Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [derating]

27 questions
15
votes
3 answers

Resistor surge rating

I have a circuit with a 220uF capacitor and a resistor is used to limit the inrush current I stupidly fitted the wrong power rating resistor and (no surprise it failed) its taken me a while to realise my mistake. I believe the correct resistor is…
Jamie Lamb
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What does derating mean?

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…
AKR
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9
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1 answer

How to derate a ceramic capacitor for DC bias

I understand that the capacitance of a ceramic cap is very dependent on the DC bias applied to the terminals. At rated voltage, I've measured a decrease of up to 70%, and I've heard it can go higher. That's two datapoints, one at zero voltage, and…
Jason_L_Bens
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8
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2 answers

Ceramic Capacitors vs DC Bias - Derating rule of thumb misleading?

Premise Ceramic capacitors with Class 2 dielectrics (such as X5R and X7R) usually show a reduction of its capacitance value as the applied bias voltage increases. This behavior is more prominent in higher density capacitors that feature high values…
FlyerDragon
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4
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1 answer

How do I derate paralleled diodes with negative temperature coeffecients?

In my application, my load current is 1.4 amps, and for reasons of cost, availability, and recovery time, I want to use this particular 1 amp diode. Like many diodes, this one has a negative temperature coefficient; the hotter they get, the lower…
Stephen Collings
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2 answers

Have bypass cap recommendations already taken derating into consideration?

Datasheets often specify specific values for bypass caps. My assumption is that these values reflect the actual value (after derating), however, I often see on evaluation boards the same nominal value components being used. X5R caps can lose up to…
mhz
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3
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2 answers

LED limit to short pulse and high power

I’m studying the viability of a small footprint distance detector that relies on a LED, a photodetector and some lenses. It’s meant for a distance above 150m, where the light beam travel time is higher than 1us. Although the 1us time is within…
PDuarte
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6 answers

Filters: what kind of capacitor?

Until recently, I (foolishly) believed that the capacitance of a given capacitor was the capacitance given by the datasheet +- the tolerance. I recently learned about the DC derating of MLCC (multi-layer ceramic capacitors), which can be quite huge…
Sandro
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2
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1 answer

X5R capacitor derating and highpass filters

X5R capacitors derate to about roughly 85% when DC voltage is applied, from what I have been told. Does this have an effect on high pass filters, even though HF filters off DC (0Hz)? If I wanted to test voltage derating on capacitors and its effect…
Vinh Trung Thai
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2
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1 answer

Correct LED derating

I am currently looking at the datasheet of a LED and have snipped out the passage of interest. The question is how do I find out the intensity I can reach at a specific temperature/current by using the these curves? Assuming I have an high ambient…
Junius
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1 answer

For calculating inrush current in a ceramic capacitor , do we need to consider the effective capacitance after derating for dc-bias effect?

Inrush current happens when capacitor is initially charged from 0V to the intended rail voltage. What should be the effective capacitance to be considered during this charging? -Since the voltage keeps on varying and effective capacitance for a…
Divya K.S
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2 answers

Zener temperature derating

Can someone explain what the Ta line on this zener diode temperature derating graph means please. The diode is an MCC SMBJ5338B 5.1V 5W zener. I understand the lead temperature (TL) line means derating linearly above 75°C but the ambient…
PhilS
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2 answers

How fast do tantalum capacitors self-heal?

I am troubleshooting a design that uses a 47 µF 20 V tantalum SMD cap across a 15 Vdc rail. While the derating guidelines I follow dictate a 50% voltage derating for tantalum caps, the design I'm looking at slipped through the cracks, and 15 Vdc is…
Bort
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3 answers

EEE-INST-002 Wire Derating - Single Wire vs. Bundle/Multi-Conductor

We have an aerospace application and are having trouble defining EEE-INST-002's current derating guidelines in regards to wire. The issue that I have isn't about stranded versus solid. MIL-W-22759 does seem to classify tinned, copper strands as one…
depwl9992
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1 answer

Using a COTS common mode choke on DC

Are commercially available common-mode chokes, such as one you'd pull out of a dead switching supply, suitable for DC service up to their rated current, or will they saturate/do other baleful things when subject to their rated current as DC instead…
ThreePhaseEel
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