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44 Threads found on Thermal Junction
Crrs @ 24V doesn't give the effectiv capacitance, due to non-linear characteristic. You better use plateau charge from Qg graph. Expectable rise/fall time is about 100 ns according to my calculation, switching loss about 0.5 W, still moderate. junction-to-ambient thermal resistance of 62 K/W demands for heat sink, e.g. a small PCB mounted type
Hi Could someone please help me with a problem. I have a PCB that fits in an ABS box and is to be completely potted, top and bottom. I am investigating device failure modes, as I need to ensure that the outside surface temperature does not reach 135C. I've worked out that one SOT23 device may reach a junction temperature of 150C, under fault
Max junction temperature = 150*C, use 120 for safety. Tambient = 40 *C, so you have to dissipate 10 Watts across a temperature of 110*C. The thermal resistance of the junction to case is 6.5*C/W, So the case of the transistor will be at 65*C less then the max, i.e. 120- 65 = 55*C. So the heatsink will have to dissipate 10W with a temperature (...)
The junction-to-ambient (j-a) thermal resistance figure you cited is for a device that relies on its own body surface to dissipate heat to the surrounding air. The small body is rather inefficient for the job. Any device that has to dissipate appreciable power is supposed to be mounted on a heatsink. Depending on the power level, the heatsink may b
Hello everyone, I am doing thermal Analysis of my device and I need to calculate thermal resistance between junction and Case of my device. All I given in datasheet is junction temperature and Base plate temperature. There is no information given about thermal resistance between junction (...)
Hello. I have for the last two years almost been active in regards to scavenging electronics components from any device which contain any electronics, and I have a plastic basket sort of thing at home that soon will be full of heat-sinks. I want to characterise them in some manner in order to gain a at least ball-park estimate of how much th
You could ask "which junction?"; often the power dissipation is localized, not uniform, and die-scale calculations from uniform heating are not accurate or useful in predicting reliability or electrical effects of thermal rise at the hot spot. While a power device of the simplest sort may have only one, two junctions closely coupled, ICs (...)
Enclosed cases are always critical thermal designs. Apart from having to use a large fan to ensure equal distribution of air flow through the greatest possible internal surface of the cabinet, it may also be necessary an additional small fan over the hottest components in order to prevent the junction temperature exceeds the specified limit.
Work out how much power the transistor is going to dissipate. Look at the data sheet and find out the thermal resistance between the junction and case. This will be in the form of degrees C per watt. So multiply the power and thermal resistance together. This then gives a figure of how much hotter the junction will be then (...)
They most likely test everything in 0.1mS to prevent zero Tj thermal rise. 100ms is too long for this low mass 1sq mm part. When they say Ta, they also mean Tj. Thus 10 repetitive measurements could be made with 0.1% duty cycle in 1 second. But it is up to them if they want to measure 1, 2 or 10 or more times. I just read that the [URL="http:
Hello, We have a 510W switch mode LED driver PCB (three 170W channels) and we cannot mount it on a heatsink a there?s no room in the enclosure for a heatsink. There?s also no room for fans in the enclosure. Also, we cannot have vents in the enclosure sides. In order to try and make the thermal situation for this SMT PCB as best as possible, w
All 78xx regulators has an internal thermal shutdown if the temperature gets too high. This is an emergency shutdown, and acts as a safety measure. The thermal resistance from junction to air is around 60 C/W, so it means that you can have less than 1.5W disipation from a chip with no cooling. For an output of 8V from a 24V supply you (...)
Yes. On-state voltage is about 1V, power disspation 3.5W, thermal resistance junction-to-ambient 60K/W => Δt 210 K
Heasink temperature is not the concern.Instead, junction temperature should be considered. By doing a backward calculation, you can find the junction temperature if you know thermal resistances of Heatsink to Package (including insulator,mounting plastics,other mechanical parts etc),Package to Die,Die to junction. The (...)
Both thermal resistances are in series, i.e. have to be added.
is the average gate power dissipation what determines how many W it can handle? Not at all. Gate power dissipation will be small in a reasonably designed circuit. It's total power dissipation, thermal resistance, maximum triac and ambient temperature that sets the maximum current. junction to free air thermal resistance is respo
The datasheet says: thermal Resistance junction −to −Ambient (Note 2) is 68C/W When mounted using minimum recommended pad size on FR −4 board. The package is DPAK CASE 369C−01. What does the "minimum recommended pad" mean? Does it mean I don't need to place th
I want to better understand the nature of the increase in npn collector current with increasing temperature. For Vbe held constant we know that this current approximately doubles with every 10 degree C increase in temperature. I believe there are two sources of this current increase and that they add to each other (they are in the same directio
The BTA series has a higher junction-case thermal resistance due to the internal isolation, but that's compensated for by mounting the device on a heatsink without an external insulator. If the load is low enough that a heatsink is not needed, then the small difference in junction-ambient thermal resistance should not matter (...)
Vishay has a thermal SPICE model to calculate the dynamical junction temperature. AN609 is explaining the method They have also a thermal simulation tool, but I didn't use it yet.