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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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5V Switching Regulator Problems

I have a circuit with two supplies. A 19v supply for stepper motors, and a 5v supply for driving the ATMEGA644, 3 stepper motor driver daughter boards, a bluetooth LE daughter board, and 2 ws2812b rgb ...
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34 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 ...
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54 views

Buffer capacitors' role in boost power supply design? [duplicate]

In the power supply design, there are always smaller value capacitors placed at the output.What is the main role played by these capacitors in the module? Check the screenshot attached and I am ...
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350 views

Does a MAX485 need decoupling capacitors?

I am designing a small device with two MAX485 chips. Do they need the decoupling capacitors on the 5V power?
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33 views

PCM5102A in 1.8V mode. Separate 0.1 and 10uF caps for DVDD an LDOO?

I found in the datasheet (33 page, 11.5.1) that when using PCM5102A in 1.8V mode, DVDD and LDOO should be both connected to external 1.8V. What's not clear to me is if I still have to put separate 0.1 ...
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Electrolytic Cap in parallel with ceramic for Decoupling

I wanted to ask if adding a high value electrolytic cap in addition to the ceramic decoupling capacitor in a circuit would make the filtering of high frequency worse. Because electrolytic caps are bad ...
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479 views

Fixed a garage remote by breaking it

I have a garage remote that stopped working. I changed battery and it worked again, but only for a few days. I measured the resistance between the poles of the battery terminals and it was about ...
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152 views

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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94 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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880 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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134 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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73 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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65 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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131 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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75 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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68 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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108 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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124 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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76 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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1answer
60 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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92 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
54 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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49 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 ...
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270 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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1answer
140 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
70 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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166 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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340 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
82 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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100 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
40 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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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 ...
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171 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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495 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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97 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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124 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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158 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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174 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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631 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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4answers
309 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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59 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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2answers
169 views

Relay not turning on when supply comes from LDO Regulator

I'm trying to turn 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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3answers
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
130 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
70 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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144 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
175 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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100 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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787 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?