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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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1answer
32 views

Terminating bidirectional data lines and clock for memory-mapped devices

I am wiring up an STM32H743 to an SRAM or an FPGA to memory map it (i.e. I would like to be able to re-use the schematic). This SRAM operates at a maximum of 50MHz. The FPGA can operate at 50MHz all ...
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106 views

RS422, RS485 Termination Resistors

While going through this youtube video from TI about the RS232, RS422, RS485 differences. One thing that don't understand clearly is following slide from this video. The blue resistors that I marked ...
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1answer
85 views

Series termination on receiver side?

I'm new to signal processing and have a specific question about a PCB design by TI. (TDC7200EVM User’s Guide ) (TDC7200EVM) Could anyone explain why they place the series terminating resistors on the ...
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112 views

How to properly terminate this circuit (50ohm coaxial to oscilloscope)

I'm a bit confused how this type of circuit should be terminated. I have no experience with transmission lines, so I do not know where to put 50ohm resistor. It's basically output from opamp, ...
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33 views

CAN BUS Termination Resistors For CAN Logger Device

I am making a CAN logger device that will be connected to the vehicle OBD port. Since the CAN bus inside the vehicle is already terminated, do I need to terminate the BUS lines on my device end, right ...
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2k views

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 ...
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1answer
77 views

Is this a reasonable setup for terminating and protecting an RS-485 transciever?

I'm working on a design where an RS-485 transceiver IC is connected to a Cat5e cable, hopefully at 96k baud at a distance of up to 150m. I'd like to offer some protection in the design, but I've never ...
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33 views

Do I need to include another set of termination resistors? (design specific)

I am including an ethernet pass through in a design. I am wondering if I need to include more termination resistors on the second(left) RJ45.
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2answers
53 views

Ringing problems on the output of inverter/comparator

I'm trying to drive some RF switches that need 0 to -5 V control logic with a 0 to 3.3 V signal. I found 2 topologies for this level shifting effect, one using a comparator and one using an inverter. ...
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65 views

Eliminate reflections on pulse signal transformer

I am trying to isolate an RLC ringdown signal via an RF signal transformer but I'm having trouble maintaining the signal integrity through the transformer. Below is the simple schematic describing my ...
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1answer
55 views

Is current direction always opposing when signals are reflected on a transmission line

Having read Dave Tweeds excellent description of reflections in electrical transmission lines, I thought I was one step closer to a full understanding of SWR. However, later I was watching w2aew's ...
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2answers
46 views

Pulse Down a line with Series terminations between transmission lines

I am interested in a relative edge case in transmission line of a simulation. If send a pulse down the setup below, now obviously my rudimentary steady state electronics knows this is a basic voltage ...
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1answer
47 views

Multiple Terminating Resistors on RS-485 Bus

I bought this TTL to RS-85 board and before connecting it to my Arduino I decided to double check (reverse-engineer) its circuit and I can see there's a 120 ohm resistor between the A and B outputs. ...
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53 views

Selecting VTT termination resistors

I'm interfacing two 8-bit DDR3L DRAM ICs with an NXP LS1012A and I decided to go with a fly-by topology. So, I need to terminate the address/command/control and clock signals to VTT (in parallel). But ...
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2answers
132 views

Should I remove the termination resistor from the CAN Bus transceiver module?

I develop a CAN-BUS receiver (logger) with an ESP32 and CAN-BUS transceiver. The CAN-BUS transceiver modules which I found and bought have both 120 Ohm termination resistors. But the CAN-BUS to which ...
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1answer
79 views

Reducing EMC from a long trace where one end is normally floating

Following on from this question about a PCB layout with EMC issues, I'm currently reworking the design to minimise breaks in the ground plane and try and identify any other EMC issues. One thing that ...
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3answers
141 views

CAN Physical Layer With Different Characteristic Impedance

The company I have been working for, which is designing a new control system for forestry equipment, has encountered a number of problems with regards to the CAN bus it is using for communication. I ...
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2answers
82 views

Termination between driver and transceiver

I have the following line driver and line transceiver driver: 74VHC244 transceiver: 74VHC245 They're connected via a 0.5m long ribbon cable with an impedance of 100Ohm. The digital signals have a ...
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70 views

Thevenin Termination Current Calculation and Iol/Ioh

I am calculating the current draw for a thevenin termination and am having issues with the Iol and Ioh from the datasheet. From my understanding, when the source goes high (Voh), then Vtt (dest input ...
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1answer
57 views

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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1answer
170 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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44 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
94 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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1answer
53 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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1answer
75 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
36 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
990 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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1answer
367 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
140 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
199 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
375 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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1answer
102 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
744 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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124 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
447 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
275 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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179 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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0answers
229 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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86 views

Name of PCB termination

Whoever knows how that circle terminations called (part number)?
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1answer
134 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
845 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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1answer
75 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
124 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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3answers
390 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
1k 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
164 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
2k 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
1k 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
206 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
898 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 ...