# 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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### SPI device stops working when integrating Schmitt triggers and ESD diodes

I am integrating a BME680 temperature, pressure and humidity sensor using SPI. When I only use 33 Ohms series resistors, the system works fine. However, when adding Schmitt triggers (NL27WZ17DFT2G), ...
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### Add or remove 120 Ohm from the CAN circuit using Microcontroller

I want to design hardware circuit using microcontroller for CAN communication. One suggestion i require is i want to add 120 Ohm or remove it based on software configuration. I want to close the ...
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### How can I measure a 100 MHz signal with unknown source impedance with an oscilloscope?

As a part of a device I designed, I have to measure multiple higher frequency square wave (and sinusodial) signals with unkown source impedance. The intended signal path is shown in the picture: My ...
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1 vote
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### 24MHz Clock Signal Distortion

I am measuring a 3.3 V 24.576 MHz clock signal coming from a CDCE913. The signal is used to drive 25 audio TDM receivers. The line is terminated in series with a 33 ohm resistor at the transmitter end ...
1 vote
57 views

### Thevenin Termination - Calculating $I_{OH}$

I am trying to see if my driver can drive the following circuit. The spec for the driver is $V_{OH,min} = 1.62 V$ and $V_{OL,max} = 0.18 V$ at $I_{OH}/I_{OL} = +/-4 mA$. So the $V_T = 0.9V$ ...
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### Should unused connector terminals be connected to ground?

I am using both male and female D-SUB connectors and about half their terminals are currently unassigned, unused and unterminated. They are not the crimpable versions, all the conductive terminals are ...
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### CAN BUS Termination resistor sizing

I am using ISO1042 CAN Transceiver to establish communication between my board micro-controller with other board controller separated by 0.5m distance. I am using standard 120 ohm termination ...
1 vote
135 views

### GPIO controlled CAN bus termination technique

I have tried to design a circuit for controlling the CAN bus 120 Ohms termination resistance by using a 3.3V GPIO from a STM32 MCU. In the SSR datasheet, it specifies that the LED voltage should ...
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### Should long PCB traces be treated as transmission lines?

Suppose I have a BNC in connector, terminated in parallel with a 50 ohm resistor. The PCB trace extends for about 5-7cm before the signal is 'read' by a power amplifier. Should I treat this PCB trace ...
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### Impedance matching and termination resistor

I’m a little confused regarding impedance matching with resistors. As far as I know, the impedance of a trace is a part of its characteristics and it can’t be measured with an ohmmeter. For example, ...
1 vote
40 views

### Is a CAN bus device necessary at the end of the terminated network line?

I am designing a CAN bus network with three devices near one end and one device at the other end about 8' away. As long as I retain the terminator at the far end, is a device at the far end required ...
1 vote
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### Can I drive LVCMOS12 on Xilinx Artix-7 at 100 Mbps?

I'm currently planning a setup as shown below, where I need to operate the GPIO on my chip at a data rate of 100 Mbps. My biggest concern is whether it is a feasible to drive LVCMOS12 on Xilinx Artix-...
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1 vote
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### Will termination resistors help with USB data line "dead legs"?

I'm designing a USB switch, using small relays to connect a USB peripheral to any one of ten PCs. The USB traces from the peripheral branch out to ten different relays. I anticipate these "dead ...
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### Why would a low-pass filter be connected to +5V on an RS422 differential line?

I am interested in a datasheet's schematic for my own PCB design of a similar system. In my system, I am receiving an RS-422 differential line, and would simply be tempted to put a 100 Ohm terminating ...
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### HDMI termination board

We are trying to make one HDMI termination board. This board will plug-in into my motherboard and emulate 1080p display. I want to use this termination board for EMC chamber testing of the motherboard ...
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### Termination capacitor value & grounding

I have read discussion on an article on the value of bob smith termination resistor, which is 75 Ω. Basically, the idea of bob-smith termination is to provide a sink for common-mode noise that may ...
522 views

### MAX3362 RS485 IC connection with ESP32

I am using MAX3362 RS485 serial data transfer IC with ESP32. Marked pins 1, 2 and 3 are connected to GPIOs of ESP32. Do I need to add any additional pull-up resistors or some termination resistors or ...
43 views

### Is specific resistor and capacitor material type required for termination of high speed lines on PCB?

Most resistors will be metal film (aka thin film) and most capacitors will be ceramic (class II dielectric). Small components have less parasitive inductance than larger ones. There are different type ...
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### Should I put a termination resistor?

I am a beginner in electronics and am trying to design a PCB where a buffer (BUF634A) output will be connected to an AD8138 (Differential ADC driver). In the PCB's previous iteration, I used a ...
1 vote
128 views

### Expected Outcome of a LVDS Transmitter Output if there's no Termination Resistor

I know this sounds like a silly question, but what would the expected waveform of a LVDS transmitter that has no termination resistor look like? If the expected output were to be a 20 MHz LVDS clock ...
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### Drive strength and termination on a 50MHz multi-card backplane bus

I'm helping someone design a spec for a computing ecosystem based on Z80 and Eurocard. One of the challenges is that we want to support modern Z80 chips clocked at up to 50MHz, which means we have to ...
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### HCSL source vs. end termination

Regarding HCSL I wonder why there is source termination at all? If in case of source termination, at receiver side there is no termination or a high impedance input, then the input reflects nearly all ...
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### General guidelines to avoid damaging RF components

So, I am a young researcher in physics and use RF components like splitters, mixers, couplers, amplifiers, etc. These are not high voltage amplitudes at all - at most a few volts - often hundreds of ...
420 views

### Thevenin termination and RC termination for transmission line

Using series or parallel termination resistor aims to improve signal integrity by reducing reflections caused by discontinuities in the characteristic impedance. This much is clear. What is not clear ...
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1 vote
584 views

### Why does voltage in RS485 bus change significantly when termination resistor is connected?

I've set up the following simple, non-terminated RS-485 network: The bus is 10m long CAT5e cable, carrying a 4800 baud signal. RS-485 transceiver (TRX) is an XY-k485 module (MAX485-based). ...
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### TTL bus termination physical circuit layout

I'm breadboarding a simple data bus terminator for a 1970s TTL computer bus that was normally unterminated. I'm trying both passive and active termination to see how they work, but have a question on ...
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### Is this a right magnetics termination for PoE and non-PoE application

I came across the below schematic image while trying to read Bob-smith termination. Would there be any problems with the termination on the right side with and without PoE? Can someone explain a ...
305 views

### Understanding passive TTL termination

I've been working with 1970s devices and an unterminated system bus. I am adding termination to that but want to first understand a circuit that I have seen to make sure I understand what's going on. ...
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1 vote
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### Terminated RC filter

Few days ago I asked in another thread if there was an easier way to get an expression for a transfer function of the circuit shown below in a form H(w)=H(0)*N(w)/D(w). I wanted an analytical ...
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181 views

### Buffer for driving VMEbus

I am working on a project where I am reusing a VMEbus backplane to create a bus between some cards of my own design. This backplane has passive termination on both ends. I am trying to find a buffer ...
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1 vote
533 views

### Conducted Emissions for Ethernet ports

A device has a DC power port as well as 2 Ethernet ports. One of the ethernet ports supports PoE++. Basically, the EUT can be powered through PoE. I have a question regarding Conducted Emissions ...
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### CAN FD termination with plugged in modules

Is it possible to use CAN FD in scenario in which there is single main device and additional modules are plugged or hot plugged into each another? MAIN->MOD1->MOD2->MODn The main device will ...
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1 vote
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### How to determine the rise time to treat if the signal as a transmission line?

I know that If the length of the track is between 1/6 or 1/4 of the effective length of a feature like an edge a system can be regarded as lumped. BUT A a lot of times, the rise time cannot be taken ...
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1 vote
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### Impedance matching 133 MHz - Topology and terminating resistor concerns

I am using the QSPI bus of the RP2040 to talk to a flash chip. I am also putting 8 more chips (PSRAMs) on that bus in my design, and a second RP2040 to load them. The datasheet for the RP2040 isn't ...
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### Why is the DDR termination voltage half the supply voltage? [closed]

Why is the DDR termination voltage (VTT) one-half the VDD voltage?
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### Is there an antenna problem with CAN Bus selectable split termination header pin?

I am trying to implement a jumper-selectable CAN Bus termination with a SPLIT configuration, as shown in this Analog Devices example: https://www.analog.com/media/en/technical-documentation/user-...
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### RS-485 bias & termination resistors with 3.3v transceiver and 100 ohm cable

I am trying to connect two boards together with a few feet of Cat 5e cable. Both boards will be using 3.3v RS-485 transceivers (ISL83483 or similar). Using this calculator, I entered 3.3v for supply ...
238 views

### How to know whether a differential transceiver is internally terminated for common mode voltage or not?

In a keynote by Rick Hartly titled "What your Differential Pairs Wish You Knew", it is suggested that especially at high speeds, it is necessary to terminate the differential pair not with ...
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### SPI bus termination for variable line length / variable number of slaves

There is a lot of information online for SPI bus termination, but my situation is a little bit different. I have created a system with the intention of 'plug and play' IMUs. Although the main ...
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### Does SPE (Single Pair Ethernet) require termination?

It is stated that it needs 100 ohm termination resistor but is it end of the each line externally?
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### Three-state buffer SPI termination requirements

I have question regarding SPI termination when using three-state buffers: Do we need termination resistor from master to three-state buffers (since ICs are very close) If we do, then do calculate the ...
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### CAN Bus termination resistor in only 2 device connection

A termination resistor in CAN ( .. or other differential pair communication like RS485 ) is necessary to absorb reflection. The value is related to wire length, electrical frequency, baud rate. It ...
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### Novel CAN bus design - needs criticism

I'm designing a CAN bus interface for a PCB I'm working on. CAN and high speed/long distances are new to me, so I have a list of concerns about my design ideas, and I would appreciate someone with ...
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### RJ45 termination in fast ethernet

I am working with fast Ethernet. My question is that we are using only two pairs in 100 Mbps. How will I terminate pin 4 and 5 and pin 7 and 8? Can I separately terminate magnetic center tap with a 75 ...
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### SerDes LVDS termination with isolation

I have the following chain: There are two FPGAs (Microsemi and Lattice) that I am connecting through LVDS SerDes communication. The two FPGAs have isolated power thus the isolation for the data in ...
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### Capacitors on center tap

This is a follow up to a previous question that I asked here Why do we add capacitors on center taps to the magnetics when connecting to an Ethernet PHY? Also what is the reason on why we terminate ...
982 views

### Tap into CAN bus

I'm thinking about tapping into an existing CAN bus. I'm going to attach in a middle point, and I don't want to introduce any issue in the original bus. In order not to disturb the original bus with ...
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### Bob Smith Termination - Where should we use it? [duplicate]

What is a Bob-smith termination and why do we use it? I've seen it being using in Ethernet RJ-45 connectors where it is terminated to Chassis ground? Can someone tell me how this type of termination ...