined traces’ gap. KB: Route traces between flex and rigid regions. 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. Assuming both are accurate enough. If you put that into the calculator, you will get much more practical values for the trace width. D = Separation between the differential traces. Far end cross talk is eliminated by using stripline routing. 29 mm width traces to obtain 100 Ohms ZDiff while using 0. It seems I could largely do without any impedance matching considerations, given what the trace lengths are. Differential Impedance is the impedance between two differential pair signal traces. PCB Trace Impedance Calculator. Include both the pcb dielectric thickness as well as the wire insulation in the height calculation. when two coupled tracks are used to give a differential impedance. The JLCPCB results are more reliable than (some of) the simple formula-based approaches. where Z 0,surf can be computed as specified in Eq. Single-Ended Impedance. 6) ; TanD = 0. In fab notes, give the expected impedance (100ohm differential), the acceptable tolerance (often +/-10% or 20%), and which traces are. The stripline impedance calculator provided below is useful for gaining an initial estimate of trace impedance for striplines. Home;. Choose a calculator to tune your PCB design. Single-ended signals are fairly straightforward. Using an online differential impedance calculator, the height of the dielectric layer, h, is needed. 25mm, a trace width of 0. However, to keep costs down, there are only two drill pairs, meaning that a high-speed signal may only need to travel 3 mil down a 23 mil via. 96D/H) Zo. The differential impedance of a PCB is simply the current to voltage ratio on pairs of transmission lines driven in differential mode. There are a lot of online trace impedance calculators specifically designed for differential traces. 3 V, etc. 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. The main takeaway for me: To get to around 80 ohms, I should not pull ground on the signal. 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. 6mm 4 layer PCB, 1oz outer copper, 0. The calculation looks correct, but the tracks are too wide. Enter the differential impedance you want, the trace width, the dielectric height, the dielectric constant, and the trace thickness, and click the. Keep the trace stub lengths to a minimum. Engineering/Technical. 3 shall be used. W is calculated to achieve a trace impedance (Z0) of ~50W and S is calculated to achieve a differential trace impedance of 90W. THESE FORMULAS ARE APPROXIMATIONS! They should not be used when a high degree of accuracy is required. Stripline. The ground plane helps. 0mm (4L-02) When using our free Defined layer buildup 4L-02, you will reach the desired impedances e. The calculator is set up to handle an asymmetric arrangement, where traces are not centrally located in the PCB layer stack. PCB impedance control is an important design constraint when working on high-frequency circuits. 3 CPW Structures; 3. 1. Following is the formula for differential impedance for a Stripline. In addition to characteristic impedance analysis, the signal integrity extension can perform equivalent circuit modeling of a particular trace or differential pair. When routing differential signals across common PCB materials, each trace of the pair will experience different dielectric constants and corresponding signal velocities due to the differences in static permittivity (Ɛr) of theCalculate Coplanar impedance for given PCB parameters. This has been a research topic for differential serial protocols over the last several years, and standards like USB 4 place specific requirements on broadband signal integrity metrics. 0. 1 to 3. The default units for all given values, except the subtrate. 6), the impedance will be approximately 50 Ohms. Check here: UltraCAD's new Differential Impedance calculator will calculate single-ended and differential impedance for the common configurations we all deal with: Microstrip. 1. differential signals should be at least five times the trace width away from other traces. I am developing a 4-layer FR-4 board containing a GNSS receiver (L1 + L2). Signal layer. Click on Net -> All Layers -> Line under the Spacing Constraint Set. You will want to control impedance with smaller variations in gap. Trace stubs must be avoided. Changing the stack-up will affect the calculated trace width for impedance-controlled traces; however it will not automatically update existing traces. As explained in Part 1 of this series ( Circuit Cellar 367, February 2021 [3]), PCB manufacturers can propose different PCB stack-ups, and specifying a low thickness for the so-called “top prepreg” will help to reduce the trace width. The tool implements numerical solutions of Maxwell’s equations to render accurate and consistent results. 125; Tolerances; Certifications; RoHS - Lead Free; Electrical Test;. Using a power plane as signal reference. Differential impedance: This is the impedance of a pair of transmission lines. You need to maintain a specific distance between these two tracks. Several Web sites such as the examples listed below contain additional reference information. One of the features of this type of microstrip is the coupling between lines. 25mm, a trace width of 0. e. The guides says spacing under 0. To get the correct parameters, we have to use the specifications from our PCB house and the provided calculator. 1. IPC 2141 Trace Impedance Calculator. some trace calculation examples. Description. Differential Pair Routing. characteristic impedance of the differential mode is Zd, common mode is Zc. Hello Community, iam currently designing a board that contains an 100MBit Ethernet connection. Figure 3 shows the respective p and T models used to calculate the differential impedance (Z diff). Sorted by: 1. Conversely, tightly coupled differential pairs have an air gap that is less than the trace width. 2) S/T > 5. Use the Series and Shunt Impedance Calculator: to try your own impedances; Change Grid: S11, (ZL normalized to source impedance Z0)Overview. Most often, the only specified requirement of a differential pair is its differential impedance. With t = 35 um (typical for copper with plating on a pcb), Z odd drops to 44 ohms, according to LineCalc. 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. Yet I got a ZDiff CPW with ground capable calculator: Differential surface coplanar waveguide with ground calculations: *0. IPC 2141 Trace Impedance Calculator. The spacing between two traces in a differential pair should not be more than twice the width of the traces. resistor values). This calculator allows you to add the impedance model and compute the desired trace geometry and spacing for a target impedance. signals. Most popular calculators don’t even have a box height parameter. Differential Pair Impedance Calculator Our impedance calculator features two main types of impedance models, single-ended and differential, within each trace structure. Incidentally, the trace thickness parameter does have a significant effect. e. 2 of the Microstrip Calculator, h=H1 and b=H2-H1. Tuning for your traces to the desired impedance value occurs by adjusting trace width and distance from the reference plane. But, you usually want some decent coupling between the traces, so a good single-ended impedance target for each trace is. Note 2: This and other formula based impedance calculators may easily be way off if you have thin dialectric and skinny traces (which is what we often want in order to squeeze a lot of traces into a given area). Specific spacing and impedance may be required for high-speed circuits to minimize crosstalk, coupling, and. Using this calculator, I found 100 Ohms by giving 9 mils of track width, 5 mils of track separation, 8 mils of dielectric. There are 3 types of single-ended models: single-ended non-coplanar, coplanar single-ended, and coplanar single-ended without ground. Click on Setup -> Constraints > Electrical Constraints Set - > Differential Pair Value - > Calculator >. The article will not go into the details of these other aspects that indirectly are part of the impedance controlled traces challenge. 8. Then. At the receiver, the signal is recovered by taking the difference between the signal levels on. 1. Is there any reason not to use these values? If you can fit a design with larger gaps and wider traces, then the differential impedance will be less sensitive to over-etching or under-etching during pcb fabrication. Coplanar Waveguide With Ground Characteristic Impedance Calculator. I've used 7 mil trace width with 5 mil spacing, top and bottom layers (35um copper) are 0. The surface finish is neglected. The article will not go into the details of these other aspects that indirectly are part of the impedance controlled traces challenge. We recommend the software from Polar Instruments if you want to get exact impedance calculation. As seen from the formula when D decreases, while keeping B. Use an impedance calculator to determine the trace width (W) and spacing (S) required for the specific board stack-up being used. $egingroup$ So basically your answer shows that the JLCPCB impedance calculator results are generally in the same ballpark as the proven field simulators. Gaps in signal traces impact the entire test waveform, and its single-point impedance is too high, making the entire waveform uneven. The amplitude increases as the coupling length increases up to a point. If you keep the traces short, it will work even if the impedance is. In differential pairs, each trace in the pair carries the same magnitude, but opposite polarity. 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. Printed Circuit Board Width Tool . This calculator finds both odd and even transmission line impedance. This is an approximate critical ratio. Missing by 25 microns on a 100 micron trace throws off the alignment by 25%. For example, I have differential stripline signals, which should be 100 Ohm impedance. x allows an easy way to make differential pairs and keep control of the trace length, thus the phase or skew between the traces. 77 mm gave me a differential impedance very close to 90 Ω. Geometric Parameter Definitions: 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. 1 mm trace spacing chosen in your design. They will give very similar answers. 5. Controlled Impedance; PrePreg Chart. This would be more manageable. Controlled impedance (CI) is the characteristic impedance of a transmission line in a PCB conductor and its related reference planes. • Keep single-ended signals away from differential traces – distances should be at least at least 2x the trace width. 093. PCB stackup, signal integrity and controlled impedance: Signal integrity tools: Stackup design. 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 calculator shows 90 ohms can be achieved using. 254mm. Regarding the impedance of USB signal traces the layout guidelines state: DP, DM Differential trace impedance = [DP(45ohm) + DM(45ohm)] = 90 ohm, and do not jump the DP DM signals that cause impedance miss match. Assign the trace width and spacing that will make the impedance of the differential traces - the desired impedance. There are a lot of online trace impedance calculators specifically designed for differential traces. While this calculator will provide a baseline, any final design considerations should be made towards loss, dispersion, copper roughness, phase shift, etc. Differential impedance. FYI, I followed 2nd option and values were quite similar. Separation between the coupled differential trace pairs must be 1x. 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 trace along with the dielectric thickness and constant of the coupled line. This assumes ~0 trace thickness.