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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Do I need to measure impedance before every CAN termination?

Background: I need to set up a CAN bus between different components of an electric UAV (battery management system, motor inverter, autopilot, etc.). My avionics/networking experience up to now ...
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55 views

USB 2.0 termination. Single ended vs Differential

why are usb 2.0 differential traces terminated with 45ohms each to ground, instead of being terminated with a 90ohm resistor across the pair? and if it is equivalent, why would we choose one way over ...
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38 views

Unexplained differences in behaviour between U.FL-terminated antenna and SMA-terminated antenna

I would like your opinions/advice regarding an unexplained observation between a U.FL-terminated antenna and an SMA-terminated antenna. Both antennas are from the same manufacturer and normally tuned ...
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1answer
44 views

How would I place CAN termination resistors in a 3 ended configuration?

I have a project for which I have one central circuit board which has a can node on it, this central circuit board has three connectors on each of which a node could or could not be plugged in with a ...
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49 views

How to properly terminate this circuit

I have a 50 ohm BNC cable which connects to a coaxial connector on a PCB. I want to invert the signal from the cable with an op amp. If I use the top circuit from the image, will the cable be ...
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46 views

On-PCB SPI Distance Considerations

I've been reading about ringing and overshooting and all sorts of things, but all without getting a real "feeling" for how likely these things are to affect my circuit. I've got a chip generating an ...
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1answer
27 views

SN65HVD3x (RS485 Driver) - Termination resistor

I want to use the SN65HVD31DR to connect two microcontrollers together. The connecting cable has an impedance of Z0 = 80Ω. According to the data sheet it is recommended to terminate the connection ...
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1answer
397 views

The CAN bus in this vehicle has only one 120 ohm termination resistance. What problems would this provoke?

This vehicle that I've started co-developing is designed with only a 120 termination resistor on the CAN bus. Obviously there should be two of those resistors on two ends of the bus. I will be making ...
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165 views

Common mode choke parameters CAN circuitry - split termination concept

I am trying to the understand the important parameters of a common mode choke that will be placed at the CANL and CANH lines of a transceiver. First parameter: Impedance as function of frequency - I'...
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1answer
69 views

analog signal generator output in Volts vs dBm

I am connecting a mixer to a microwave source and need to be careful of how much power I am giving to the LO and RF of the mixer. If I just stay in the unit of dBm, it would be ok but I became ...
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2answers
83 views

RS485 termination

What is the recommended way for termination RS485? I read about couple of options to do this. If I don't want to do dissipate extra power, can I just put 120 Ohm resistor? I saw the follow ...
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3answers
234 views

How far can a terminating resistor be from the literal end of a CAN bus?

I'm wondering if anyone knows if there is an upper limit for the distance a terminating resistor can be from the literal end of the CAN bus or where the last node is. We have an HMI that is connected ...
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45 views

Terminating Unidirectional Differential Signal

In a project I'm working on, I'm planning to use the SN75174 to send a signal through about 30m of twisted pair. This signal has a bitrate of around 1Mbps (it's a signal to drive WS2811 LEDs,) and ...
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1answer
65 views

Power over ethernet and common-mode termination

I have a non-standard Power over Ethernet application (connector, and devices are not ethernet standard but we are using ethernet pairs and protocol for communications). On looking at PoE schematics I ...
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1answer
425 views

SPI bus multi-slave termination

I have been using a Tiva C microcontroller (TM4C1294NCPDT) as master to communicate with 6 SPI devices (slaves). The SPI clock is 8 MHz with 1.5 ns rise time. My idea is depicted bellow. My design do ...
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69 views

How does the data rate of a CAN bus affect the value of the capacitor used in a split termination scheme?

I'm helping to redesign the CAN bus of an electric car, and we're interested in achieving higher data rates of up to 8 Mbit/s. We have a transceiver selected, a CMC to reduce inductively coupled ...
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1answer
328 views

Should I terminate the MII/RMII interfaces?

For Ethernet PHY design, the MDI interface should be terminated. Then how about the MII/RMII or GMII/RGMII interfaces? I've seen some designs terminated them, and most not. There are some PHY chips ...
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1answer
192 views

Terminator in Raspberry Pi CAN-shield

I am planning to connect (at least) two Raspberry Pi + PiCAN2 shields via CAN. I think I understand the concept of a daisy-chained multidrop CAN line, but what about using the 120 ohm resistors for ...
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136 views

Impedance for TTL Hsync and Vsync Pulses

I'm just finishing up a sync combiner and audio/video PCB. I'm trying to impedance match my traces and I've done so for the 75 ohm RGB lines. Now I'm looking at the TTL level Hsync and Vsync lines ...
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179 views

DDR2 and DDR3 ODT and ZQ calibration

Can anyone please explain what is the difference in ODT and ZQ technique used in DDR2 and DDR3?? Which method is very useful for DDR2 termination? whether ODT or External parallel termination?? ...
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84 views

Name of PCB termination

Whoever knows how that circle terminations called (part number)?
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76 views

Series Termination value is very large

I am budding engineer working on RE testing. I know about series termination. We are using 50 ohm as trace impedance. We are getting large reflection and emission in SD clock. I used series resistor ...
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2answers
511 views

rs422/485 maximum terminator resistor value

as i know terminator resistor value is ~120ohm. But i found a circuit that has 10kohm terminator resitor at A and B lines. In circuit transeiver IC is SP3485E. What is the reason for 10k ? That is ...
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70 views

CAN bus cable-termination mismatch

I am trying to change the CAN cables alone to Cat 6 cables (which has 100 ohm characteristic impedance). The existing cable has 120 ohm impedance. By making this change to Cat 6 cables, I am ...
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1answer
101 views

Terminating unused inputs and outputs

At >5 GHz RF rates, stray inductance and capacitance found inside 0402 resistors and capacitors play a not-insignificant role. I'm trying to work thru, then, if a 50 ohm AC termination at the end of ...
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302 views

Is signal reflection dependent to PCB track length?

We add a termination resistor at the end of a transmission line in order to prevent its signal from reflecting back. I have deduced from some discussions that the termination resistor is not necessary ...
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3answers
824 views

With parallel termination of a transmission line, why does the receiver see the full voltage?

With parallel termination of a transmission line, the line characteristic impedance \$Z0\$ is matched with the pull-down resistance \$Rt\$. But, in that case, shouldn't the receiver see half of the ...
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1answer
131 views

Termination for backplane

I'm developing on a small modular computer system using the Z80 just for fun. The backplane is a prototype PCB with five DIN41612 connectors wired in parallel, running about six inches from the first ...
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2answers
976 views

Serial resistance for SPI bus (33 ohms, 50 ohms…)

I have a question about SPI communication. I learnt that we should place a 33 or 50 ohms serial resistance in MOSI/MISO lines for the adaption, and overshot. My question is how could we find these ...
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1answer
688 views

J1939 ,9pin Deutsch diagnostic connector [closed]

I am a novice,in this area Sorry!I have no communication/ connection to a excavator as in the above title My later model machine I can connect no problems. Between the pins for Can High and Can low I ...
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1answer
183 views

Check of my first Eagle boards

I am attaching two boards I have just designed in Eagle and would appreciate if any expert around here willing to take a quick look would flag any obvious errors in the design. There is one board ...
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1answer
797 views

Why is the signal amplitude low on the oscilloscope even though the impedance is matched?

I have a photodetector with differential outputs that are each 50-ohm terminated. When I connect one output to the oscilloscope to look at the signal, I see a higher signal amplitude with higher ...
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1answer
50 views

SoC Digital Output Rise Time

I'm interested in calculating series termination resistors for my communication lines for a system I'm designing based on the Zynq-7000 SoC. The system runs on a 33 MHz clock but I'm sure the ...
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2answers
143 views

Feeding multiple 50 ohm terminated outputs from a single 50 ohm source without signal degradation

I'm having an issue in which I have a trigger from an instrument meant to be sent to another instrument with a 50 ohm termination. I want to use that signal to distribute it to several outputs that ...
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1answer
3k views

Calculating series resistors for I2C/SPI lines to reduce EMI and ringing

How do you determine if a series resistor is needed for I/O lines, and what value is needed? Where should the series resistor be placed? My assumption is the resistor should be placed as close to the ...
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3answers
256 views

Series Termination Resistors Sharing a Common Point

Suppose I have a high speed digital signal (represented as a square wave) that splits off and is shared between two subsequent inputs stages (represented as MOSFETs). Is it better to have two series ...
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4answers
975 views

Transmission line and termination and input impedance

I'm confused why sometimes when we look at the termination effect on a transmission line, we don't consider the overall input impedance looking into the transmission line including the load? For ...
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1answer
439 views

Correct SPI, I2C termination and EMI limiter for external bus?

[EDIT] This question has been edited. The bus does not split anymore. The entire question and figures has been edited. BACKGROUND I'm using an ATSAM3U2E and want to include both the SPI and I2C bus ...
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1answer
2k views

How many (m)W should 120 ohm CAN bus terminators have?

When I started with Arduino I bought a set of 600 resistors (30 times 20 values). However, I found out 120 ohm needed for CAN bus is not among them. So I need to buy 120 ohm resistors (I don't want ...
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3answers
1k views

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 ...
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2answers
166 views

Interfacing an LVDS driver with an LVPECL receiver

I'm trying to understand how the below circuit allows interfacing LVDS levels with LVPECL levels. Assuming: Driver: Voh = 1.4V, Vol = 1V, Vcm = 1.2V Receiver: VBB = 2V After the transmission ...
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1answer
213 views

BNC cable to composite video cable conversion

I currently have a robotic cutter which has a BNC female connector connected to a composite video cable. I want to remove this extension cable and simply terminate the cable to a composite video ...
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3answers
82 views

Under which circumstances would CAN communication still work if there is no bus termination?

The bus termination is needed to prevent reflections. Does this mean that it may be possible to get a working communication with a low data rate, since then reflections might not interfere with the ...
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2answers
780 views

Termination on Ethernet line with Magnetics

I'm trying to understand this schematic: The ethernet lines end in a device with the input already 100 ohm terminated. The magnetics have a ratio 1CT:1 so the input of the rj45 Connector should have ...
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1answer
233 views

Should I remove terminating resistors in ethernet TAP?

I would like to design Ethernet TAP, with PHY, that I can connect to FPGA via RGMII interface. I know, that I could do this like there, but I would like to be able to analyze low level data in MAC. ...
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2answers
384 views

DDR3 Series Termination Length Matching

I am implementing a DDR3 interface on a PCB and I have a question regarding the termination of address/control/command/clk traces. I have series terminations for all the required traces mentioned ...
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2answers
409 views

I2S - Ribbon Cable - Termination

I have 2 boards connected via a ribbon cable. CPU board is an 3.3v ARM providing the I2S signals(bit clk, data, L/R signal). I'm using 44100 - 16 bit audio so the bit clock is just approx 1.4 mhz. ...
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454 views

How to design DDR3 PCB without any termination resistor in processor and RAM connection

As I'm going to design my first high-speed PCB, I'm confused with some mismatches between what i see in high-speed PCB design tutorials and what i see in real world designs. in the PCB handbook named "...
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4answers
2k views

Does it matter which 2 nodes on a CAN bus you terminate?

I know you need to terminate the 'ends' on a high speed CAN bus but what if you know nothing about the topology of the network or where the bus will go. For my application i have designed a data ...
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1answer
2k views

Proper CAN bus termination

I've been struggling with getting CAN bus transmission to work properly. I'm driving the setup with a Parallax Propeller board and the specifics are in another post, but I have a more specific ...