0 high-speed. This definition effectively makes it equal. Coplanar Waveguide Calculator. Dimensional units: mm mils. 2In real high speed signal pairs (like USB3) the pins are swappable to avoid the need to cross the traces. g. D+ and D-) _P/_N (e. A common approach is to create a net class or differential pair class that includes these nets, then create a routing rule that targets this class, as shown in the images below. Altium Designer makes it easy to calculate geometry when you need to calculate impedance for differential pairs. i know that i can use. 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 . This makes the problem of determining impedance much more complex, and building an initial lossless model requires a larger set of formulas from Wadell. When you are creating your schematic, you must use one of the following suffixes when naming your differential pair nets: +/- (e. g. An example of this calculation using the Si8000m Quick Solver is shown below in figure 4. look at a differential source driving a twisted pair to the FDA. Using the KiCad Impedance Calculator. Compatible with Flex PCBs and Turnkey PRO service. This sheet has the FTDI chip which converts the input serial signal into a USB differential signal. First, consider a microstrip. Following equation or formula is used for Differential Microstrip Impedance Calculator. Following is the list of useful converters and calculators. It is often said that differential pairs do not have a return path, which is not true. 1. Ask the board manufacturer for the values. is the impedance between two differential pair signal traces. 19mm) traces with 7. This will give us the appropriate trace width and trace separation for the desired differential impedance. Thus a "differential pair" any long distance apart will have an impedance of 98 ohms, without any coupling between the lines, i. Design Parameters. For differential pairs, this meant that there was a differential pair impedance requirement, or rather an odd-mode impedance requirement. Characteristic. They are recommening to use 3th party calculators. The PCB Impedance Calculator in Altium Designer. 6 inches - this is very easy to do; If you can access a differential impedance calculator, then use differential. High-speed differential pair signal traces need to be routed parallel to each other with a constant spacing between them. manufactures will have a preferred tool that PCB designers can use to calculate the Impedance but there are also many available online. Microstrip construction consists of a differential pair and a single reference layer (typically ground). This calculator is designed to calculate the characteristic impedance of an edge-coupled microstrip. Select the same nets to analyze and run the simulation. 14 • What you should be able to do after this module 1. Disc Air Capacitor Calculator; Impedance Calculator : XL, XC; Inductors, Transformers. Z 0 now meets your requirements. But in your differential pair, each line will have its own characteristic impedance, lower than 100 Ohms but higher than 50 Ohms (for instance a quick computing in Saturn PCB give me 77. 5mil (7628 prepreg) when tracks are inside. The concept of Shield Transfer Impedance (Zt), introduced by S. Altium Designer’s rules-driven design engine allows you to define trace length tolerances in differential pairs and across signal nets. We’ll go over how differential pairs can hel. 3mm, as shown below: This increases the impedance slightly to 91. Signal layer. Advanced simulation and analysis tools can. 5 mil (2116 prepreg) or 8. This transmission line calculator was. If I calculate it for embedded edge coupled differential pair, it is still only 39. The resistance value chosen for the two resistors will be referred to as R D (for d rain resistance). Calculate Z diff, Z com, Z odd, Z even from transmission line parameters 2. You can see. There is a slightly different, but tightly. So, to calculate the differential impedance of Figure 1, simply calculate the impedance of Figure 3, and double it. Differential Protocol: Select the desired protocol from the dropdown list, this list will autofill the Target ZDiff edit box. This technique is used for routing internal layer differential pairs. The stackup on the left side of Figure 2. In the special situation for which there is no coupling to ground, Differential impedance equals the Characteristic. USB traces must be 90 Ohms differential. The questions are mostly on the inner layer differential impedance item [4] below. I am trying to design a CAN bus node. This calculator is designed to calculate the characteristic impedance of a broadside couple stripline (see diagram below). In the case where you are routing differential pairs, then the potential between the two pairs will always be opposing (i. The impedance calculator in the Allegro stack-up editor uses a static 2D field solver by default (bem2d). Differential Impedance in Constraint Manager Advanced Constraints can be used to view the Differential Impedance in Constraint Manager. A golf handicap calculation based on the score achieved for nine holes of golf. Converts short and long line . Layers: Total number of copper layers in. Use the same trace widths throughout the length of the trace. Common-mode impedance occurs with the pair driven in parallel from a. Thus, for optimal performance the resistors and MOSFETs must be matched. ETA: USB 2. PCB Structures / Discrete Structures / Signal Management. CSI-2 interface data pairs require a 100 ohm differential impedance. Details: In the list below, [1] is the reference design stackup information; [2] and. The Signal Integrity tool is examining the series termination needed based on the line's characteristic impedance If you are examining a trace in a differential pair, the Signal Integrity tool is still only used the characteristic impedance, not the odd-mode impedance. A differential amplifier multiplies the voltage difference between two inputs (Vin+ - Vin-) by some constant factor Ad, the differential gain. Cross-hatched copper plane in a flex stack-up for controlled impedance. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. If a different frequency is required, pick. to NFThe impedance of the structure is the ratio of the voltage between, and the current in, the conductors. The PCB design tools in Allegro include an impedance calculator that will help you size your traces so that they have defined characteristic impedance. on layer 3 from the top, between power and ground plane. These equations delineate between single-ended and double-ended lines, with the latter used in differential pair setups. . In Altium Designer you can easily change the width of both of the differential pair tracks, but if you do so the gap of the diff pair changes depending on the change of the width. A cross-hatch plane is shown in the image below. Eurocircuits also calculates the correct Differential Impedance values using the correct formula and not a ‘Rule of Thumb’ method. I used the KiCAD PCB calculator, asked the PCB manufacturer about the tangent loss (0. Use via-s (absolutely not recommended for impedance-critical routes) hack the connector and remove some of its SMD pins, and wire one pair under those pins. This will be specified in your controller's datasheet in the DDR4 interface specifications. Skin Depth Calculator. In the time domain, we only care that the two ends of the differential pair cross the halfway transition between the HI and LOW states (assuming binary) at the same instant in time. 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. Coplanar Waveguide With Ground Characteristic Impedance Calculator. The latter for embedded dual stripline layers only. Its utility stems from its ability to. Differential Impedance Ω. g. If you don't have access to a differential impedance calculator, or you don't know how to calculate it, then just keep trace lengths less than 0. pair impedance with predifined traces’ gap. For now let us focus on the single ended impedance. 1 has six signal layers, but only has one pair of planes closely spaced. Also, it has got. Note: The results are only for approximation and rough estimation, the final values and the. Saturn PCB - Toolkit for Impedance Calculation. Based on Zo Equation Per: IPC-D-317A:. 2. Follow the 8W spacing for differential clocks (or explore other rules) Even greater spacing is needed for high-speed differential signals. The IPC-2141 trace Impedance calculator will help make initial design easier by allowing the user to input basic parameters and get a. So, the trace width and distance to adjacent reference plane is determined by the desired. 1) isn’t overly complicated. . The result is a signal reflection back towards theYou can calculate the characteristic impedance of the differential pair using an online calculator, a dedicated transmission line calculator like Polar, or a 2-1/2 or 3-D EM simulator like Ansys or HFSS. ’ Give a name to this rule (100 ohms in this case) and double-click. You will need to know the dielectric constant and the copper thickness to calculate trace impedance. When you calculate differential impedance you still need to have a ground reference. Backwards crosstalk creates a pulse width that is twice that of the propagation time of the pulse traveling the coupling distance. This assumes ~0 trace thickness. 75 m A = 9333 ohms. The Impedance Calculator is a tool which allows a quick pre-layout estimation of several kinds of line impedances between different layers. I used the Altium`s impedance profile calculator and got the parameters, but then I double checked with a Saturn PCB tool - the results were significantly different (Picture 2). Details: In the list below, [1] is the reference design stackup information; [2] and [3] are the processes to get the result close enough to the reference design target so as to know the tool is valid; and [4] is the calculation in question because it is either 5. Capacitance – the impedance calculator uses the Impedance value to calculate the capacitance per unit length. 5oz inner copper, 8 mil trace spacing) and a target differential impedance of 100 ohms, JLC's calculator suggests a trace width of 8. But, you usually want some decent coupling between the traces, so a good single-ended impedance target for each trace is between. I am routing differential pairs in Altium 20 and using controlled impedance profiles. Useful converters and calculators. When you are creating your schematic, you must use one of the following suffixes when naming your differential pair nets: +/- (e. Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. > A good starting point is to ask you board house give you the widths and spacing for your stackup. This calculator finds both odd and even transmission line impedance. For double termination, the source needs to provide R O = 50 Ω on each side for a 100-Ω differential output imped-ance, and the line needs to be terminated with R L = 100 Ω. From it, apart from making all traces the same length from camera sensor to cable connector, I believe the rules I need to follow are: Differential impedance of 100 Ohm. Your relay is single line with characteristic impedance of 50 Ohms. Twisted Pair Impedance. 6mm thick. 2. Atlas Si for Touchstone – PCB Insertion loss processing with Delta-L 4. The Differential Pair Impedance Calculator simplifies the process of designing PCBs and high-speed communication systems, ensuring that signals are transmitted efficiently and reliably. The i. This application note provides a brief theoretical background to the impedance calculation methods used in the Polar Si series field solvers. With t = 35 um (typical for copper with plating on a pcb), Z odd drops to 44 ohms, according to LineCalc. 6 ohms and Z even = 110 ohms for your geometry, very close to your result. 25. Return loss is an important parameter that indicates how well the impedance matches with aFor differential vias, stitching vias can affect the impedance, but the impedance is much more sensitive to antipad sizes and layer arrangement/Dk value on each layer. Description. The specific trace width and the spacing are required to calculate the particular differential impedance. The tool implements numerical solutions of Maxwell’s equations to render accurate and consistent results. Just as. To find the impedance of a capacitor (Zc) and an inductor (Zl) in an AC circuit, you use the following formulas: For the capacitor: Zc = 1 / (2πfC) For the inductor: Zl = 2πfL Where f is the frequency, C is the capacitance, and L is the inductance. Differential pair impedance depends on a lot of variables in reality,. There’s an actual free 2D impedance calculator out there (arbitrary transmission line calculator, or ATLC). Two single-ended transmission lines with coupling are also known as a differential pair, as shown in Figure 5. To calculate this, you need some values. The example below shows how adjusting the stitching via placement could affect a differential via. Simons, "Coplanar Waveguide Circuits, Components, and Systems", Wiley. The targeted impedance for diff pair is 100 ohms, which is dependent on the width/space between conductors and hight to the reference plane. You can calculate it with the following equation: Z (z) = V (z)/I (z). beammy. 6. 6 inches - this is very easy to do; If you can access a differential impedance calculator, then use. 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. There are a lot of online trace impedance calculators specifically designed for differential traces. mils: Distance between planes (B) mils: Relative Dielectric constant (Er) Differential Trace Impedance: ohms: References. This value is often given the name “differential impedance. The grounded differential coplanar wave guide is the differential version of the grounded coplanar wave guide and is used in high-speed digital systems that require maximum noise immunity. The interactive routing and differential pair length matching features in Altium Designer® can be used alongside an integrated electromagnetic solver in the Layer Stack Manager. You will need to know the thickness of the dielectric you will be using as well as the relative permittivity (dielectric constant). When enabled. TransCalc is an open-source impedance calculator of various transmission lines based on common closed-form approximations. $$Z_{0_{diff}} = 2Z_{0_{odd}}$$ Common Impedance. High-quality circuit boards as prototype and series at reasonable prices. 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. It is important to determine the characteristic impedance of a twisted-pair cable because this impedance should match the impedance. e. 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. 75 mA corresponds to a CE range of 1V to 8V. 5 mil (2116 prepreg) or 8. 293, 50% of the copper removal can be achieved. Length matching is required per segment, and any length added (typically a ‘serpentine’ section) for the sake of matching a pair should be added near the location where the mismatch occurs. . Note: valid for (w/h) from 0. Even mode impedance for commonly-driven transmission lines . 004” line. Advanced simulation and analysis tools can. Ethernet lines are differential pairs with a differential impedance of 100 Ohms. Differential Stripline Impedance Calculator. Schelkunoff in 1934, is a very convenient parameter for the prediction and control of EMI coupling through cable shields. As discussed in the first section of The MOSFET Differential Pair with Active Load, the magnitude of this amplifier’s gain is the MOSFET’s transconductance multiplied by the drain resistance: AV = gm ×RD A V = g m × R D. Is this a good practice for Ethernet? This is a capture of the PCB right now: This is the schematic that I am using. Route differential pairs symmetrically and keep signals always parallel. Our Impedance Calculator uses a 2D field solver to calculate near-end crosstalk based on the following equation: NEXT = V b /V a = ¼ (C mL / C L + L mL / L L). Even mode impedance for commonly-driven transmission lines . The controlled impedance method applies to any trace that handles high-speed or high-frequency signals. Differential Pair Impedance Calculator. Note that the net pair must be named with net label suffixes of _N and _P. Calculate Z 0 as normal Microstrip, until you get the desired value, e. About Saturn PCB Toolkit (latest v8. There have been trace routing tools available for a long time that help with differential pair routing. 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 (for edge-coupled pairs), and conductor-to-ground gap (coplanar waveguides). D+ and D-) _P/_N (e. Only a 2D field solver can accurately calculate the differential impedance. Even mode impedance is defined as impedance of a single transmission line when the two lines in a pair are driven with a common mode signal (the same amplitude and the same polarity). Controlled impedance traces are determined by their physical dimensions and the property of the dielectric material used in the circuit board. In this study, Keysight’s Path Wave Advanced System Designer, ADS, which has an integrated 2D field solver, was used for the analysis of a virtual prototype. 0 and CAN-FD might be slow enough to get away without it (and I'm honestly not sure, the performance will depend on the specific configuration), but if I were reviewing a layout with diff pairs without a ground reference I would be very unhappy with it. The most commonly used instrumentation. To use this calculator, simply input your microstrip geometry and Dk value, and the tool will return the differential impedance value for a pair of microstrip traces. 331 1 2 5. Visit to learn more about our other electrical engineering tools. Modeling approximation can be used to understand the impedance of. 0 for analysis with Si9000e. For complex impedance matching, the input impedance is important as this is the impedance seen by a. 08mm - this is the border of manufacturability, I don't think it is practical to go there but for the calculation it is just fun - and I get some 31Ohms. Give it better GND connection if possible. Eurocircuits’ Impedance calculator uses real values as defined in the supplier’s data sheets. 4000 Enterprise Drive, Rolla, MO 65401 (573) 341-4139 (573) 341-4477; ygtpv@mst. Joined Jan 22, 2008 Messages 51,800 Helped 14,703 Reputation 29,682 Reaction score 13,944 Trophy points 1,393 LocationWhile there are a number of online calculators that calculate the characteristic impedance from the input geometry, they are all based on approximations. Another example of using large distances to separate out unwanted components might be to calculate the impedance of a. Calculating the impedance . The main takeaway for me: To get to around 80 ohms, I should not pull ground on the signal. PCB manufacturer normally provides information about PCB stackup and track geometry. This is a calculator used for determining the characteristic impedance of a microstrip. The impedance calculators below are completely free to access and use. Activity points. 331 1 2 5. Impedance Calculators. Coplanar Waveguide Calculator. Not too tricky. Formula: Applicability: w ÷ t ≤ 0. The odd mode impedance is the impedance of one transmission line when the pair is driven differentially. 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. Agilent's LineCalc tool calculates Z odd = 50. 75 inches without impedance control; Keep the differential pair length mismatch within 0. Differential Impedance ($$Z_{0_{diff}}$$): The impedance between the two lines with opposite polarity signals. . Re: Calculating Differential Impedance for USB Differential Pair. The track widths should. Differential Stripline Impedance Calculator. The differential pair—sometimes called the long-tailed pair—is a widely used building block in electronic circuits, particularly in op amps. The single 50 Ohms is the impedance of a single-ended transmission line that has a ground connection. This curve defines. AC coupling capacitors can be positioned anywhere throughout the differential pair’s length. D_P and D_N) KiCad looks for these suffix pairs when using the differential pair routing tool during PCB layout. You can make your own spread sheet using formulas provided by Wedell's book "Transmission Line Design Handbook" page 196, 197, 198 (attached)Relative dielectric constant (er) mm. Impedance Calculation for PCB Designers - Altium. 8. Both gives me only 20 Ohm differential impedance. A PCB impedance calculator is necessary to set the constraints for trace structures during fabrication; they can vary in complexity, speed, and accuracy. If your differential pair has 100 ohm (differential) characteristic impedance, you should just design the uncoupled parts of the lines to have 50 ohm (single-ended) characteristic impedance. Reference: R. The calculator shown below uses Wadell’s. Length of both tracks should be the same. 5 mil as the thickness of 3313 prepreg when the controlled impedance tracks are on top/bottom, use 5. For a printed circuit board (PCB) this is a pair of traces, also known as a differential pair. I need to route 100ohm differential pair without GNd I can't find any PCB calculator for parallel routing on one layer. 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. Differential Microstrip Impedance From Zo. 68 mils. Controlled impedance is typically applied in single-ended microstrip, embedded microstrip, stripline differential pair, and planar PCB transmission lines. 1 is an example of making tradeoffs between routing layers and power plane capacitance for a ten-layer PCB. Once the option is active, click on the shortest trace and move the mouse. The characteristic impedance (Z o) of coplanar waveguide with ground or microstrip lines with signal side ground plane can be calculated using the active calculator or the equations at the bottom of the page. Microstrip Impedance Calculator. Learn how to design. A microstrip line is a type of electrical transmission line used to convey microwave-frequency signals and consists of a conducting strip separated from a ground plane by a dielectric layer known as the. 3. Calculation tip for defined Z 0 as well as Z Diff. PCB Impedance and Capacitance Calculator: Asymmetric Differential Stripline. By Perrine Juillion / April 8, 2020. In other words, if you are designing to hit a differential impedance target (such as. 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. The Smith Chart achieves this by superimposing a grid on S11 that maps load impedance. It also explains the factors that affect the impedance, such as trace width, dielectric constant, and frequency. Similarly, external fields can induce currents in a differential pair that are not equal in amplitude and opposite in phase. Before we can start routing the PCB, we need to define Design Rules for our differential traces. 9. . I tried using different line width (10mils,15mils,20mils,25mils,30mils) of the differential pair but it doesn’t help me. Differential Pair Impedance Calculator Calculates the differential pair impedance of a balanced line. The characteristic impedance is given by: Eq. D+ and D-) _P/_N (e. 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. It is only equal to double the characteristic impedance in certain cases. This PDF document provides a comprehensive guide on how to calculate the impedance of various PCB structures, such as microstrip, stripline, and differential pairs. $egingroup$ So basically your answer shows that the JLCPCB impedance calculator results are generally in the same ballpark as the proven field simulators. (Differential Impedance, Ohms) = Note: 1oz = 1. Let's match the impedance of the same signal since differential pair routing is completed when the impedance is matched properly. Although widely applied to coaxial cables against EMI susceptibility problems, the Zt parameter can be easily extended to coaxial cables EMI emissions. Using a differential pair to avoid common mode noise is common in audio circuits. Maximum near end channel to channel cross talk for 100 Ohm, 5 mil wide differential pairs, as the channel to channel edge spacing increases. 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). Other calculators will use different. The Si8000m assumes negligible insertion loss in the transmission line; should you wish to model insertion loss the Si9000e adds. If you don't have access to a differential impedance calculator, or you don't know how to calculate it, then just keep trace lengths less than 0. For differential pairs, see the addition at the end of the tutorial. There are single end trace impedance and distance between traces in the pair. Try it now for free. The trace width (0. is the impedance between two differential pair signal traces. Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. Hence, without loss of generality, one. Tightly coupled pairs (within a pair) are quite common and this has the advantage of having a somewhat higher single ended impedance on a per track basis within a differential pair which is often easier to implement. Using the KiCad Impedance Calculator. Capacitance (C) = pF/ cm. High speed digital designers should. Note: The 6-Layer board temporarily only provides JLC3313 Stackup. Note that the driver output impedance may be configurable among various values. 03556mm. This calculator determines the impedance of a symmetric differential stripline pair. 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. Enter your board parameters and get instant results. 36 mm substrate, has an impedance to ground, unbalanced, of about 49 ohms. This calculator computes the characteristic impedance of a twisted-pair cable based on its dimensions. 6mm FR4 PCB with 7628 type stackup (4 layers), the above specifications usually result in 4. g. Differential Impedance Differential Impedance: the impedance the difference signal sees ( ) ( ) 2 2( ) Z 0 small I V I V diff Z diff one one = = ≈ − Differential impedance decreases as coupling increases +1v -1v I one x I two How will the capacitance matrix elements be affected by spacing? C 12 C 11 C 22 Eric Bogatin 2000 Slide -18. When the two lines are far. NOTE: The formulas used in the program are valid for 0. Distance between pairs should be (traces on top layer = microstrip) 4 times the layer. net Forum comes closest to the proper track width. Reference: R. In differential pairs, each trace in the pair carries the same magnitude, but opposite polarity. Other calculators will use different equations for the same system, depending on the relevant approximations used in the derivation of the formula. • Differential pairs should be routed away from all other traces. In case I reduce the width and the distance of tracks to 0. Use that. 2) S/T > 5. 3. It is defined as the ratio of powers of the differential gain to the common-mode gain found in equations (2) and (3). The two traces of a pair should be symmetrically routed. Copper. ; To. In case you need to calculate single ended or differential pair impedance on your PCB, try following links: I use Microstrip & Stripline calculator developed by Jean Nicolle. Differential pairs: even or common mode? PCB impedance calculator – Single ended / Differential pair. Sierra Circuits’ Via Impedance Calculator uses the physical dimensions of a via to calculate its capacitance, inductance, and impedance. g. To achieve impedance control, PCB design software with an integrated field solver can help in designing the right trace width for the HDI layer stack-up. look at a differential source driving a twisted pair to the FDA. The 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. Differential impedance is twice the odd mode impedance. The values you get from an online differential pair impedance calculator corresponds to an isolated differential pair, they do not consider the load component and they are not calculating the input impedance. In high-speed digital protocols, data is sent over single-ended traces in a PCB that is impedance controlled; each individual trace is designed to have a specific impedance. Unfortunately Online Calculators are deceiving unless you actually draw the numbers and understand the ratios and tolerance effects. With the differential microstrip impedance calculator in Altium Designer,. Differential impedance, Z diff, is the impedance between the two conductors. I use the software a lot to calculate impedance, maximum current for t. But there's a ground between R7 and R8!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. It is important todetermine the characteristic impedance of a twisted-pair cable because this impedance should match the impedance. 5. how to reach 120Ohm impedance on a 4 layer board? (I use JLCPCB standard 4 layer stack-up, and with their calculator I don't reach 120Ohm for single ended and for differential I only get close with 3. The distance between the differential pair should be decided as per the stack-up design. A value of Z Line = 100 Ω is common for twisted-pair cables. The other yellow rectangle is the USB connector. In general, it works and can establish a Link with 1 Gig, but when exchanging multiple Gigabyte of Data it starts to cut out and collect RX Errors. There are various ways to de-skew a differential pair: in the via anti-pad area or in the trace. For microstrip traces, a solid ground plane is needed under the signal traces.