PT54 Help

[justinjja]

In the datasheet the max junction temp is 80c

I found the Leds on chip Thermistors B value to be ~3400
and its 25c resistance is 10k omhs

Based on that I can find the Thermistor temp

But I couldnt find a (Degree/Watt) number
connecting the Thermistor temp to the junction temp

any ideas?

http://www.mouser.com/catalog/specsheets/pt54phlatlight.pdf

 

[Meatball]

You need to know three data points, which are given here in the NTC datasheet:
Search Engine | ?????
^^Translate into English if necessary

You use the appropriate constants in this lovely little gem:
Steinhart?Hart equation - Wikipedia, the free encyclopedia

You could also just collect those data points yourself and use an online calculator:
Steinhart-Hart Thermistor Calculator
Thermistor Calculation Examples
Capgo - Thermistor Calculator

This is a really nice one: Calculators for Temperature and Thermistor Applications

Check out the section titled "B or β parameter equation"
Thermistor - Wikipedia, the free encyclopedia

^^I think the datasheet has everything you need to use that simpler linear approximation.

That should give you a push in the right direction.

 

[justinjja]

Thanks, but that all deals with the thermistor,
I need info on the LED
Most devices like this LED would have a rating that relates the case and junction temp in relationship to wattage

EDIT:

Found it on the Luminus webpage,
1 degree c/w

 

[Meatball]

Oh. Ermmm.

I missed that whole "junction temp" bit. Sorry about that.

Good luck on your project!

 

[BShanahan14rulz]

Specification | Murata Chip NTC Thermistor Output Voltage Simulator | Murata Manufacturing Co., Ltd. go here for info on how to use murata's characterization tool for NCP15XH103J03RC.

page 6 on the datasheet you linked shows the thermal resistances between the points of interest. It also gives you an R0j-ref, were thetaj denotes junction and ref denotes reference point. This is the thermal resistance between chip and thermistor location, and I believe is in the units you are looking for, at 0.94.


edit: I see you found already, that it is ~1.

 

[justinjja]

Specification | Murata Chip NTC Thermistor Output Voltage Simulator | Murata Manufacturing Co., Ltd. go here for info on how to use murata's characterization tool for NCP15XH103J03RC.

page 6 on the datasheet you linked shows the thermal resistances between the points of interest. It also gives you an R0j-ref, were thetaj denotes junction and ref denotes reference point. This is the thermal resistance between chip and thermistor location, and I believe is in the units you are looking for, at 0.94.


edit: I see you found already, that it is ~1.

Actually you are right it is .94,
Somehow I missed it the first time I went through the datasheet

+1

 

[BShanahan14rulz]

Sounds like someone's gonna be driving one of these to its limits :eg: