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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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46 views

Reusing heatsink vias for ground plane connection

This a more elaborate phrasing of my previous question on the subject, which did not get much love. I would appreciate a clear and thorough answer since it is my last question (after a long journey) ...
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1answer
51 views

Ceramic Capacitors vs DC Bias - Derating rule of thumb misleading?

Premise Ceramic capacitors with Class 2 dielectrics (such as X5R and X7R) usually show a reduction of its capacitance value as the applied bias voltage increases. This behavior is more prominent in ...
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2answers
216 views

Reduce impedance for power traces of a decoupling Cap when ground planes are not directly under

I am using an SHTC3 temp and humid sensor to send readings using I2C lines to the MCU. Based on the datasheet for SHTC3 to make sure the sensor is reading ambient temp without the interference of the ...
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3answers
1k views

Decoupling cap routing on a 4 layer PCB

I would like to place some decoupling caps for an IC. The IC is on the top while the caps will be on the bottom, opposite side. How should I route them: A single VIA that connects the IC pin, power ...
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57 views

Why connect a 35 V decoupling capacitor to stepper motor driver when using only a 9 V DC supply?

This circuit uses two hybrid stepper motors each connected to a stepper motor driver A4988 and powered by 9 V DC supply to the drivers' MV pins. Both motor drivers have their VDD (logic supply) pins ...
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84 views

Decoupling capacitor placements and ratings - how to choose?

I am building a circuit with 2 hybrid stepper motors each powered by a stepper motor driver A4988 and both drivers are connected to an Arduino UNO R3. Before soldering the components together on a ...
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1answer
79 views

Capacitor charging voltage showing ripples on scope. Origin?

I have an RC circuit delivering a square signal via a standard 555 timer set in monostable. I am powering the 555 with 4.88V DC directly from the Arduino, which itself is taking its power from the ...
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73 views

Mitigate parasitic capacitance coupling

First conceptually: Assume you placed two metal electrodes/tags on a fencer's body: one on the torso (large, the lamé), one in the hand (small, the guard). Equipped with a Capacitive Sensor located ...
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1answer
114 views

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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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 ...
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1answer
55 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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1answer
377 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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1answer
35 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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104 views

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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2answers
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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4answers
155 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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98 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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3answers
940 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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2answers
139 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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1answer
96 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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1answer
69 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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2answers
171 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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107 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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1answer
78 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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3answers
123 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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128 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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1answer
93 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
82 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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1answer
96 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
81 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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0answers
53 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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4answers
313 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
165 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
76 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
214 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
652 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
95 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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1answer
118 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
41 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
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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1answer
197 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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3answers
497 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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3answers
101 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
146 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
195 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
175 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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2answers
846 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
402 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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0answers
62 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
185 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 ...