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Questions tagged [length-matching]

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Get Package Delays from IBIS R_pin, L_pin, C_pin and length

How can I calculate package delays (ps) from the resistance, capacitance, inductance and internal length (µm) of each pin? When I asked the component manufacturer for the package delays, they just ...
Dan's user avatar
  • 133
4 votes
2 answers
1k views

Which is preferred over differential pairs: trombones or sawtooths?

I have been told that trombones are much better to use than sawtooths, even if sawtooths may be prefered in some certians scenarios. Here I have added trombones to the differential pairs. If I had ...
euraad's user avatar
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1 vote
1 answer
60 views

How is length adjustment calculated if you have a pull-up resistor?

Let's say that I have a point A and a point B. In between there must be a conductor. It must have a certain length. But I have to hang on to a pull-up resistor as well. But I can do that at point C. ...
euraad's user avatar
  • 1,324
1 vote
1 answer
92 views

What happens if there is an impedance mismatch on differential pairs? [closed]

What do we encounter if the impedance changes along the way? For example, what kind of problem can we encounter when one of the two complementary PCB's is 90 ohm and the other is 100 ohm? For example, ...
esat's user avatar
  • 51
4 votes
1 answer
84 views

DDR2 CLK vs DSQ vs ADR length matching

I am tracing my first DDR2 with Cyclone V PCB and I can't find exact information about CLK vs DSQ vs ADR length matching. External Memory Interface Handbook Volume 2: Design Guidelines from Intel says ...
kornev.online's user avatar
1 vote
1 answer
244 views

What length of nichrome wire would I need to create a hand warmer to reach a max of 70°C?

The following are the details of the wire I have: Nichrom 80, 32 Gauge (0.2744 mm diameter), measured resistance 6.84 ohms/foot or 22.44 ohms/m. I'm planning on powering this only via USB so my max ...
VisuaL HippocracY's user avatar
4 votes
3 answers
641 views

PCB design for high-frequency differential lanes (PCIe and USB)

I have designed an M2 adapter which converts from KeyE to KeyM. Practically this means my board can be inserted into a KeyE slot, and it can host a KeyM SSD. Gray rectangle is the KeyM socket on my ...
Daniel's user avatar
  • 969
0 votes
1 answer
159 views

Why do PCB designers opt for serpentine tuning and switchback tuning over spiral patterns when addressing length matching in their designs?

I am currently researching the length matching problem in the PCB EDA domain and am curious as to why tools such as Allegro and Altium primarily use accordion, trombone, and sawtooth patterns to ...
David Lee's user avatar
0 votes
0 answers
391 views

Is length matching required for MII signals

I'm using this KSZ8041MLLI device and this is its Hardware checklist I'm using the MII Interface between this PHY and the MAC Controller (STM32 MCU) on the same board. My question is whether we ...
user avatar
0 votes
1 answer
903 views

USB3.0, 3.1 differential pair wire length matching

I have a question about USB 3.0 wire differential pairs length matching. As we know, the length matching is required and can be calculated when designing the USB3.0 PCBs. But what about the wires? If ...
Xiyao 's user avatar
0 votes
1 answer
210 views

1Gbps serial bus length matching

How tightly should trace lengths be matched for a 1Gbps serial databus? It seems to me that 100ps (15mm) should be more than sufficient. However: The Raspberry Pi Computer Module 4 (CM4) datasheet ...
Mike's user avatar
  • 533
1 vote
1 answer
599 views

How do I length match different signal classes for DDR3 or DDR4 routing on a PCB?

DDR3 and DDR4 memory routing can be confusing to for length matching because of the many tolerances and specs of all the different busses. How do I length match different signal classes for DDR3 or ...
Voltage Spike's user avatar
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0 votes
1 answer
383 views

Length matching/differential pairs and distance to polygon and other layers

If you have length matching on the inner layer of 4 layer board: Do you need any minimum or maximum distance to the adjacent layers above and below? Are there any rules of thumb? Also is there any ...
exzb's user avatar
  • 89
-1 votes
1 answer
385 views

Trouble understanding length matching requirements

I am having trouble understanding where manufacturers are coming up with their length matching requirements. For example, I am looking at length matching for RGMII between a MAC and PHY. My ...
mooshoomatt's user avatar
1 vote
1 answer
846 views

Intra Pair Length Mismatch Tolerance For 12.5Gbps signals

I'm making a high-speed transceiver design and want some direction regarding layout of trace length from P to N. The speeds will be up to 12.5Gbps. I have been informed by a equalizer manufacturer ...
Chance K's user avatar
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1 vote
1 answer
4k views

How to change track width in Altium for already placed tracks

I have a PCB with 8 layers and hundreds of tracks on different layers that already placed and length matched. I have to change again the track width to achieve the 50 Ohm impedance again because we ...
Majdgh's user avatar
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1 vote
1 answer
672 views

Length matching, Routed or Signal on Altium?

I have searched some information about the diference between Signals and Routed on the PCB Tab in Altium, and I understand it, but, when you have to do a length matching, Which is the best option? The ...
Juanma's user avatar
  • 400
1 vote
1 answer
314 views

Differential Impedance vs length matching vs IC manufacturer requirements

I'm working on a PCB with a USB 3.0 controller (TUSB7320, Texas Instruments) with SuperSpeed signals and High Speed Signals. There are some specific requirements about impedance and length matching. ...
Juanma's user avatar
  • 400
1 vote
1 answer
1k views

PCIE Gen 2 Intra-Pair Skew

I am about to make a revision of a PCB that has 60 mills of Intra-Pair Skew in PCI-E (Gen 2) RX differential pair: Considering the capacitors the skew is ~50 mills: this is the relevant part of the ...
Firas Abd El Gani's user avatar
2 votes
0 answers
597 views

Differential pair length matching considering phase

According to Microchip's document Implementation Guidelines for Microchip’s USB 2.0 and USB 3.1 Gen 1 and Gen 2 Hub and Hub-Combo Devices, the Superspeed differential pairs should be length matched ...
Rocketmagnet's user avatar
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1 vote
1 answer
398 views

Routing 5 differential pairs over a short distance with limited space

I have 5 differential pairs (4-lane MIPI-DSI) going from left (SOM header) to right (FPC connector). As you can see on the right, for each lane, the signals end on opposite ends of the FPC connector. ...
Genoil's user avatar
  • 258
0 votes
1 answer
403 views

DDR3 skew matching for microstrip and striplines

I am designing DDR3 pcb first time so I started from guide about pcb design: https://www.youtube.com/watch?v=ZNq_Ulm8cTk#t=32m As I understand using only stripline ...
user3583807's user avatar
1 vote
2 answers
620 views

PCB - matching length - relevant in that case?

I am trying to design PCB with 85 MHz signal traces between IC and connector (the FPGA board will be connected to this connector). This connection contains 28 data signals and one clock signal. I ...
bLAZ's user avatar
  • 121
3 votes
1 answer
222 views

DDR Trace Length Inside Package from Simulation Model

The DDR4 in question is a Micron MT40A512M16JY. From the vendor site, you can get the datasheets, specs, sim models. I assume from the sim models you should be able to see the trace length of each ...
minghua's user avatar
  • 555
2 votes
3 answers
5k views

differential pair impedance and length matching

I'm designing a high speed circuit (MIPI-DSI) so I have to carefully layout the tracks. Correct track impedance is the first point usually made in various online sources I've found on the subject, so ...
Genoil's user avatar
  • 258
1 vote
1 answer
171 views

Which is better, less crosstalk or less skew?

I'm designing a board that has a LVDS 2.5V interface with 30 lanes clocked at 600MHz and DDR. This is going from one chip to another chip which could be placed right next to it, there are no other ...
Alex I's user avatar
  • 3,491
0 votes
2 answers
649 views

Preferable pattern for differential length matching

When the positive and negative tracks of a differential signal are not equal in length, we add some bumpy patterns in the shorter track to make them equal. On the other hand, we usually have a rule ...
M.H's user avatar
  • 51
1 vote
1 answer
1k views

Side of length matching within a differential signal

When we are matching the length of positive and negative tracks of a differential signal in a PCB, is the position of matching important? Does it matter we match the length immediately after the ...
M.H's user avatar
  • 51
1 vote
0 answers
139 views

How far away can DDR3 memory be placed from the SoC?

I thought of an idea where i have a pcb with a soc on it, and a seperate one with the DDR3 memory that can snap into each other. This way i can replace or debug specefic parts of the system and have e....
user avatar
2 votes
1 answer
1k views

Quad-SPI (QSPI) net length mismatch

I am trying to make a good layout for the LAN9252 mac and STM32F7 controller, running at 80 MHz and I had to route data tracks with different lengths. The question is should I use nets lengths ...
kvazibog's user avatar
7 votes
3 answers
719 views

DDR(2-4) Training and Length Matching

Today I learned about the concept of memory training for DDR2, 3, and 4 (I'm not sure if DDR1 has it). The purpose of memory training is to correct for skew in data, address, and command bits being ...
cr1901's user avatar
  • 504
0 votes
1 answer
4k views

LVDS: length matching within a pair and between pairs

I'm interested in the LVDS communication between a Zynq (Xilinx, xc7z020-1C) and a camera (ON semiconductor Python 1300 NOIP1SE1300A−QDI). I have read some articles about USB2.0 where the maximum ...
Marmoz's user avatar
  • 336
2 votes
2 answers
10k views

Why is length matching important for high-speed signals?

Broadly speaking, I understand that PCB trace length matching is important from signal timing and signal integrity point of view, but I want to know some more specifics about these two parameters and ...
LoveEnigma's user avatar
6 votes
3 answers
3k views

Does crystal leads have to be same length?

I have always managed to keep the length of crystal resonator leads at the similar length. In the application I am working atm however, I noticed it would be suitable to place the crystal in a way, ...
Łukasz Przeniosło's user avatar
3 votes
1 answer
1k views

PCB trace length matching for High Speed signals with known frequencies

I am designing a PCB with High speed video interfaces and I would like to know the way to calculate the maximum tolerance that I can count on while I am length matching all the traces. When I routed ...
Dimitrios Torssøn's user avatar
3 votes
1 answer
2k views

Is it good practice to length match all traces of DDR3, or are only data traces important? [duplicate]

I am researching single board computers with the hope of designing on at the end of this, I am at the stage of DDR3, but can't find any good info on routing ddr3, regarding what traces need to be ...
Alex's user avatar
  • 562
16 votes
1 answer
3k views

Would it be considered good practice to match the lengths of UART's Tx/Rx traces?

I am assuming the answer would be yes since Tx/Rx pins are used to send data back and forth, or is it of such a low frequency that such thing is not required?
Alex's user avatar
  • 562
0 votes
1 answer
310 views

DAC/ADC lines length matching

I am using DAC3484(dac) and xc7k160t-1ffg676(fpga) in my design. DAC is interfaced to FPGA. DAC data rate is 153.6MHZ. DAC data lines should be length matched within some tolerance. How to decide that ...
suma's user avatar
  • 1
8 votes
4 answers
8k views

Meandering traces necessary for 24-Bit parallel RGB LCD interface?

I am working on a project that interfaces an Atmel SAMA5D3 MCU with a LCD TFT display. The interface between both is 24-Bit parallel RGB with HSYNC and VSYNC signals. The resolution of the display is ...
Phillip Schuster's user avatar
2 votes
3 answers
1k views

High-speed clock line crossing under data lines

I'm interfacing an SDI video de-serializer with an HDMI transmitter. The de-serializer splits the video signal into 20 parallel lines and one clock line. Because the digital video data is high speed (...
Dan Laks's user avatar
  • 8,604
3 votes
1 answer
1k views

PCB data trace lengths tolerable difference for high frequency

I have to interface a camera to a controller using the DCMI protocol for my project. I have around 17 (data+control) lines which are used with the camera. The frequency of operation is about 10 MHz. ...
Sandra's user avatar
  • 31
5 votes
2 answers
227 views

How much difference in net length is ok?

Sorry, but I couldn't find a better title. Consider the following: I have an address/data bus interface. Intended frequency of the D/A bus would be around 10-50MHz. According to the datasheet of the ...
Tom L.'s user avatar
  • 8,089