Thanks Jan,
? That is a good way of looking at it. I just wonder why it takes
hours/days at room temp too come back down to/towards 1.5 ohms.
That said, my circuit will likely never see that fuse trip anyway,
I am just adding it to cover me as it will be a device that plugs
into a USB port and only controls LED's. I am pretty sure USB hubs
and pc motherboards also use ptc fuses to protect the motherboard.
Dave
On 11/9/2019 12:52 AM, Jan Kok wrote:
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I would treat the PTC as a very loose-tolerance
resistor. Make sure your circuit will work properly if the PTC
resistance is anywhere between 1.5 and 10 ohms. It's probably
close to 10 ohms soon after tripping or being soldered, and may
drift back down toward 1.5 ohms after hours or days at room
temperature.
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.
Question: If I were to figure in the resistance for the PTC
fuse as part
of my equation for selecting the correct resitors further down
the
circuit...What number in ohms should I use? In other words,
when the
circuit is in normal operation, what will the resistance of
the PTC
actually be?
Thanks,
Dave
