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.

Filter by
Sorted by
Tagged with
0
votes
2answers
70 views

Oscilloscope amplitude reading depends on cable length? Reflection help

Suppose I have an RF source with 50 Ohm output impedance. First lets imagine the RF source outputs a low frequency 10 kHz signal (electrical wavelength is about 20 km). Suppose I have a 50 ohm coax ...
1
vote
1answer
35 views

CAN Split Termination Capacitor Calculation

I'm trying to use the split termination on a CAN bus, but I'm a bit confused about the calculation for the split termination capacitor. It is described in Figure 10 in the Texas Instruments app note ...
1
vote
1answer
62 views

No terminations on point to point DDR3?

Are terminations required for DDR3 in point to point designs? I saw a reference design that doesn't include any termination to VTT for a controller/single DRAM design (pt to pt). DQS, DM and DQ use ...
0
votes
2answers
30 views

RS485 slew rate limiting remove need for termination

In regards to the highlighted feature of "slew-rate limiting" RS485 ICs. It says in multiple brand datasheets that the slew-rate limiting helps with transmission errors when there is ...
0
votes
1answer
48 views

Terminal resistor function on JTAG SMT2 schematic

I'm studying the Digilent JTAG-SMT2 datasheet, in particular the schematic of Example 3 (Interfacing a Zynq-7000 while retaining the Xilinx JTAG Header). I have a doubt about the function and value ...
0
votes
2answers
52 views

Unused output of LTC6957-4 (or LTC6957-3)

The LTC6957-4 has two complementary CMOS outputs, and I only need one. What do I do with the unused output? My goal is to minimize noise on the used output signal, REFCLK_OUT. The datasheet is clear ...
0
votes
2answers
102 views

Selectable CAN bus split termination

I am designing a CAN device where the user may switch between it being the end device and thus with terminators or vice versa. Now, there is no need to drive it digitally using MCU, I would actually ...
0
votes
0answers
223 views

RS485 Pull-up, Pull-down and single termination resistor

Currently I use for Modbus RTU via RS485 with a shielded cable length of about 5 meters and a bitrate of 19.200 bit/s. Wired are 680 Ohm pull-up (A->+5V) and pull-down (B->GND) resistors near to the ...
0
votes
1answer
70 views

Does the standard termination of 120 ohm really suppress reflections in recessive state in CAN?

Suppose we have a multi-node CAN network with the ends of transmission line terminated with the standard 120 ohm. When the recessive state is on the transmission line, the voltage on both CAN_H and ...
1
vote
1answer
200 views

Terminating Resistors on Ethernet Port

I'm using Ethernet (CAT5/5e/6) cables to communicate with the PCA9615 Differential I2C buffer. These cables roughly have a characteristic impedance of 100 ohms, but I have a few questions about ...
1
vote
0answers
57 views

Need to branch USB data lines… what to do with unused ends?

I have a USB 2.0 low-speed connection design with an unusual constraint. On the host side the D+ and D- lines have a branch, a requirement of the connector and this cannot be changed. On the device ...
0
votes
1answer
43 views

What if ddr4 Termination is done at last word component

Memory Component : MT40A256M16 Controller : Xilinx MPSOC - PS Side Question : I have mistakenly provided the DDR4 termination resistances at the first data lane and the layout engineer has completed ...
0
votes
0answers
40 views

What's the best way to terminate an unconnected composite video cable from a “pass-through” monitor output?

I have a Sony PVM-9045Q¹ video monitor with composite video inputs that have a "loop-through" output for each input. The outputs are described as "75 ohms terminated (75 ohms automatic termination)," ...
0
votes
1answer
33 views

Can capacitors be used to make a low-impedance ECL termination voltage?

I am trying to develop a circuit in which an RF sinusoid is put into the input of the ADCMP552 PECL output comparator and then the PECL output (square wave ish) is input to the MC100EP140 phase ...
0
votes
1answer
66 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 ...
0
votes
4answers
533 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 ...
1
vote
1answer
103 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 ...
3
votes
2answers
185 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, ...
0
votes
1answer
80 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 ...
11
votes
4answers
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 ...
0
votes
1answer
201 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 ...
0
votes
0answers
34 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.
1
vote
2answers
91 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. ...
3
votes
0answers
67 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 ...
0
votes
1answer
58 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 ...
1
vote
2answers
56 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 ...
2
votes
1answer
109 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. ...
1
vote
0answers
80 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 ...
0
votes
2answers
285 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 ...
2
votes
1answer
130 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 ...
2
votes
3answers
225 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 ...
1
vote
2answers
122 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 ...
1
vote
0answers
117 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 ...
0
votes
1answer
64 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 ...
1
vote
1answer
362 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 ...
0
votes
0answers
57 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 ...
2
votes
1answer
169 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 ...
1
vote
1answer
58 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 ...
0
votes
1answer
93 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 ...
0
votes
1answer
43 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 ...
2
votes
1answer
2k 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 ...
1
vote
1answer
599 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'...
0
votes
1answer
195 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 ...
2
votes
2answers
391 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 ...
2
votes
3answers
566 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 ...
2
votes
1answer
140 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 ...
3
votes
1answer
1k 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 ...
1
vote
0answers
174 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 ...
4
votes
1answer
572 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 ...
2
votes
1answer
315 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 ...