Questions tagged [thermal]

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

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356 views

How do thermal tapes transfer heat despite their low thermal conductivity?

I found myself needing to attach small heatsinks to Mosfets and CC power regulators. Also some high-power diodes. Today I have learnt that thermal compounds, even best in the market, are dozens of ...
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3answers
94 views

Do unused relay pins help with heat dissipation?

I have been using DPDT relays to control high-current loads (~15 A at 240 Vrms) though I am only using them in a SPST, NO fashion; that is, the load is disconnected when the coil is de-energized, and ...
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2answers
48 views

Thermal noise voltage measured by an impedance matched ADC

I have a question regarding the thermal noise voltage measured by an impedance matched ADC. In the figure above, I have a simplified circuit with a source impedance (on the left) and an ADC (on the ...
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1answer
119 views

Will PCB board house accept this QFN thermal pad via design (KiCad)?

I am going to be ordering this board from JLCPCB which has some 0.2 mm hole diameter thermal vias on a QFN pad, and it says on their capabilities page that the smallest via hole size is 0.3 mm, BUT ...
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0answers
52 views

How to calculate MOSFET temperature increase in PCB

I want to calculate MOSFET(DATASHEET) temperature increase for PCB. MOSFET - FDD86250_F085-D Totally 13 MOSFET's will be mounted in PCB. At the same time, maximum 8 MOSFET's will be used in PCB 1, ...
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1answer
52 views

The Thermal relief consideration for TVS diode (for ESD protection)

I am designing a print which has some mircofit connectors, I have placed TVS very close to the connectors on the print and the ground pad connected with a GND polygon directly, this polyon connects ...
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3answers
50 views

Need help in cable temperature calculations

I am trying to calculate how hot will a 0.6m long 28AWG wire carrying a load of 12VDC, 0.2A get. I understand that are other factors such as environment cooling rate, thermal resistance between air ...
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3answers
32 views

Calculating Junction Temp of Switching Regulator

I was looking at TI web bench to find a regulator, my question is my calculation is correct and if it is why we have different value on webbench. The IC is TPS565208 P = (Vout - Vin)*Iout => (12-...
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10 views

Infineon IPOSIM tool for IGBT thermal loss calculations

I used the infineon IPOSIM power tool for simulating a motor drive for my required conditions and got the results for a custom input drive cycle. The results were given as power dissipation per IGBT(...
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1answer
35 views

Application based Heat sink design for Power diode

Instead of having a heatsink directly connected to the diode, I want to have a 2 mm layer of cold rolled steel in between case and heat sink(aluminium){for waterproofing as needed in the application}. ...
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3answers
197 views

Heatsink on underside of PCB

I have prototyped some DC-DC converter modules, and they work well. However due to size, I don't have a huge amount of copper pour for them to dissipate their heat. I have used 2oz copper but the ...
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1answer
50 views

Would leakage through a JFET create thermal noise

The impedance through the gate of a JFET is very high and leakage current very small. Would this impedance act like a large resistor creating thermal noise? Would this be a low noise way of ...
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1answer
52 views

Colpitts oscillator: how to reduce amplitude thermal drift?

I have built this circuit, supply ±12V: I am using a LM6172 amplifier. I have found the transfer function of the filter involved: \$H(j\omega)=\frac{1}{1 + \frac{R_3}{R_1} - L\omega^2(C_2+C_1\frac{...
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0answers
19 views

Heat transfer coefficient in a Module Baseplate

Today, for example in a power IGBT module cooled by a heatsink, it has been found that the heat transfer coefficient (htc) distribution may not be uniform across the bottom surface of the module ...
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1answer
29 views

Thermal resistance Junction - Maximum Power dissipation

I want to understand the real meaning of the parameter 'Thermal Resistance Junction to Air (°C/W) to calculate the power dissipation. So for example if the value of this parameter is 250°C/W, should I ...
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1answer
62 views

Resources for finding thermal impedances for common IC packages

I'm just looking for some extra resources for thermal impedances of JEDEC standardized packages. I've already found one such article posted by JRC, https://www.njr.com/semicon/package/thermal.html , ...
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2answers
86 views

Thermal Glue solvent

I have a PCB with many chips on it - it's a "hashboard" for an ASIC bitcoin miner. There are 63 chips on every hashboard, and each chip has a small heatsink on it. I tried heating the heatsinks with ...
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2answers
45 views

POWER MOSFET - Thermal Design

i have some doubts about with this thermal design? first, the calculations and infos: My load (a motor) uses an average current of 7A, I could not measure the current peak at the beginning of the ...
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1answer
40 views

Wire gauge and combined wires for 3D printer hotend through PCB

So I've been designing a wiring harness PCB for my 3D printer to provide connections and easily swappable tools. I settled on a TE 34-pin connector to use as input on the PCB. The current design ...
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1answer
60 views

LD1117V33 voltage regulator heatsink, thermal paste needed?

I want to screw a heatsink to my LD1117V33 voltage regulator. It's a normal 3mm screw and nothing inbetween. Do I need to use thermal paste or something like that? It will be regulating 12V down to 3....
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1answer
59 views

Water-Based Heat Sink

I am trying to incorporate a TEC in a portable system. The heat from the interior of the system needs to be transfered to the exterior where it can be dissipated freely into the environment. Now, I ...
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1answer
38 views

Cold activated heater control

I would like to build a simple control circuit for a 12v silicone heating pad. I think what I'm looking to make is a thermally controlled relay: I want current to flow when the temperature is below ...
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1answer
32 views

Circuit thermal analysis in PSPICE and temperature coefficients

I am tying to perform a thermal analysis in pspice. Resistors needs two temperature coefficients as TC1 and TC2 (if we assume linear change of R vs. T, it's zero) in pspice. But in resistor datasheets ...
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2answers
261 views

What is reasoning behind the common wisdom of limiting the temperature rise of a PCB trace to 5/10/20°C?

When deciding on the trace thickness required to carry a certain amount of current on a PCB, the answer depends on how much temperature rise you are willing to accept. This leads the designer into the ...
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2answers
85 views

Understanding the thermal images of planar pcb coils

Why is only the first turn in the coil hotter compared to other two turns? In this, only the turns of the top part seem to be hotter compared to the bottom. Current through the coils is 2 A. It is ...
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1answer
57 views

General Peltier-tivity

[EDIT: Found a couple of 12715 units in the pile that did suck the full amperage, but despite excellent cooling of the hot side, could not deliver much cooling.] I'm waist deep in project to keep ...
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1answer
35 views

Open-circuit alternator

Is it dangerous to run a permanent magnet alternator open-circuited? No current can flow so is all the power dissipated as heat? Is there even power generated in the inductive coils?
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0answers
33 views

Modeling the thermal part of the Time-current curve

G’ day, I am working on designing protection devices for my research work and I am struggling to model the thermal part for the low voltage circuit breakers based on IEC standards. Based on the ...
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1answer
59 views

Is there a difference between a tempco resistor and a thermistor?

That is, other than just the nomenclature.
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2answers
53 views

Temperature specificiations on MOSFET Safe Operating Area

Here's a SOA graph: What I don't fully understand is the notes area at the bottom: *Notes: Tc=25°C Tj=150°C Single pulse Every MOSFET datasheet seems to have a similar set of notes,...
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2answers
74 views

How do I determine the junction-to-ambient thermal resistance?

For a project I'm working on, I was considering using an AS7805 to supply low-noise 5V power to some sensors. (due to the uncertainty that resulted in asking this question, I've since changed to a ...
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2answers
869 views

LM317 - Calculate dissipation due to voltage drop

If I use a linear voltage regulator as LM317: Input voltage = 24 V Output voltage = 5 V (so a voltage drop of 19 V) Mean load = 480 mA (peak load = 700 mA) From the datasheet, I read that maximum ...
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2answers
36 views

Magnitude of \$I_{CBO}\$ in a typical transistor

I read in a book that \$I_{CBO}\$ doubles for every 10 degree rise in temperature and hence contributes to thermal runaway. However I am confused since essentially it is the reverse saturation current ...
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8answers
7k views

Why are electrically insulating heatsinks so rare? Is it just cost?

Edit: It seems my initial question (Why are there no insulating heatsinks?) was based on a false premise, and there are in fact insulating heatsinks--I just wasn't able to find them with a cursory ...
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2answers
68 views

Thermal calculation in case of duty cycle for a mosfet

For a multiplex LED matrix, I am intending to use two ULN2803's as sink source for 16 times 20 mA per column (channel). However, maybe I will try a test with 100 mA LEDs (10% duty cycle). For that I ...
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1answer
29 views

Thermal generation of electron-hole couples and reverse biasing

I'm studying the PN junction and I have some problems figuring out thermal generation of couples electron-hole in reverse biasing. The analysis is the standard one (for example, one can find it in the ...
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1answer
38 views

Macroscopic physical significance of Thermal Voltage in Diodes

Everywhere I search, the thermal voltage in diodes is described either as the microscopic property related to the average energy of electrons due to thermal motion The constant in the ideal diode ...
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1answer
50 views

How do I exactly calculate the amount of heat generated in MOSFET?

I am using two IRFP260N MOSFETs (datasheet) in parallel for my application. I am using it to drive a motor rated at 24VDC and consumes 8 to 10 Amps. I found some answers here and calculated the ...
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2answers
108 views

Why should the bias servo transistor not be placed on the main heat sink for a Sziklai pair?

The Wikipedia page on Sziklai pairs contains the following statement (emphasis mine) Sziklai pairs can also have the benefit of superior thermal stability. [...]. [Q]uiescent current is much more ...
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3answers
127 views

Cooling Methods for Voltage Regulators

I have a NCP1117 5V voltage regulator that is on an Arudino Mega. The Arduino Mega, with all of the necessary electronics parts for the project, draws around 200mA when operational. When using a ...
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3answers
442 views

heat dissipation in watts of equipment in a box

Here is the situation, some electrical equipment will be in low ambient temperatures and I need to make it warmer so that there is no damage to it. I want to calculate how much power in watts is ...
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0answers
37 views

Thermal Faliure of thermal overload protected ICs

I have encountered a number of instances now where ICs that supposedly include "thermal overload protection" will still heat up until they fry. Examples: LM338,LM2576. These devices datasheets ...
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1answer
62 views

Heating issues with solar charging circuit

I am using the above circuit to charge a 7.4V Li-ion Battery.With input MPPT voltage set at 12V, I have applied 13V input voltage to the circuit. The battery is charging at 1.4A. (according to the ...
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2answers
65 views

Does this circuit adequately represent the thermal considerations for a boost converter?

I'm new to electronics, and I'm trying to use a boost converter to get 5V at 1.2A from a lithium ion battery. I've selected the TPS61232 step up converter for this solution. The datasheet has a ...
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2answers
109 views

install heatsink on BJT

I am facing the problem with the heat of transistor disturb sensor reading. Here the link refer problem I am using BC548 transistor. It is a bit hot when operating because it disipates power around ...
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2answers
233 views

Shot or thermal noise of a MOS transistor

I'm trying to compare the shot and thermal noise contributions in a MOS transistor. In the literature, the above-threshold MOS transistor has only thermal noise, which is found by integrating the ...
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1answer
137 views

Control board powered up with reverse polarity. power transistor blown. Is this repairable? [closed]

My dog chewed through the power cord. I 'repaired' it not paying attention to polarity. It was a 2A, 9V wall wart type power supply. The motherboard is from an elliptical exercise machine. The one ...
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2answers
149 views

Wha't the difference to use the junction to case thermal resistance instead of the junction to lead thermal resitance?

In case I have a diode, and I want to know it could dissipate the power, I have two values, but I can't choose between them: - Junction to ambient thermal resitance \$R_{ja}\$ - Junction to lead ...
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3answers
753 views

How do electrons carry thermal energy in Peltier coolers?

I've read that when electrons enter from metal to semiconductor type N, they gain thermal energy and make that side cooler and the reverse happens when they leave semiconductor to the conductor. Why ...
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2answers
48 views

Am I misunderstanding steady state power disspation calculations?

I am looking at the Littlefuse 5KP series. It says on the datasheet: I am trying to understand how they arrive at \$P_D\$ = 8.0W. Given thermal resistances of 40°C/W or 8.0°C/W, and 100°C ...