Questions tagged [thermal]

Relating to temperature rise, the flow of heat, or cooling of components

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Can a CPU heatsink be used to cool a TO-3P or a TO-220?

I want to know if my thermal design is appropriate for dissipating 72W of heat while keeping the junction temperature below 150 °C (I am trying to cool an SFH154 that comes in a TO-3P package). My ...
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Is this avalanche rugged MOSFET suitable for linear operation?

I would like to create an active load which draws current(4 to 6A) from a 12V battery. Unfortunately, the shipping costs and delivery times have prevented me from buying Linear FETs directly from well ...
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Is this IRF9640 MOSFET operating within the recommended temperature as specified by the datasheet and why is it so hot?

There's a handful of questions already asked about the differences between operating temperature and ambient temperature for electronic devices, but my question is specifically for the irf9640 MOSFET ...
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All Mosfet terminals internally shorted in voltage controlled resistor

I was planning on making a voltage controlled resistor using a power MOSFET in order to load one 12V lead acid battery. I tried implementing the circuit below; everything was going well for a few ...
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Layout for MOSFETs (copper area for source vs drain)

I have a schematic. Here is a section of it: The FETS are being driven by the chip to behave as ideal diodes. Plus two FETs in series to block current path when chip is in shut down stage. I've seen ...
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Risks of exceeding current discharge rating of a LiPo battery

I have a project that consumes a maximum current of 1.6A, that requires the use of a small LiPo battery. I have one that has the perfect size, but has capacity of 400mA, and a discharge rating of 1C (...
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2 votes
1 answer
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PWM Controlled Resistance vs Resistor to minimize heat dissapation

I have a low-ohm resistor (7.5 ohms) connected to a MOSFET used for passive charge balancing. It is generating a lot of heat on my PCB. I can apply a duty cycle to the switching which somewhat combats ...
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2 answers
39 views

Inconsistent diode and MOSFET power rating

I’m trying to design a power supply for an electromagnet. For this, I’m using a Buck topologie in which the electromagnet is the coil. The voltage comes from a 400V PFC. Required current is 8 Amps (...
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2 answers
241 views

BJT collector power limit in pulsed usage?

Assuming that my circuit respects the voltage, current, and thermal limits of a BJT, can the device be electrically damaged by exceeding an instantaneous collector power limit? In other words, are BJT ...
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How to calculate specific heat capacity of film and electrolytic capacitors?

I am trying to build a thermal equivalent model of a capacitor and its ESR in Simulink. I know the heat flow rate going into the capacitor, as well as the thermal resistance value, but I am missing ...
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Which is better, the MB10S or the MB10F?

I am replacing a blown MB10 rectifier IC on a small LED power supply. The letter could not be read anymore so I don't know which one to get. The S or the F variant. In the datasheet the electrical ...
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Is the generator inside thermal power plants a synchronous type or asynchronous one? [closed]

Are thermal power plants connected to the electric power grid based on synchronous generation or asynchronous one? If a mix, which is the main one?
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1 answer
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UDFN Package, exposed thermal pad - to ground?

So I've got a design in which I would like to use the AT25SF321B-MHB-T chip by Dialog Semiconductors, but its datasheet does not mention whether the exposed thermal pad should be connected to ground ...
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Thermal equivalent circuit models

When I only have two components (for example a Module and a heat sink), what thermal equivalent circuit models (Cauer or Foster) should I use to represent it?
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-3 votes
3 answers
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Why does the LM7805 heat up? [duplicate]

I'm really not comfortable with things heating up, including this LM7805 integrated circuit wired below. Why does this mighty LM7805 heat up? Thank you for the help!
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Where does all the electric energy get dissipated in any electrical system?

I know that some portion of the electrical energy is dissipated as heat due to the efficiency, but where does the other energy go? If we are talking about a satellite in space, all of the electrical ...
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How do you install a thermal fuse in a hairdryer?

Is it possible to manually wrap the thermal fuse's pins around the 'grommets' as shown in the picture? The arrows point to the two grommets, with the thermal fuse in the question across the top.
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Thermal dissipation on TO-252-3 Package

I am in the process of designing a surge stopper with fault latchoff using LT4356. https://www.analog.com/media/en/technical-documentation/data-sheets/LT4356-3.pdf I decide to use this MOSFET, which ...
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How to I optimize this LED circuit?

The Project This part is pretty simple: I'm building a stunt lightsaber up from scratch. The led is held in a heatsink housing inside a 1 inch (internal diameter) aluminum tube. The heatsink is rated ...
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1 answer
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SMD "power" resistors : what constraints on PCB layout

I'm looking for current sens resistors. As those are rather big (and beeing for now the limiting element for my PCB size), I would like to stop using over-rated one and take some with "just" ...
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Possible fixes to a power supply thermals issue

The question applies to a buck converter design on my board: Here is a 3D view of this section: Layout of this section: L1: L2: Layer 3 is power and layer 4 is again a full ground plane. Here is ...
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1 vote
2 answers
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How to use units given for heatsink thermal resistance?

In looking for a heatsink I came across a company giving the thermal resistance of extrusions in °C/W/3in. How do I use this? Say I use an extrusion with a specification of 1.5 °C/W/3in and get it ...
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1 answer
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Thermal noise typical values

I am curious to know what thermal noise waveforms look like in the time domain. Most of the analysis is based on probability. What is the typical voltage amplitude of thermal noise in let's say a ...
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Why is the thermal conductivity of FR4 shown to have two different values? (Based on heat flow direction)

Reference Why would thermal properties of a material (FR4) depend on direction of heat flow?
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Estimation of Rth(ja) when not provided

I am looking at the datasheet of a SiC MOSFET, which has a junction to case thermal resistance Rth(j-c) max of 1.41°C / W. The junction to ambient thermal resistance is not provided, as this type of ...
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Heat sink thermal resistance

Is there any way to figure out the thermal resistance of a heat sink without using a datasheet or using it in an actual circuit? I mean, simply by knowing its dimensions and material.
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-1 votes
1 answer
66 views

Heatsink size calculation

Let's say I found a random heatsink with no name or model or anything else from which I can find a datasheet and get its thermal resistance. Therefore, simply by knowing its sizes, how can I calculate ...
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1 vote
2 answers
79 views

Will mounting the hub of a fan directly above a heatsink have a big impact on thermal performance?

The 6 SMD MOSFETs in the center generate a total heat of about 80w. I was planning on using this heatsink (ATS-1106-C1-R0) with this fan (08025SS-24Q-AT-D0) mounted directly above it. Looking at the ...
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59 views

How much thermal headroom?

How much headroom is good design practice for a junction temperature calculation? If a junction can be max. 150°C for example, what is the closest temperature one can be under and still feel "...
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Procedure when taking thermal (IR) imaging

I am a junior electrical technician. This question is not on theory but on the practical procedure of how to take a thermal imaging on an electrical switchboard. I will appreciate if some veteran ...
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1 answer
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Running load directly off solar panels (bypassing charge controller) - Silicone heater

I am working on a solar setup that is powered by a Li-ion batteries. However, Li-Ion batteries can't be charged below 0 deg C, and thus if it dies in the winter, it will need to be warm before it can ...
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Impact of heat on unshielded data cables

How does heat impact the signaling performance of unshielded ribbon/flexible flat cables? Background: I'm modding a camera to improve thermal performance by adding thermal pads between the heatsink ...
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1 answer
165 views

Thermal vias-in-pad - leave bottom side tented or exposed?

What is the suggestion for thermal vias under the exposed pad of ICs ? I understand that copper plugging would be ideal. But if I only have the choice of tenting or not tenting, should I leave the ...
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Using Thermal Epoxy vs Super Glue for Thermal Couple temperature measuring

Which practice is better for measuring the temperature if a MCU on a PCB with a thermocouple: Measuring on the case of the MCU with thermal epoxy attached to the thermal couple, or super glue? I feel ...
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72 views

PCB via array for "better" heat dissipation

My two PCB mount power supplies are getting quite hot (temp 60 to 70 degrees). Max temp of the power supply is 90 degrees. I cannot use external heatsinks due to space constraints. Input voltage is ...
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1 vote
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50 views

Cooling 1.5 cu ft with a TEC1-12715 Peltier

I'm trying to modify a standard cooler (about 1.5 cu ft) so it no longer requires ice. I want to get the interior to 35 - 40F assuming the ambient temperature is about 75-80F. However, I don't have ...
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1 answer
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Way to handle rapidly changing current demands and excess heat

So I have a circuit like this: And I am driving it with a desktop power supply at 5A (<1 Volts varies by coil). The issue that I am having is that my power supply is overheating. I am rapidly ...
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-1 votes
4 answers
157 views

What is bandwidth here?

The voltage(rms) created by thermal noise is: What is the bandwidth(Δf) of the thermal voltage?
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1 answer
62 views

How should fuses be used for MOSFET temperature protection?

I am using high voltage MOSFET in TO-220 package with a heatsink like this one: Under normal conditions, the temperature of heatsink does not exceed 90 degrees. My MOSFET can run up to 120 degress ...
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3 answers
116 views

Heatsink needed to keep my resistor from damaging due to heat

I am looking to find an appropriate range of heatsink selections to maintain my resistor from damage due to heat. I am using a flat plate (SS) resistor from ARCOL (TFBR900). It is rated for a 900 ...
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1 vote
1 answer
84 views

How to estimate thermal impedance of a closed aluminum chassis?

I am contemplating whether or not I need chassis perforations for heat dissipation in a project. The box is roughly 440 mm wide, 280 mm deep and 85 mm high (2 rack height units aluminum enclosure.) ...
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12 votes
4 answers
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Why are these SMD heatsinks designed to not touch the IC?

I am using a 7106DG heatsink to dissipate the heat from an IC. It looks just like in its datasheet: It leaves a gap between the IC and the heatsink, and the datasheet even mentions it, but I guess no ...
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1 vote
1 answer
70 views

Thermal protection of triac in floor heating controller

Hello there fellow engineers. I'm in the middle of design controller for floor heating. The idea is to have a triac based design with zero detection circuit, for each control point (each heating cable ...
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1 vote
1 answer
69 views

Copper Weight/Copper Pour Usability in Thermal Management

I'm trying to think of a way to decrease the temperature that my PCB is running at, but I don't want to add a heatsink if I don't have too since I want this board to have as low of a profile as ...
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2 votes
3 answers
172 views

How does junction to case thermal resistance depend on PCB?

Shouldn't the junction to case (top or bottom) thermal resistance depend only on package or IC internals? How do the PCB details play a role as mentioned in footnote 1?
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6 votes
2 answers
834 views

Why is the thermal resistance of copper shown higher than FR4 in below snap?

I see similar W and L for both Cu and FR4. Why is the Cu thermal resistance shown higher than FR4? Is it because of Ounz difference? 1 Oz Copper= 34.8um. FR4 seems to have more thickness-> How ...
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  • 2,051
2 votes
0 answers
58 views

Silicon die on Peltier device with COB wirebonding

I have a camera sensor (bare die) that must go on a very tiny PCB that also contains electronics for data serialization that dissipate enough power to make the PCB pretty hot (40-60 deg. C). I want to ...
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0 votes
1 answer
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Component identification in a thermal device [closed]

I have a picture of a device's handpiece and I want to know the applicatioan of its components but I'm confused about one of them. Can anyone help me to figure out what this is component? (Marked with ...
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1 answer
67 views

Wire heating from microwave signal

How would one calculate the temperature change in a wire into which a microwave signal of a given frequency and power is applied?
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2 votes
5 answers
133 views

Cold start heaters for PCBs

I am working on a custom PCB design. The SoC chipset which we use supports only commercial grade temperature (minimum operating junction temperature of SoC chip is 0ºC.) We want to operate the device ...
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