The matching device placed at the end of a trace that is acting as a transmission line. This termination prevent reflections from the end of the line and ensures a complete transfer of energy in the waveform into the receiving unit.

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3answers
82 views

How to choose the impedance of a BNC adapter?

I am trying to set up lab equipment to measure my soon-to-come sample, but I couldn't get my mind around one thing, impedance termination. I will tell you what I have, what I want to get, and my ...
1
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1answer
136 views

Terminating unused unity-gain Unstable op-amp

I am trying to terminate the unused unity-gain unstable op-amp. I have tried to terminate it with the typical unity-gain stable configuration ...
5
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1answer
512 views

Why is there such a huge price range for BNC terminators? [closed]

I wanted to buy some standard BNC 50 Ohm terminators and was surprised when I saw multiple offers with prices well above 20€ per piece. I found others for around 2€ (same online shop) and now I am ...
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1answer
61 views

USB data serial termination resistors. Need them for STM32F2 micro? If so, what wattage?

I'm a little confused. The STM32F2 datasheet says only this, vaguely stated in the features: HNP/SNP/IP inside (no need for any external resistor) Is that referring to the D+/D- termination ...
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1answer
154 views

What should I do with the unused Op-amp inputs?

I am building a simple inverting operational amplifier circuit where I am using a chip with dual amplifier. I am only using one of the two amplifiers. What should I do to the unused amplifier's input ...
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1answer
60 views

What should be the size/package of Bob Smith Termination resistor?

We have run into a layout issue where the size/package of the 75R resistor used for Bob Smith termination on unused Ethernet pins is in question. The current package of this resistor is 1206 and we ...
0
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1answer
123 views

Transmission line: Why do longer traces cause signal reflections?

As the question says, I want to know why do longer traces/longer lengths of non-terminated signals of the PCB cause reflections and not the short length ones? I am ignoring the negligible amount of ...
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0answers
59 views

For wrong termination resistor uses

Over 485-interface slaves are connected as multi drop, physically daisy chain. Those have built-in termination resistor, and the value is 120 ohm and no select switch for termination on/off. So it ...
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4answers
1k views

What and Why's of termination?

I am new to electronics, and don't understand what is termination and why it is needed, especially in digital communications. Thanks
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0answers
70 views

DDR2 memory interface and requirement of termination voltage VTT

I am currently designing a board with Freescale's K series microcontroller and a DDR2 SDRAM memory chip. The interface is point-to-point with only one DDR2 memory interfacing to the microcontroller. ...
0
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1answer
50 views

How subtle or dramatic are the effects of a impedance mismatch by a certain percentage?

If a trace is designed to be 50 ohms, how much of an effect would 10% or 20% mismatch between line impedance and termination values ? For instance, a 50 ohm line with 45 ohm or 55 ohm series ...
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2answers
105 views

Trace termination length limits

Are there any length limits to series termination ? If I have a trace that's 12 in or a trace that is 100 in, can the same series termination resistor be used (assuming that Zo = 50 ohm) ?
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3answers
103 views

How to select source termination resistors by looking at signal?

If I have two devices that some distance apart on a fairly large PCB (could be 1 in, or it could be 20 in). If I arbitrary select a value for R1, lets say 33 ohms in this example and if my digital ...
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2answers
482 views

Why is Bob Smith termination for Ethernet recommended if it's wrong?

I came across this article today (more detailed paper), which claims that the widely recommended Bob Smith termination (75-ohm resistor + 1000pF to chassis GND) may not be ideal (or correct). If this ...
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4answers
565 views

What are the main causes of Overshoot and undershoot of a signal?

I'm not an EE major, but I was curious what causes overshoot and undershoot. Where can i find a detailed explanation of the process? I heard it has to do with the parasitic capacitance, but there ...
1
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2answers
175 views

Causes of ringing in a PCB

Im trying to understand the source of ringing at the termination point of a PCB traces before i delve into actually designing a PCB. For example, by 'termination point', I mean a clock signal ...
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1answer
65 views

Termination of digital lines

So when exactly is termination of a digital signal required? In my case, I'm dealing with a 1.8V signal that comes from an FPGA. This signal connects to a high impedance input of an OpAmp. The trace ...
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votes
5answers
866 views

Most ideal wire termination for round screw terminals

My '60 Volkswagen Beetle uses a number of electrical components that are equipped with round screw terminals, like you can see in the picture below: What is the most ideal wire termination for ...
0
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1answer
60 views

Cable screen terminations for enclosure containing SMPS and instrumentation signal conditioners

I'm looking for some help with some screening and cable termination decisions I need to make. I'd be grateful for any advice, and I'll do my best to explain myself clearly. I am building a control ...
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1answer
111 views

Termination resistors in Ethernet in Kilo-Ohms instead of Ohms?

When working with Ethernet, whether copper or optical fiber, why are the termination resistors always in a few ohms and never in kilo-ohms? Example: 49.9R on transmit & receive pair of PHY in ...
0
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0answers
58 views

series termination resistors for SPI communication

I am designing a PCB where I have the PIC18F26J50 interfaced to the MRF89XAM9A through SPI. This would be an on-board communication. Do I need to add series termination resistors to match trace ...
2
votes
1answer
114 views

Alternative to high Watt resistor terminating resistor

In the following circuit a 120 ohm termination resistor is placed across the Rx+ and Rx- data lines connected to a RS485/422 transceiver. The transceiver is protected up +/- 60V. simulate this ...
2
votes
2answers
126 views

Very long transmission-line design tips

I'm designing a very long transmission line between a master node a some slaves far away connected by a bus where only 3 wires are used: - A DC power supply (24vdc) - B Digital comm - C Ground As ...
6
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1answer
914 views

Bob Smith Termination with POE

I'm looking into doing a Bob Smith termination for a Power over Ethernet (POE) PSE. The TI app note shows the following termination: But all of TI's reference designs (and later figures in the same ...
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1answer
94 views

Terminating SDRAM on opposite side of board

I have a 4-layer board with the micro and sdram on opposite sides, the ram signals are short, but I still want to terminate them (I can test the board later and determine if I really need ...
1
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3answers
931 views

Load Resistor across Crystal

What is the purpose of using a 1M Ohm resistor across crystal pins? Please refer to the image for clarity. The crystal serves as the clock source for an USB Hub device(LAN9512). There is nothing ...
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5answers
302 views

Use transistor to connect terminating resistor for differential signal?

Is it okay to use a transistor to connect a terminating resistor between the A and B lines of a differential signal? I'm not sure because I know that at the source/emitter of an NPN transistor must be ...
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1answer
64 views

What is digital Termination and when is it used?

I have heard transmission line termination but today I came across this "Digital termination" but couldn't find out why is it used and what effect does it have on digital signals?
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5answers
772 views

How to use input/output termination resistors in filters?

NOTICE: I have added another question here that a solution for each one may help for solving the other one. Please look at Fig-1 below. It is a common usage of termination resistors. R1 , R2 work ...
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1answer
122 views

USB data lines: current consumption

I am designing a USB device and I can't find easily the USB specs about the maximum current consumption allowed for the D+ and D- lines. I am planning to use a 39Ω termination resistor on this ...
3
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2answers
473 views

SPI multiple slave termination

I've been reading about signal integrity and went through this site reading about it as well as other references. Alot of the topics deal with a single slave, but not so much multiple slaves. I'll be ...
2
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2answers
403 views

HD-SDI serial data output termination

Soo.. I've been testing my designing limits, trying to learn about Serial Digital Interface, and building a simple reclocker with TI IC's. And now I've run into a small speedbump with the output from ...
3
votes
1answer
355 views

USB Termination Resistor

I am using the Atmel AVR32 UC3C AT32UC3C2512C for a project and the datasheet doesn't say anything about terminating the USB connection, but the AVR32768 Application note, clearly points out a 39 ohm ...
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votes
2answers
803 views

What is the importance of the \$50\Omega\$ resistors in this RF op-amp circuit?

From the TI application note RF and IF amplifiers with op amps: The source says "The 39-pF capacitor provides peaking to compensate for some high-frequency roll-off, but better IP3 performance can ...
3
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1answer
2k views

How do different methods of transmission line termination compare?

It seems to me that there are three ways to terminate a transmission line: at both ends at the load only at the source only simulate this circuit – Schematic created using CircuitLab ...
2
votes
2answers
438 views

Do I need to terminate extremely short traces (< 0.5 inches)?

Some background: I have a little hobby project running that basically interfaces a 64 pin ARM mcu (the STM32F405RGT6) to a stereo codec (a TI PCM3010) via I2S interface. I'm deriving the master clock ...
7
votes
2answers
1k views

CAN Transmission and termination resistors

I have been trying to set up a CAN network using PIC18F25K80 microcontrollers and an MCP2551 to communicate between them. Can I use two simple wires as a CAN bus by just connecting the CANL, CANH of ...
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1answer
445 views

Simulation software to terminate planar waveguides by geometry and material choice?

There are a lot of electromagnetics software modeling suites out there (HFSS, CST Microwave, Sonnet some I've heard of). I want to terminate a coplanar GS or GSG waveguide with 50 ohm. I know that ...
3
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1answer
1k views

How to terminate a coplanar waveguide with 50 ohm load?

So I want to structure a coplanar waveguide by lithography, VNA - coaxial - picoprobe - coplanar waveguide transition to measure impedance of the waveguide. As signal and ground lines are on one ...
3
votes
1answer
250 views

Coax cable with CAN bus

I got some Microchip CAN transceivers and some Stellaris Launchpads from TI. I would like to learn how CAN works. It looks very nice for what I want to do (one controller per room, controls lights, ...
17
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3answers
25k views

Why does the CAN bus use a 120 ohm resistor as the terminating resistor and not any other value?

I know the reasons for using terminating resistors on a CAN bus and how important it is. But why 120 ohm? How did this value come up? Is there any specific reason to use 120 ohm?
5
votes
3answers
2k views

Is there a preferred placement of termination resistor for a differential clock line?

Looking at a reference design board from Xilinx, we noticed the placement of the termination resistor for a differential clock line (~300 MHz): The resistor is placed not at the closest possible ...
0
votes
1answer
461 views

How to determine the value of termination resistor?

How to determine the value of the termination resistor? Is the termination resistor used to reduce the reflection of the signals and also have to match with the transmission impedance? How am I going ...
16
votes
2answers
4k views

Termination resistors: are they needed?

For a project I'm designing, I'm using an IS42s32800 (TSOP) SDRAM with an LPC1788 (QFP) microcontroller. On the PCB I have 4 layers with a ground plane right below the top signal layer and a VDD plane ...
12
votes
3answers
11k views

SPI Bus Termination Considerations

So, in my previous question I asked about using the SPI bus over short distance for board to board communication. I was recommended to try termination resistors. I placed a resistor close to the ...
7
votes
3answers
3k views

At what cable lengths are termination resistors required for RS-485 networks?

I've noticed my experiments in the lab with RS-485 work fine with fairly short cables, but termination resistors are needed for true installations. Is their presence or absence a function of the ...
2
votes
2answers
568 views

How do I use directional couplers on a differential signal?

I understand how a directional coupler can be used to measure signals travelling in one direction on a wire. What I don't understand is exactly how this would work on a differential signal, E.G. LVDS ...
4
votes
2answers
447 views

Why does the ISDN S0-Bus require terminating resistors?

It is a well-known fact that ISDN S0-Bus must be terminated with 100ohm resistors to match the transmission line. This is the case even for everyday household installation with cable runs shorter than ...
2
votes
1answer
654 views

Terminating Transmission Lines with a Resistor

I have a large, but slow, SPI bus comprising of 8 devices. The frequency of operation is 2 MHz. As I understand, I need to ensure that the bus lines are properly terminated or reflections may cause ...
11
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3answers
719 views

Measuring impedance

I am designing and building circuits which use 100Mb/s on a Low Voltage Differential Signaling (LVDS) bus. Some of these signals need to travel between PCBs on hand made cables. The problem is that I ...