What Are Good Alternatives for PTC Thermistors with Sharp Resistance Changes?

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SUMMARY

The discussion focuses on alternatives to PTC thermistors for high-power electronic systems requiring a hardware shutdown for over-temperature conditions. The user, Sparky, seeks components with sharp resistance changes and expresses dissatisfaction with the limited options from EPCOS, particularly regarding tolerance and nominal values. Suggestions include exploring bimetal switches and the LM57 temperature sensor from Texas Instruments as potential alternatives.

PREREQUISITES
  • Understanding of PTC thermistors and their applications in temperature sensing.
  • Familiarity with resistance vs. temperature characteristics in electronic components.
  • Knowledge of tolerance specifications in electronic components.
  • Basic concepts of hardware shutdown mechanisms in power electronics.
NEXT STEPS
  • Research alternative PTC thermistor suppliers beyond EPCOS for better tolerance options.
  • Investigate the specifications and applications of bimetal switches in temperature control.
  • Learn about the Texas Instruments LM57 temperature sensor and its suitability for high-power applications.
  • Explore digital signal processing techniques for integrating temperature sensors into electronic systems.
USEFUL FOR

Electronics engineers, power system designers, and anyone involved in thermal management solutions for high-power electronic applications will benefit from this discussion.

Sparky27
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Hi all, I'm new here so I thought I'd give this a shot.

I'm developing a relatively high power power electronic system and I want a hardware shutdown for over-temperature without going back and revving my PCB too extensively. One effective way to accomplish this is with a PTC with a sharp Resistance vs Temperature characteristic like so:
upload_2016-3-31_10-7-26.png


I've actually purchased this kit shown here: http://en.tdk.eu/inf/55/db/PTC/PTC_Sensors_SMD_chips_standard.pdf

I'm still shopping around but I'm wondering if any of you have experience with PTC selection. Here are my main issues:
1. NTC's generally won't work for what I'm trying to do because they are relatively linear. Effectively what I want is a temperature triggered switch (like shown characteristic). The linked above was the only family of resistors (EPCOS) that I could find with that property. Does anyone know of any other manufacturers or kits that might have this feature?
2. The tolerance range of these ones I've found is HUGE (+/-50%). This will become a digital signal at the end of the day so I can work with it but I'd prefer less slop. Once again, does anyone know of any other suppliers I can go to that will have a better control on tolerance?
3. The nominal values from this kit are very limited (just 110, 470,680,10k) and I'd like more options.Basically, I'm still shopping but thought I'd give it a shot in case any of you out there know your PTC's and more importantly your suppliers.

Thanks!
Sparky
 
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Sparky27 said:
One effective way to accomplish this is with a PTC with a sharp Resistance vs Temperature characteristic
A bimetal switch could be an alternative.
It's simply on/off.
 
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