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Derating as the Wiki and other Google articles says operating the part at lower values than rated specifications to prolong its life.

  • Can some please explain "What exactly is Derating?"
  • How it is related to positive and negative temperature coefficient.
  • Derating is limited to only resistors and capacitors or it applies to ASICs also.

I know the question which I am putting here is like dots and expecting someone to connect them for meaningful information. But this is the only information I have now.

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Can some please explain "What exactly is Derating?"

Operating the part at lower values than rated specifications

How it is related to positive and negative temperature coefficient.

Running a part at a lower voltage or current means less heat is generated. Powering a 16v max capacitor, at 16v, is stressing it. Running a 20mA led at 20mA will only provide x number of hours of life, while running it at 10mA will provide y hours, where y is greatly larger than x.

Derating is limited to only resistors and capacitors or it applies to ASICs also.

Derating can apply to almost anything. Resistors, LEDs, Other Diodes, Capacitors, ICs, CPUs. Another common word for derating, in the context of computers and CPUs, is underclocking. As opposed to overclocking, where you run a cpu at a higher than rated speed, underclocking (aka derating) runs it at a lower speed, allowing for less heat and longer life. Mainly used when modders want to remove noisy fans.

As a note, some devices demand derating in certain situations. Resistors listed as x wattage, expect the resistor to be in free air at ambient temperatures with air movement over it. If you put it in a sealed case, or in heat shrink, or in a hot environment, you NEED to derate it down. Same with Solar Panels. The given rating is for IDEAL sunlight. Average sunlight will derate the output current and voltage.

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  • \$\begingroup\$ Can you please explain how the second answer relates to positive and negative temperature coefficient? \$\endgroup\$ – AKR Nov 3 '13 at 11:45
  • \$\begingroup\$ sorry I dint get you.. \$\endgroup\$ – AKR Nov 3 '13 at 11:52
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Can some please explain "What exactly is Derating?"

To derate is to take some operating rating and lower it to produce a safe/acceptable operating rating based upon other factors.

http://www.farnell.com/datasheets/1720486.pdf Take a typical SM0805 resistor. 0.125W power dissipation.

The datasheet states: 100% power rating upto 70C and then linearly de-rates to 0% at 155C

ie if you were to operate this resistor at 155C then it would only be able to dissipate 0W (ie it won't work).

Now some places then provide additional derating guidelines on top of manufacturer derating to improve product reliability.For a resistor is would include power and voltage rating

How it is related to positive and negative temperature coefficient.

In a similar way. Where the temp coef comes into play is when you do any form of stress calculations.

1) you determine the maximum operating temperature (with some margin I would hope)

2) you work out the spread of resistance due to tolerance ( 10k 1% tol ==> 9k9 & 10k1)

3) you determine the additional variation due to temperature. THIS may increase or decrease the resistance due to it being a PTC or a NTC.

Determine the power dissipated. Compare this to the maximum for the package including manufacture derating and any additional derating.

Derating is limited to only resistors and capacitors or it applies to ASICs also.

It covers pretty much everything (and not just electrical). Some of the things I concider

Discrete Semi: Junction temp re-rating Resistors: Power stress, Voltage stress (DC and transient) Capacitor: Voltage stress, Power stress Diodes: Power stress, blocking voltage stress, forward current Zener: Power stress MOSFET: Vds stress, Vgs stress, Power stress, drain current stress

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Can some please explain "What exactly is Derating?"

You gave the answer yourself: "operating the part at lower values than rated specifications to prolong its life". Is there anything that is unclear to you in that sentence?

How it is related to positive and negative temperature coefficient.

Without a specific component and application in mind, this is impossible to answer.

Derating is limited to only resistors and capacitors or it applies to ASICs also.

It applies to everything, including for instance mechanical and chemical components.

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  • \$\begingroup\$ Is it all the specifications of resistors like operating temperature, power like 1/4 or 1/8 etc. or anything else. Please assume components to resistors and capacitors for positive and negative temperature coefficient. \$\endgroup\$ – AKR Nov 3 '13 at 11:42

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