Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [termination]

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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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?
Swanand
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SPI bus termination considerations

So, in my previous question I asked about using the SPI bus over a short distance for board to board communication. I was recommended to try termination resistors. I placed a resistor close to the destination (but not exactly there, there was a…
Saad
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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 signal to GND, so that only small part of it…
BarsMonster
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SDRAM 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 right above the bottom signal layer. Average…
ozg
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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
sumeet
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SPI bus termination and pull-up resistors

My microcontroller (ATMEL series) needs to communicate to a slave device using SPI protocol. I am designing the hardware. The maximum SPI bus speed is 1 MHz. The distance between the master and slave is less than 50mm. Q1) Do I need to add…
Bharav
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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 cable length, or other factors?
fred basset
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Can we reduce power consumption of digital interfaces by using high impedance transmission lines?

Transmission lines must be terminated with the same impedance as the transmission line has itself to get an impedance matching and avoid reflections at a high impedance end point. This termination resistance closes the current loop between two…
jusaca
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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 have no way of verifying the quality of the…
Rocketmagnet
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Are special terminals required for connecting thermocouple wires to a PCB?

I'm currently trying to integrate a type K thermocouple into an electronics project. I intend on interfacing this thermocouple with the MAX31855 cold-junction compensated thermocouple-to-digital converter IC. I am not an expert on thermocouples and…
Izzo
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SPI bus connections - to loop or not to loop?

I have a question regarding the physical connection of an SPI bus. I have an SPI master (a PIC32 device) and a number of slaves (in this case PIC16 devices). I'm only writing to the slaves, and the protocol takes care of which one does what when, so…
Roger Rowland
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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 is the case, why is Bob Smith termination still…
cdwilson
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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 document) use the following termination with two…
aghoras
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RS485 termination: AC + failsafe + parallel + bidirectional

Knowing that I need to refine my RS485 circuitry, I've been reading. I have a series of specific questions and I hope that you'll indulge me as I describe how I attempted to follow through an application note. Here are some basics of the serial comm…
Reinderien
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USB trace impedance calculations, with termination resistors

I'm designing a PCB featuring a Renesas RZ-A1 microcontroller, and want to check that I'm doing my USB D+ and D- traces correctly. This application note from Fairchild (alternative link), which is one of the top Google results, says that D+ and D-…
beammy
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