Dave wrote on 11/8/2019 11:17 AM:
I think I figured it out enough to make sense of it. The 1.5 ohms will likely be the normal state and if a short occurs the resistance will quickly rise to the 10 ohms and trip the PTC fuse. That works for me. The reason I was worried a little is that the resistors I use in the circuit range from 5.1 to 10 ohms and that could have caused me some re-design issues.
Thanks,
Dave
On 11/7/2019 6:46 PM, Dave wrote:
In reference to the part number 1206L010/60 (second one down in top list), I have a question.
Resistance R (min) = 1.5 ohms
Resistance R (1max) = 10 ohms
R min = Minimum resistance of device in initial (un-soldered) state.
Rtyp = No spec given.
R 1max =? Maximum resistance of device at 20°C measured one hour after tripping or reflow soldering of 260°C for 20 sec.
Hello, Dave--
I haven't located an app note for the Littelfuse part, so what follows is
guesswork. I interpret the specs as defining the resistance prior to exposure to an
overload to be 1.5 ohms or more (Rmin=1.5 ohms).
The spec defines? R(Imax) as the resistance measured one hour after the device is
exposed to its maximum overload current and thus self-heated? to some unspecified
temperature. (The reflow-soldering process will also heat the device.)
After a specified time elapses (i.e., one hour), the device will have cooled to
ambient temperature and its measured resistance will revert to ten ohms
maximum (or likely less).
73--
Brad? AA1IP
