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Questions tagged [decoupling-capacitor]

A capacitor, usually ceramic, used to provide instantaneous energy to a local circuit.

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Decoupling Capacitor Usage Conditions

I understand that decoupling capacitors are small capacitors (often 100nF) used on VCC/VDD on ICs. When are they most required and when is it just silly using them on every IC. Are they better used ...
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83 views

Implementation of Decoupling capacitor [closed]

I have schematic for decoupling capacitors (3 set of 0.1uF,1nF,10pF): And I've implemented that in this way: And there is ADI reference for easy evaluation: And the ground pins of decoupling caps ...
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854 views

How do I know where to put stitching vias?

I'm working on a PCB that allows me to attach a TSSOP IO expander to a breadboard more easily for experimenting. I asked a question regarding the configuration of decoupling capacitors for an IC with ...
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127 views

Is this a valid configuration for decoupling capacitors on an IC with two supply pins?

I have a project that's using an IC that only comes in SMD packages. With my limited soldering experience, I think I could potentially solder a TSSOP, but I think QFN is well beyond my capabilities. ...
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51 views

Boost Converter (TPS61322): Loop Stability with Large Capacitors

I am using a TPS61322 boost converter to convert a minimum of 1.3V (single-cell alkaline) to 3.3V (using the TPS613221A version). This device needs two passives: an input inductor and an output ...
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62 views

Decoupling cap value?

We are a design using 3 decoupling capacitors the value are 47 uF 16 V X5R, but we are having trouble with the supplier. I have an idea to replace them with 1 capacitor 100 uF, 1 10 uF and 0.1 uF. ...
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60 views

Bypass caps under BGA: Should I isolate vias from planes?

I'm placing bypass capacitors underneath a BGA package. In some cases the caps cannot land directly on the vias-in-pad ("VIP"), so I'll need short traces from the VIPs to the caps: In this example ...
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67 views

Do I need decoupling capacitors when I'm PWMing an LED?

I'm a hobbyist (well, less than a hobbyist really) trying to layout my first PCB design. I'm somewhat familiar with the concept of decoupling capacitors. I'm fading 3 LEDs in and out (really, it's ...
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51 views

Decoupling cap placement

I'm currently making a PCB with 2 ethernet ports and a CPU running at 200+ Mhz. This isn't the fastest PCB by any means and I don't foresee any issues with the placements, however in the future I ...
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99 views

Decoupling capacitors introduce more noise on transmitter power amplifier

I have an issue that I can't understand and looking for your help to give me some insight to solve it. I'm using a module named dw1000 that is used to measure distance using UWB at 6.4Ghz, 3.95 Ghz......
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119 views

What are some of the reasons for voltage spikes in voltage regulated DC circuits?

Decoupling capacitors are often used to protect ICs against voltage spikes even in circuits that contain voltage regulation of some sort (even something as simple as a zener shunt) What causes ...
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62 views

H-Bridge Adjustable Slew Rate: Why is a decoupling capacitor needed?

I am designing a simple 3-phase inverter for BLDC Motor control. For that purpose, i plan to use a IFX007T from Infineon. The slew rate is controlled via a resistance connected in series to SR pin. ...
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50 views

What is the purpose of these capacitors in this State Variable Filter schematic?

I need some help understanding this schematic. It's a state variable filter based parametric equalizer. What are the capacitors C4, C5 and C6 for? Are those coupling capacitors like C1 and C7? Are ...
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88 views

Attaching a decoupling capacitor to PCB. What should go where?

I'm nearly finished with the recreation of a PCB that'll be used in creating a modchip for my PlayStation 1 that is gathering dust. I'm basing it off a modchip I bought last year but accidentally ...
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1answer
30 views

Pololu A4988 Decoupling Capacitors

My son (9yrs) has become interested in robotics. I did a course on it in college, but that was a LOOONG time ago and the course was much more rooted in programming than it was in electrical ...
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STM8L101F1 VDD and VSS decoupling misunderstanding

I am working on small PCB design using STM8L101F1. Its power supply pair VDD-VSS needs to be ...
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256 views

Do chips really need multiple values of decoupling capacitor in the same packages?

A similar question is asked here: "two bypass/decoupling capacitors" rule? But that question was about parallel bypass capacitors without mentioning package size (but the answers mostly ...
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126 views

How to prevent tombstoning using via-in-pad with small SMD discretes

My current project is using via-in-pad technology for BGA chips. They are proper VIPs: filled with conductive material and planed flat. I would also like to use these VIPs for my discrete decoupling ...
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1answer
65 views

Using capacitor to protect circuit from split second power disconnects

I have a circuit powered by a 9V battery. The circuit will be subjected to significant vibrations. I want the circuit to not power off if the battery is disconnected for a second. Would a capacitor in ...
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1answer
118 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 ...
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3answers
140 views

How to calculate the input and output capacitors of a common emitter amplifier using BJT?

Sorry if the question is stupid, but my head is still hard as a coconut and I am learning... I am dealing with this circuit that I have calculated from scratch. This circuit was designed to have ...
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1answer
69 views

repairing damage: what size ceramic bypass capacitor

Repairing a motor control board from a washing machine. A 1206 ceramic cap was burned up, there's a bulk electrolytic in parallel, rated 200v 1000uF. I've attached the example schematic for the ic (...
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72 views

LM350 voltage rises with capacitor

I'm really trying to understand my voltage regulator (LM350T), but I think I'm still missing a few things. If I add cap C3 (I've tried 0.1uF and 10uF) to the output in the circuit below (note that the ...
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1answer
39 views

Spartan II XC2S50 TQG144 ASM 13 - decoupling capacitor values

I have a damaged board out of a CCD camera that requires replacement of the Spartan II FPGA chip (XC2S50 TQG144 ASM 13) and a few decoupling ceramic caps around its periphery. There is no schematic or ...
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5answers
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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 ...
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1answer
142 views

Wire to VDD or GND?

In the circuit below, there are four LTC485 ICs, one input (left), three for output (right). Pins 2, 3 and 8 are going to +5V, as well as GND. So where should I connect them to? Should I wire them all ...
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494 views

Which type of capacitor to use for matching the data sheet?

I want to choose decoupling capacitors for some microcontroller peripherals, which in their data sheets only specify some capacitans. Since you have quite a choice of passive components and the data ...
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91 views

Longest, thinnest trace length to decoupling capacitor before capacitor is effectively useless

I was told time and time again to always put decoupling capacitors as close to the IC pin's VCC as possible. Sometimes when I make complex boards, I try my best to put the capacitor lead so close to ...
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2answers
101 views

Inductor on VDD pin

I have found that schematic. On the VDD pin of the processor, there is an inductor (L1). Could someone let me know what is the role of the inductor there? Usually, reference diagrams on such kind of ...
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1answer
124 views

Via inside decoupling capacitor pad?

If I place my decoupling capacitor (more or less) like shown in the figure: I wonder: can the vias be inside the pads? (one via inside each). Two advantages I can see are: (1) we avoid the ...
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3answers
168 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 ...
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466 views

STM32 MCU PCB layout review (crystal & decoupling & ADC)

Introduction: I am designing a hobby electronic for first time, using STM32 to control a soldering tip. I read many documents of PCB layout, and also many information from this forum. And this is my ...
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207 views

Could a larger capacitor, at the output of the SMPS, destroy components with larger current draw when its being charged?

I am designing a SEPIC converter using a LT8364 for "power aplications" and a buck converter using a TPS62125 for powering a MCU. Since I have a bunch (>100pcs) of 100uF, 16V, electrolitic caps ...
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49 views

3.6V battery filtering Capacitor calculation

I am using the follow battery as power supply: http://uk.farnell.com/eve/er26500/battery-lithium-3-6v-c/dp/1973582 The circuit demands a constant current of 0.01 mA until an interrupt happens where ...
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120 views

Why Can't I Turned On The Relay If the Supply Come From The LDO Regulator

I'm trying to turned on a 5V SPDT Electromechanical Relay. It is planned to be used with microcontroller application. Below is the circuit that I wired on a protoboard: When connected like that and ...
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79 views

Most advantageous decoupling for multiple voltages

I'm trying to figure out if I can improve the elimination of noise. I always decouple my IC's by connecting VCC and ground together with a 100nF ceramic capacitor, But I'm curious. In each picture ...
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1answer
124 views

Mark decoupling capacitor

I'm working on a PCB. As ECAD software I am using KiCAD. All ICs will get two decoupling capacitor. One 100n ceramic and a 10uF electrolytic. For now I place them like shown in the picture at each ...
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1answer
66 views

High Frequency Excitation on Class D Amplifier

I'm building a discretized class D audio amplifier that's running at 250kHz that's designed to run on a single ended 80V supply. I was seeing very high amplitude, high frequency excitations on the ...
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112 views

How to find coupling and decoupling capacitor values?

I am trying to learn receiver design, one thing I noticed is the use of coupling capacitors and decoupling capacitors and incuctors. There were set of standard values such as 100 pF, 1000 pF or 0.1 uF ...
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43 views

How does same capacitor with different dielectric affects the circuit?

I am working on a project and finalizing 0.1uF capacitor with 50VDC(decoupling). I am finding with different dielectrics. My question is how does two diffrenet capacitor having same capacitance and ...
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2answers
160 views

Why is a tantalum capacitor recommended?

I am looking at the datasheet of an accelerometer (ADXL345), and in the power supply decoupling section, it says to use a tantalum capacitor. Why is this recommended?
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96 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 ...
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583 views

how can i calculate decoupling capacitor value?

How can i calculate decoupling capacitor value? Which amount of noise we can filter use it.why use here 10uf , 0.1uf capacitor?
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649 views

how to place decoupling capacitors on a four-layer board for through-hole components?

From what I've read online, for SMT components there should be traces from VCC/GND pins to the capacitor and then vias to the ground and power planes. The situation is a bit different for through-...
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1answer
133 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 / ...
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302 views

How to prevent a microcontroller to reboot due to Vcc fluctuations?

Case #1: I have a pump station with an autonomous 240V pump motor switched by a 240V pressure switch, feeding a pressure tank to a max. pressure. After said tank are four 24V solenoid valves (250mA ...
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1answer
122 views

Why should small capacitors be placed far away from the 'output' pin on a medium-sized LDO?

Reading the datasheet for an AZ1117E adjustable LDO voltage regulator capable of supplying 1A, I noticed the following recommendation, which I don't understand: "Close to the OUTPUT pin, it is not ...
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130 views

Can you simply remove a shorting decoupling capacitor without replacing it? [closed]

In a digital system, not RF related. If there are numerous filter caps on the same power rail but only one fails shorted, can you just remove without replacing since the others will remain in circuit? ...
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1answer
50 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 ...
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2answers
110 views

Bypass Capacitors - Why do they not provide voltage spikes back down the line?

I am new to electrical engineering. Please excuse me if I use the wrong terms. (Welcome to correct me tho ;-) ) I am learning about capacitors, and I have been studying a circuit diagram explaining ...