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.

learn more… | top users | synonyms

0
votes
1answer
29 views

DDR2 ODT pulled low

I was looking at a DDR2 design that had it's ODT pin pulled low, presumably this was done because the CPU doesn't have and ODT pin. Reading the datasheet though I don't see a clear explanation of ...
1
vote
1answer
79 views

CAN network resistor termination [duplicate]

My question is about the resistor for termination in a CAN network. From an electrical perspective why should we add this resistor (commonly 120 Ohm) between the CAN_H and CAN_L? Thanks in advance.
2
votes
3answers
108 views

How to terminate switching transistor for level change?

For a typical driver, I would add a series termination resistor to terminate the line. But what would be the correct way to terminate when a transistor is used to level shift a 3.3V/5V signal to some ...
1
vote
1answer
90 views

Termination of unused PoE pairs

How important are the specific termination values used for PoE pairs (pins 4&5, 7&8)? Below is the recommended Ethernet front end for Micrel’s KSZ8841/42. ...
4
votes
1answer
136 views

USB hub and slave on same pcb - are serial resistors and capacitors needed?

I'm building a device using TUSB2046B hub controller 4x FT230X USB to UART controller First, let's look on Hub controller sample application: Note D: All USB DP, DM signal pairs require ...
1
vote
0answers
50 views

Clock signal sharpness

I'm currently tuning the termination resistors in the clock circuit. The resistor here is 330 ohms, I got a rippled clock signal like this: I increased both resistors value to 430 ohms and I got: ...
1
vote
3answers
263 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 ...
2
votes
1answer
167 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
votes
1answer
555 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 ...
1
vote
1answer
171 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 ...
1
vote
1answer
507 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 ...
1
vote
1answer
126 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
votes
1answer
213 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 ...
1
vote
0answers
96 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 ...
16
votes
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
0
votes
1answer
62 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 ...
0
votes
2answers
189 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) ?
1
vote
3answers
199 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 ...
4
votes
2answers
2k 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 ...
0
votes
4answers
2k 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 ...
2
votes
2answers
421 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 ...
0
votes
1answer
81 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 ...
5
votes
5answers
1k 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
votes
1answer
92 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 ...
0
votes
1answer
137 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 ...
2
votes
1answer
167 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
142 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
votes
1answer
1k 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 ...
1
vote
1answer
112 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 ...
2
votes
3answers
1k 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 ...
0
votes
5answers
507 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 ...
1
vote
1answer
74 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?
3
votes
5answers
1k 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 ...
1
vote
1answer
127 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
votes
2answers
628 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
votes
2answers
536 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
414 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 ...
7
votes
2answers
1k 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
votes
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
502 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 ...
8
votes
2answers
2k 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 ...
0
votes
1answer
523 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
votes
1answer
2k 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
278 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, ...
19
votes
3answers
34k 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
533 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
5k 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 ...
14
votes
4answers
14k 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
5k 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 ...