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Questions tagged [decoupling]

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4
votes
4answers
190 views

Preventing spikes when plugging jacks

I'm using an 8 output DAC (LTC2666) to control synthesizers via mono 3.5mm jack connections. It works fine most of the time but every once in a while, plugging in a jack into the synthesizer will ...
0
votes
1answer
28 views

During DC restoration of a video signal how is the first sync pulse detected?

DC restoration of an AC coupled video signal can be performed by clamping to some reference voltage, during the horizontal sync periods of the video. This all seems fine in a running system, when the ...
0
votes
0answers
36 views

STM8L101F1 VDD and VSS decoupling misunderstanding

I am working on small PCB design using STM8L101F1. Its power supply pair VDD-VSS needs to be ...
0
votes
1answer
109 views

Bulk capacitor placement/routing

Are there common guidelines for bulk capacitors? If I have the decoupling capacitor placement shown below (where the vias connect to Vcc and GND planes): And I need to place a bulk capacitor in ...
116
votes
5answers
18k views

Why does Samsung include useless capacitors? [closed]

I do component-level repair of tablet mainboards, and I have seen this puzzling situation on two different models of Samsung tablet mainboards so far (SM-T210, SM-T818A). There are ceramic chip ...
-2
votes
3answers
163 views

Can a decoupling capacitor protect against non sinusoidal spikes?

If we have a decoupling capacitor on a 5v input, and suddenly the input goes up from 5v to 10v and back to 5v, the voltage across the capacitor will rise to 10v and then discharge through R2 down to ...
0
votes
3answers
92 views

LM2664 noise in the OPAMPS output signal. How to remove

I have 4 opamps powered from the LM2664. Two of them (1MHZ 1.6V R-R) are preparing the offset voltage for the pair of the OPA4141 which actually provide the signal for the ADC It works as expected ...
0
votes
1answer
109 views

Help to choose caps for noise filtering

I am trying to build a project with ESP8266. To save PCB space and avoid complexity I have chosen to use Hi-Link's SMPS module for 220V AC- 5V DC conversion. I am bad when it comes to noise / ...
0
votes
1answer
48 views

Frequency range of interest in PCB decoupling network

All the material I found about decoupling write "[...] low impedance in the frequency range of interest [...]" but it's never discussed how this is defined. Does it come from The external noise on ...
1
vote
1answer
209 views

DDR4 pull-up resistors and decoupling clock lines

I am trying to understand the layout of a DDR4 chip connected to a FPGA. The schematic follows: I tried to look for datasheets from the memory manufacturer explaining how to properly pull-up or pull-...
0
votes
1answer
88 views

Converting 5v to 3.3V for GPS purpose while keeping noise at the lowest

I'm trying to create a very simple module that consist in powering a GPS ublox - NEO-M8U - with a micro USB & using an active antenna. Later on, I will add more features but I just want to make ...
0
votes
4answers
251 views

How to add decoupling capacitors to already mounted ICs

I have this board with three DIP ICs already mounted in their sockets. The decoupling schematic is this: So we have a sum of 8 ceramic caps and 2 electrolytic ones. So how do i solder them? Should i ...
0
votes
1answer
376 views

Choosing a bypass capacitor for long wire

I've built an IR remote and for integration purpose, I need to bring the led about 1m (3 feet) from the microcontroler. Led Freq is 455KHz. Temperature considered as room temperature. I choose to ...
1
vote
2answers
610 views

Proper Decoupling

I have this circuit connected to an Arduino DUE. It is an audio application and it works, but I have a ton of noise in my project. I initially thought it was quantization noise because the ADCs are ...
0
votes
2answers
73 views

How to decouple a negative feedback loop in DC?

My question is open ended, but I provided an example to explain the question better. R19 and R8 in the middle of the pic form a negative feedback loop. They set the gain of the amplifier. I need to ...
2
votes
1answer
240 views

IC Decoupling caps placement/routing [duplicate]

I've been looking around the web about placement and proper net routing of decoupling capacitors for ICs. In this example I have a pic micro-controller using internal clock at 80MHZ, with the ...
0
votes
1answer
64 views

48V coupling into digital signal

I have a large thruster that requires 48V to operate, which I've provided through an isolated supply (Vicor DC/DC isolated converters). The thruster uses a Hall-effect sensor to adjust the speed (-5V ...
0
votes
3answers
89 views

Should the PLL pins be decoupled on an MCU?

Literature covers very well the decoupling of many pin types on a microcontroller, such as from muRata and E2V. The currents in are decoupled from the ground plane. PLL's are also grounded, however I ...
11
votes
3answers
1k views

More Vdd than Vss Pins

I am currently working on my first microcontroller hardware design; I had a microcontroller class in college, but it focused on the software side of things, and used a pre-made development board (for ...
0
votes
1answer
290 views

Why 0.1u decoupling capacitors?

Why is always prefered the value of 0.1u as decoupling capacitors that they placed very close to the chips? Why don't use larger, like 0.22u, 0.47u, 0.68u or 1u for example?
0
votes
2answers
136 views

VCC filtering for sensor

I'm designing an application for this mangetic angular sensor https://www.monolithicpower.com/Portals/0/Documents/Position%20Sensors/datasheet_MA700_rev1.2.pdf Because this is precise and sensitive ...
1
vote
1answer
174 views

multiple decoupling capacitor circuits (integrating multiple circuits)

I'm integrating two circuits into one. One being an Arduino Pro Mini (ATMega328P) and the other being a CAN controller+transceiver. For the Aduino Pro Mini, I'm using a TLF80511TF50 (5V LDO). I've ...
1
vote
1answer
96 views

Integrating two I2C sensors into a single circuit

I have two I2C sensors that I want to combine into a single circuit. Here are the schematics for each sensor side-by-side (i.e. not combined into single circuit). The BME280 datasheet states the ...
0
votes
3answers
191 views

Vcc decoupling, how to do exactly?

I understand what decoupling is needed, but I did not understand how it is applied. For example, in this scheme that I found, there are many capacitors at the output. (Is a DC-DC converter). Some ...
8
votes
2answers
813 views

Need help reverse engineering and understanding a small circuit

I am an electronic student, and one day I opened an energy meter I have at home called EM21, and found out that its body is comprised of two major components: The meter body, that connects to the ...
2
votes
1answer
246 views

Decoupling Capacitors on each VDD pin on a tiny 36/49 ball WLCSP/µBGA chip really necessary?

I've searched this and many other sources on Info on decoupling capacitor placement, but couldn't find any info specific enough to my current problem. I'm currently doing a PCB Layout for a tiny, ...
1
vote
5answers
2k views

Is there a formula to determine the size of decoupling capacitors? [duplicate]

I have used many decoupling capacitors in circuits and have seen them in many textbooks, but they never give an explanation about why they picked a certain size of capacitor. Everyone seems to have a ...
1
vote
2answers
213 views

Decoupling high current load and 5V regulator

I have a 12V DC input from a power adaptor. A LM7805 5V regulator takes this as an input and powers an MCU and some other digital circuitry that will eventually drive a relay through a high-side load ...
3
votes
2answers
503 views

How to isolate a PCB circuit from a high noise source in the nearby

I am designing a circuit that will sense an electric fence shock generator. In my first prototype, it worked very well, except in the time the shock generator creates a spark, when it produces a lot ...
1
vote
3answers
662 views

capacitor placement [closed]

I would like to know is there any standard on placing capacitor on a pcb board. For example, in front of a power supply 3.3V, I put 100p, 10n, 10u, and 1n. How should I put it in the correct order ...
1
vote
2answers
110 views

Integrating multiple sensors onto one board, how many decoupling capacitors do I need?

I am designing a board that will have three MAG3110 sensors on it. In the data sheet, the "Application Circuit" shows 5 capacitors. My question is, if I have three of these sensors on one board, all ...
0
votes
2answers
298 views

Decoupling capacitors for Multiplexer?

I am using a Board with a Cortex M0 to sample signals from force sensors. The sensors have a resistance that corresponds to the force applied, so I am using voltage dividers and read the voltage with ...
0
votes
1answer
515 views

Wrong result in spice simulation of DC Offset at AC coupled diode

I'm playing around with a diode as AM demodulator and have stumbled upon a phenomenon that seems logical but I can't reproduce it in LTSpice. My setup is the following: simulate this circuit – ...
1
vote
2answers
302 views

Low-frequency / DC circuits — noise + decoupling issues

I'm using an AD8421 instrumentation op-amp, and I need to adjust the DC level of the output. As per the datasheet, the VREF input pin needs to be driven by something that asserts a voltage (low output ...
1
vote
5answers
1k views

RC low-pass filters for op-amp power-in pins?

It has been a long-lived tradition of mine to put an RC low-pass between the power supply and each power-in pin of each op-amp, where R is typically 1 to 10 ohms, and C is either 0.1uF ceramic, or ...
1
vote
4answers
900 views

maximum distance between IC power pins and decoupling capacitor

Since I introduced decoupling caps to my design, my auto-routing progress has dropped. Currently my PCB track width is set between 0.24mm and 0.26mm (I'm trying to aim for 0.26mm depending on how ...
2
votes
1answer
116 views

Good practice splitting of power and ground nets

In a design I'm working on I've got a few discrete sections with dedicated purposes, mostly independent of each other but with a few basic interconnects (e.g. SPI / UART). In order to make testing ...
3
votes
2answers
246 views

Remove high-speed noise from power supply

Could anyone help me a bit sort this out? I have implemented the following schematic on a PCB for the decoupling of a supply rail of an Ethernet Switch. More specifically it is the IO supply of the ...
18
votes
6answers
4k views

Can a decoupling capacitor be too large?

For my project containing an ATtiny85 running at 32.768 kHz using an external watch crystal I thought I'd include a 1 uF decoupling capacitor near the MCU power pin for good measure. However, reading ...
0
votes
3answers
159 views

Earth decoupled power supply

I have an electrocardiogram sensing circuit that uses an INA321 amplifier for common mode rejection on two measurement electrodes. The device is meant for hand-to-hand measurement of the heart rate ...
3
votes
2answers
582 views

Can a single, large multilayer ceramic capacitor replace the classic electrolytic + ceramic decoupling capacitor arrangement?

In classic decoupling designs, it is common to see a large (10 µF or bigger) electrolytic capacitor in parallel with a smaller ceramic capacitor (in the range of 0.1 µF). The larger electrolytic ...
2
votes
1answer
323 views

Decoupling capacitors design [duplicate]

When designing decoupling capacitors why there are always parallel capacitors arrangements with decreasing values? It seems a redundancy to have this kind of configuration because the equivalent ...
1
vote
0answers
151 views

Decoupling caps near ICs, but how much near? [duplicate]

I always read about decoupling CAPs should be near to MCU pins, but how much near? If we are talking about very small caps of 0201 dimensions, wich distance is good from MCU power pin? Look at this ...
0
votes
2answers
74 views

Decoupling capacitors for TLC5917

For a project involving driving a bunch of LEDs we are using TLC5917 driver IC's (datasheet). I read up upon decoupling and smoothing capacitors, but I am uncertain if and how we should use them. We ...
0
votes
1answer
146 views

Multiple TLC5940s on PCB “dropping out” when many outputs turned on

I've designed a PCB to connect 12 TLC5940s to an 8x8x8 RGB LED cube through 3 64-pin headers, which I will include screenshots of below. I have a separate board for controlling the anodes for ...
2
votes
1answer
179 views

Choosing decoupling caps

I know there are other questions on this site about decoupling, but I do not feel they accurately cover the full decision process. I am interested in knowing the decisions that go into choosing ...
5
votes
1answer
380 views

Encoder PCB design - grounding, noise and decoupling

Hi first time posting here. There always seems to be helpful answers and tips. Okay my question is simply are there any glaring mistakes in my approach to the PCB layout (see image links below), I'm ...
2
votes
1answer
97 views

How to isolate a zero-cross detector from phase-controlled simistor?

To control the average voltage, output by a triac, the controller needs to know the time of the zero crossing. But the circuit for detecting the zero-crossing is a sensor, vulnerable to noise; taking ...
7
votes
4answers
12k views

AC-coupling capacitors for high-speed differential interfaces

Can you explain me why and where I should put AC-coupling capacitors (usually around 0.1uF) on high-speed (1...5 GHz) differential serial interfaces (like SerDes for Gigabit Ethernet SFP modules)? ...
9
votes
2answers
2k views

Connecting a decoupling capacitor straight to the ground plane

I had always thought that if an IC is grounded to the ground plane then connecting a decoupling capacitor to VDD on one side and straight to ground plane on other side as shown below is acceptable: ...