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Questions tagged [signal-integrity]

Questions regarding how to properly ensure Signal Integrity, protection from noise, shielding, proper pcb layout.

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2answers
567 views

What makes “quality” analog AV cables better than cheap cables? [closed]

I want to upgrade my retro game setup from a mix of composite and RF to a mix of S-video and component, with some composite for the really old stuff that doesn't support S-video. How can I distinguish ...
0
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0answers
59 views

Power line between data lines

I am finalizing my design which connects a USB Controller (FT601) with the FPGA (MachXO2). There is last thing I am not particularly happy about and I would like your feedback on that. In the ...
0
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1answer
50 views

VCC on surface or inner layer on 4-layer board?

If I can get away with, I will use 6-layer design where I get two dedicated GND planes, L2 and L5, which creates strong reference plane for traces on L1, L3 and L6. When you're working with 4 layers,...
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1answer
67 views

Could shielding (not grounded) affect signal integrity?

I'm trying to shield 6 flat cables that give me some communication issues because I thought that there might be cross-talk or other sources of interference that cause the problem. The shielding is ...
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3answers
118 views

How do you know if impedance is the same for 2 ICs?

in my last question I got some very interesting answers that made rethink a lot about my design as to whether or not I need termination resistors at all. Additionally, the design proposed in this ...
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3answers
95 views

Large number of termination resistors and bi-directional signals

I am designing PCB which has an FT601 for USB communication. No matter how hard I tried, I could not keep the traces short enough in order to avoid reflections and simulation was revealing significant ...
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2answers
52 views

How protect analog input connected to thermistor through long wires

I'm developing a data acquisition board for 8 thermistors hooked up through 3 feet wires. The board is gonna be installed inside a package unit air conditioning. In there, we have compressors, fan ...
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2answers
68 views

Reducing noise that grows with frequency

I have a project in university where my professor gave us the following problem: There is a transducer generating an AC signal with amplitude of 7.5mV and a frequency range from 50Hz to 150Hz. This ...
0
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1answer
45 views

Is there a problem connecting PSU grounds to earth for an isolated signal chain in this scenario?

For a precision and simultaneous analog signal data acquisition; several force, temperature and acceleration transducer outputs are coupled to a daq board input channels through signal conditioning ...
1
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1answer
44 views

3 wire signal to 4 core shielded twisted pair

So I have some flow sensors, which have a 3 wire interface. The three wires are 5V, signal, and ground. Signal is pulse output that varies between 5V and ground at a maximum frequency of about 200 Hz....
0
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1answer
64 views

Altium - design rule check does not match with signal integrity for impedance

I have designed a 2-layer PCB with Altium Designer. I placed an impedance rule of 50 Ohm in trace width rule section. When I run the design rule check, there is no impedance error. However, when I ...
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1answer
40 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 ...
2
votes
2answers
187 views

How to achieve 100ohm impedance for HDMI differential pair on FR4?

I have a 6 layer FR4 PCB, and want to achieve 100ohm impedance on HDMI differential pairs. I am only using top and bottom layer for differential pairs, and following are my parameters: Trace width= 3....
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0answers
25 views

Signal Attenuation TVS and series resistor

This question is in regards to signal attenuation on high speed data lines like RS-485 (and any others as well). I'm new to the signal world, so please bear with me here. Are there some useful ...
0
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1answer
37 views

Boosting the Analogue Response of a Sensor

I have a A1308KUATN-9-T Hall Effect sensor with the following sensitivity (from the data sheet): As you can see, the sensitivity comes to about 9mV per Gauss on average. My calculations (see below ...
3
votes
1answer
125 views

Analogue (or digital) signal integrity with multiple sources of noise

tldr: Can I transmit an analog signal through a noisy environment without it being corrupted, or should I use a digital signal instead? My requirement is to transmit a signal from a MA3 absolute ...
0
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1answer
40 views

Digital signal integrity & grounding

I have a battery operated device with an old B&W LCD in it. I'm tapping to the display bus and would like to input it into an FPGA for some processing. The bus includes vertical and horizontal ...
0
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3answers
69 views

Tektronix function generator THD

I am confused by the datasheet of the AFG3021C: https://www.tek.com/link-click-count?nid=75006&url=https%3A//download.tek.com/datasheet/AFG3000C-Arbitrary-Function-Generator-Datasheet-75W282817....
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0answers
42 views

Does the location matter when performing unbalanced to balanced source conversion for this scenario?

Below circuit shows the issue when the output impedance of a DC-like source V is not balanced when coupled to a Diff Input(differential input of a data-acquisition board). As you see as an example for ...
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0answers
70 views

How do passive boosters/repeaters (such as a HDMI 'booster') work?

I have a HDMI device and I want to connect it to something very far away. I notice you can buy a HDMI booster to do this, but some of them are unpowered (they take no external power). How can a signal ...
8
votes
3answers
846 views

If temperature is not an issue, what can be said about the different ceramic dielectrics

Let’s assume we have a circuit whose operating ambient temperature range is well-regulated to 25+-5C. Besides cost, what would be the use cases for the different ceramic dielectric types? In other ...
4
votes
1answer
123 views

JTAG trace length affecting programming ability

I've recently had a design made that requires a programming port to be located quite far from the device I'm trying to program. This has meant that my cJTAG traces are around 13cm long. I think as a ...
1
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1answer
86 views

I2C bus line over different layers in an arc

I have the following board design in mind: It's a 4 layer, ~5cm diameter board where 10 slave PCB's will be soldered to it that are connected over the I2C bus. The trace line you see is roughly 8 cm ...
0
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1answer
48 views

Are digital inputs of data acquisition devices differential or single ended?

I read that in almost all daq board datasheets the analog inputs are specified as single ended or differential inputs. But the same daq have digital I/O ports. How can one understand whether the ...
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0answers
82 views

Reducing electromagnetic interference in underwater acoustics cables

Our college underwater robotics team has a passive acoustics system with four hydrophones that provide an analog signal typically between +/- 200 mV corresponding to the sound wave at that point in ...
2
votes
1answer
233 views

Grounding and Signal Integrity of my PCB Layout (ADC, SMPS, SD card, USB)

I am currently designing a battery monitoring system for an 8 cell lithium battery pack. I originally made the device using a STM32 dev board and breadboard, with an SD card to log data. The system ...
1
vote
2answers
199 views

Advice for 25-50 Mbit SPI lines - PCB design

I would like to ask some advice for my layout design. I am working on a layout design. The designed PCB will be a Beaglebone Black (BBB) extension card. It is a four layer PCB with the following ...
0
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0answers
31 views

Coupling differential line to a single ended daq

Sorry for the primitive drawing but it was for clarity of the question: If a differential balanced signal will be conveyed to a single ended inputs of a DAQ, what would be the proper connection? ...
1
vote
1answer
140 views

Locating pairs on an LVDS cable

For a 2-row connector intended to interface a cable to a PCB, which method is preferable for twisted pair LVDS signals? Horizontal Pairs: LVDS1-    LVDS1+    ...
1
vote
1answer
148 views

PH Probe Unstable Measurement

I've recently set up a small circuit for PH measurement using a BNC PH electrode. A picture of my circuit can be seen below: The linear reference REF1 alongside opamp U1A serve to generate a 2.5V ...
2
votes
1answer
375 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 ...
0
votes
1answer
91 views

How to use 0.1 inch header footprint for high speed signals?

I have a board which has a dual 0.1 inch header footprint (the totally standard kind you see everywhere). Trouble is, this carries a fast 300-500 Mbit DDR LVDS signal (!!) to another board. Okay, so ...
8
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4answers
2k views

Understanding the Maximum Speed that can be Transmitted over a Cable

I am trying to source a FFC/FPC cable for USB3.0 (+5gbps). This brought me to the question of signal transmission. I'm somewhat of a beginner in this topic. I know that you should match impedance on ...
0
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1answer
153 views

Is this alternator W RPM input circuit ok and how can I improve it?

I need a robust and reliable way of taking a RPM signal from the W terminal of a standard automotive alternator. Most of the time the signal will come from a 12V alternator but there is a requirement ...
0
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1answer
89 views

Difference between conventional Eye-diagram voltage plot and “Eye-density” plot in ADS Keysight Simulation

I know what is eye diagram. It is the sampled voltage plot at the clock frequency (Usually) of my circuit and superimposed. If the logic 0 corresponds ...
0
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4answers
61 views

Single voltage power supply to +/- rails

I have a wall wart coming into my circuit in the DC barrel jack shown in the picture. I want to have a positive and negative rail for my op amps as I am unsure of the effect of biasing my signal lines....
1
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1answer
106 views

Gounding for EMI and signal integrity - LED Matrix multiboard design

I would like to implement a LED Matrix circuit like this one, where the LED matrix enclosed within the blue dots will be on a seperate PCB than the rest of the circuit. Since this will be a ...
1
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1answer
83 views

How to route a nasty signal (200V/µs)?

I have to route this signal for a distance of ~70mm† through a dense (mostly digital) 2-sided board. The signal is generated externally and I have no control over its shape, it's basically a pulse ...
0
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2answers
203 views

What does it mean if eye diagram voltage (0 and 1 level) goes negative?

I have created a differential channel and was testing the channel with simple testbench to check the eye diagram. Now I know the channel performance is very bad (It of several PCB transmission lines, ...
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2answers
128 views

High Speed Signal on Large Circular Ring

It's frequently communicated that when working with signals in the Ghz range, routing is extremely important to signal integrity. Pretty much any inclusion of unnecessary stubs is out of the question, ...
0
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1answer
82 views

Connecting LVDS signal from one PCB to another

I am tryin to connect LVDS signals on one PCB to another. I am using an FFC cable and am trying to understand if signal integrity would become an issue. The shortest FFC cable that I could find is ...
0
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0answers
42 views

Remote triggering by using optoisolators

I need to hardware-trigger three modules from a pulse signal source. According to their data-sheet each module requires between 5 to 15V for trigger high and 0 to 5V for low. Each module draw around ...
0
votes
2answers
61 views

Understanding a common mode signal conditioning module

As far as I understand, normally an ideal differential amplifier(or an instrumentation amp) can reject common mode(CM) voltages up to around its rail voltages. Let's say the rails of the diff. amp ...
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4answers
508 views

Effect of cable capacitance to low frequency analog voltage signal transmission

Regarding sending a low freq. (<150Hz) analog voltage signal with CAT6 STP cable I have heard that: if the frequencies down the cable will be low, there may be an issue with it driving a capacitive ...
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5answers
113 views

Sensor question for low freq

A floating DC voltage output sensor will be powered locally and the signal will be sent outdoors 200 meters far away to a data acquisition board. I didn't receive the sensor yet and don't have the ...
1
vote
1answer
39 views

Output impedance imbalance and CM noise in truly floating sources

In the following Figure 1 and Figure 2, the sensor is the one in dashed box. The output impedance of the sensor is big and in this case is 1k Ohm. And as you see regardless of the sensors are bipolar ...
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1answer
32 views

Comparison of two configurations to balance source impedance

This is a generic question for about frequency sensors. But as an example I use this sensor which has around 1k output impedance. So in below drawing the source in dashed box has 1k output impedance: ...
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3answers
120 views

Should a trace be connected through multiple pins on a pin header?

I'm designing a modular board, where the two modules are connected through pin headers. For mechanical stability I have more pins than traces and my question is that which is the better: route each ...
2
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1answer
138 views

Why doesn't smaller Transmission Lines affect Signal Integrity? [duplicate]

I am reading High Speed Digital Design: A Handbook of Black Magic. It was mentioned that if length of transmission line (Microstrip or stripline) is less than 1/...
0
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2answers
280 views

Multiboard Grounding In High Frequency

How can ground loop be avoided when connecting two system with same ground. This happen in PC whith SATA cable or PCIe Card with seprated power cable. My System Board: I have two pcb each with a ...