Tagged Questions

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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2
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1answer
70 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
104 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 ...
5
votes
1answer
106 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
53 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
vote
3answers
302 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
146 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
57 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?
0
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0answers
34 views

Where does Vcc-2 comes from in ECL. Is it the max requirement of spec to keep the BJTs in ECL in active mode all the time? or is it something else?

In ECL logic devices, what is Vcc-2 voltage you usually terminate with? I mean where does Vcc-2 comes from. Is it the max requirement of spec to keep the BJTs in ECL in active mode all the time? or is ...
3
votes
5answers
502 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
116 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
345 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
246 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
239 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 ...
6
votes
2answers
578 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 ...
2
votes
1answer
824 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 ...
0
votes
2answers
293 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 ...
5
votes
2answers
829 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
304 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
949 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
192 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, ...
14
votes
2answers
14k 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
1k 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
295 views

determine the value of termination resistor

How to determine the value of the termination resistor ? the termination resistor is used to reduce the reflection of the signals and also have to match with the transmission impedance? How am I going ...
15
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2answers
3k 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 ...
8
votes
3answers
7k 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 ...
4
votes
3answers
2k 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
473 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
396 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
512 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
votes
3answers
620 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 ...
1
vote
1answer
184 views

HCMOS drivers impedance table

I wonder, is there a table somewhere where I can find out impedance of drivers of various HCMOS series? I am specifically interested in AC, ACT, LVC and HC series. I guess input impedance is very ...
1
vote
1answer
141 views

How to make a SCSI-3 terminator?

I have an old VAXstation that has an external SCSI Bus. When I don't have anything attached to that, I get errors. I was thinking of adding a terminator, but those that I found online are quite ...
2
votes
2answers
398 views

DDR2-SDRAM Termination methods: passive vs. active

for a project I'm designing I am currently using a simple parallel Resistor Termination on the DDR2-Traces. But I'm wondering, what is the advantage of using a voltage regulator with ...
13
votes
5answers
17k views

How termination resistors work; what happens if I use lower values?

I am going to try to interface low-speed 8bit DDR2 chip to FPGA, and I've got some questions crucial to make it work :-) Is that correct that the idea of termination resistor is to sink most of the ...
3
votes
1answer
317 views

Do DDR2 chips and controllers have on-die termination?

I am going to try to interface a low-speed 8-bit DDR2 chip with an FPGA, and I've got some questions crucial to make it work: Is that correct that there is on-die termination on both DDR2 memory and ...