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Questions tagged [thermal]

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

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2
votes
1answer
1k views

Thermal noise (Johnson noise)

Let's say there's some 50 ohm resistor connect across the input of some 2 port network that has an input impedance of 50 ohm, so like this: simulate this circuit – Schematic created using ...
2
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3answers
388 views

Do I need to use thermals on vias for reliability?

This question is further to Why thermal reliefs on vias? I have recently been advised (by someone I consider an expert) that I should add thermal reliefs to vias which are connected to planes, even ...
1
vote
1answer
277 views

PCB Board design for H-Bridge TLE5206

I would like to make PCB board for TLE 5206-2G (check the datasheet). It is TO263 package. Basically, what i dont know is how to transfer heat out of the IC. I saw few PCB's that has little copper ...
7
votes
1answer
566 views

How can SCRs be effectively paralleled?

I'm designing a precharge circuit which will carry 200A when closed. I'd like to use MCO150 Silicon Controlled Rectifiers, but they won't handle the current. Two in parallel looks like the most cost-...
4
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2answers
117 views

Thermal relief style X or +?

Is it there any differences between a thermal relief in a 'X' shape for a '+' shape? I am using Altium and the software has boths styles for selection.
5
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3answers
7k views

MOSFET heat calculation question

I am using the FQP30N06L MOSFET: http://www.fairchildsemi.com/ds/FQ/FQP30N06L.pdf. As far as I understand the data sheet, if I connect 5V to the gate and run 2A through drain to source then with a \$...
0
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1answer
2k views

How to understand this label on part?

From the label on thermostat I can read the following, but can't decode it to understand the max current. CAMPINI Ty 95 C1-16(3)/250~ C2-6(1)/250~ Does ...
1
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2answers
1k views

What happens when I connect the GND of a LDO in a Diode to the real GND?

A friend of mine told me to put a diode between the LDO's GND pin and the circuit's GND. He said the LDO will regulate it's fixed voltage plus the diode drop. Is it true? How does it work? I am using ...
6
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3answers
5k views

SOT-223 Thermal Pad and Vias

I am using a LDO with a SOT-223 footprint and since it might get hot, I wanted to make a nice thermal pad under it to dissipate that heat. I googled and I only found thermal pads, but i wanted some ...
5
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2answers
2k views

How to calculate a PNP transistor thermal dissipation?

I am working with a dual power circuit for using USB and a LDO at the same time with a PIC18F2550. The circuit is the same as the one in the PIC's datasheet. My question is: How do I calculate the ...
3
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2answers
3k views

Do Thermal Cutoff switches exist for temperatures below 50 C?

I have been trying to find some passive thermal cutoff switches for a project, but it seems that all of them are for 65 degrees C and up. Is there another name for lower temperature TCOs? Any help ...
3
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2answers
3k views

What are thermals?

I was looking through various options available for Eagle CAD through-hole and SMD pads and I noticed a "thermals" option. The documentation wasn't much help in determining their function other than ...
6
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3answers
1k views

Apparent inconsistency of MOSFET power rating in datasheet: SOA v. max power

I am trying to use an IPP114N03L G (datasheet). I calculated the maximum power it could handle as follows: From the first two pages of the datasheet: Rthjc = 3.9K/W Tj(max) = 175C Assuming I can ...
3
votes
1answer
366 views

LM3876 Heatsink

Could someone point me to a suitable heatsink for an LM3876 amplifier? Or, even better, a heatsink that I could attach two chips to? Perusing through Mouser's catalog was a bit overwhelming. ...
4
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2answers
5k views

Thermal management of MOSFETS in TO-263 package

I'm using SUM60N02 MOSFETs in TO-263 package for my car battery charger power unit. In datasheet they have specified thermal resistance: Junction-to-Ambient - 40 °C/W when mounted on 1" square PCB ...
7
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4answers
1k views

Can I create a backside “copper polygon” of the switch node in an SMPS?

I have an SMPS design that has the following properties: 9-15V input voltage 5V, 3A output Switching frequency is 350kHz. Switching controller is a LM25085. The diode used is a DSSK48-003BS. The ...
6
votes
1answer
2k views

Generating thermal noise from a resistor

I'd like to create a random number generator based on thermal noise from a resistor, using an opamp to amplify the noise and an inverter to convert the resulting spikes into a digital signal. Here's ...
28
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4answers
18k views

How do I determine the area of copper needed on a PCB to provide adequate heatsinking for a power SMD MOSFET?

I am planning to use the IRFR5305PBF Power MOSFET (http://www.irf.com/product-info/datasheets/data/irfr5305pbf.pdf) to switch on a load. I have determined that I need an external heatsink with Rthsa &...
1
vote
1answer
9k views

Are thermal fuses polarized?

I have a device with a thermal fuse in it. The fuse has failed, and I would like to replace it. Does thermal fuse have a polarity, similar to an electrolytic capacitor, or is it the same with normal ...
6
votes
1answer
1k views

How to correctly apply thermal compound to ICs and heatsinks?

From http://en.wikipedia.org/wiki/Thermal_grease All these compounds conduct heat far better than air, but far worse than metal. They are intended to fill gaps that would otherwise hold air, not to ...
4
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1answer
2k views

How to design high-current through hole solder connection to large planes

We have a power connector, which is capable of delivering 20Amps to a PCB. On the PCB, one layer is dedicated to Vdd, which is 5V. The board is quite large, 200mmx300mm. The power connector is ...
4
votes
3answers
12k views

TO-220 case-to-sink thermal resistance

I'm using a KSC1173 TO-220 power transistor in a design, and I need to calculate the case temperature for the maximum average power dissipation, to see if the power dissipation falls under the ...
4
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5answers
6k views

Heat transfer in an airtight enclosure (component -> internal ambient -> heat sink on case?)

Are the thermal resistance values of heat sinks/etc reasonably reversible? If I wanted to dissipate an internal ambient temperature rise, could I use an internal heat sink on the enclosure wall ...
5
votes
1answer
190 views

How does a high voltage condition break down a semiconductor?

I have TVS diode in parallel with circuitry for ESD/lightening/transient voltage protection. Say I receive an over-voltage condition which is beyond the specifications of the part, what happens ...
4
votes
1answer
1k views

Powering electronics with a low-cost thermoelectric generator?

When I replaced my water heater, the installer was telling me how cool the Bradford White unit I got was because the electronics are powered by the same heat used to heat the water in the tank. I ...