terahz
1x10^12 Hz
Oops, that sux. Sorry.
However, 141F is fine, given that the thermal shutdown is at 320F.
I've had 7 XPGs running at 18mA (lowest DAC setting) for about 1hr now. Vin is 25V, Vfw is 18.37V. Once I put my pinky on the IC, I don't feel any heat for the fist 4 seconds, then 3 seconds later it is too hot to hold. I used my computer's fan controller to measure about 120F, but I don't know how accurate that is given the tiny chip and the clunky probes the controller has.
If I turn Vin up to 26V, the chip becomes considerable hotter. Going to Vin 24, takes about 15 seconds of touch to become really hot, but I wouldn't call it too hot to hold.
At 22Vin the chip is barely over ambient temperature.
So, If switching frequency can be correlated to temperature, it looks like this:
400kHz - slightly above ambient.
450kHz - gets to "too hot to touch" after about 7-10 seconds (110F is probably a good measure of where 'too hot to touch' starts)
500kHz - too hot to touch in about 3 seconds.
That would support what you guys are observing as well.
Still, I wouldn't be worried about it at 150F. It might be worth tweaking Roff and Coff to get a lower frequency for some people.
If you are worried about the heat, add a second Coff(C5) on top of the current one (in parallel) and I'm sure that will make a big difference.
Don't forget to report back guys.
However, 141F is fine, given that the thermal shutdown is at 320F.
I've had 7 XPGs running at 18mA (lowest DAC setting) for about 1hr now. Vin is 25V, Vfw is 18.37V. Once I put my pinky on the IC, I don't feel any heat for the fist 4 seconds, then 3 seconds later it is too hot to hold. I used my computer's fan controller to measure about 120F, but I don't know how accurate that is given the tiny chip and the clunky probes the controller has.
If I turn Vin up to 26V, the chip becomes considerable hotter. Going to Vin 24, takes about 15 seconds of touch to become really hot, but I wouldn't call it too hot to hold.
At 22Vin the chip is barely over ambient temperature.
So, If switching frequency can be correlated to temperature, it looks like this:
400kHz - slightly above ambient.
450kHz - gets to "too hot to touch" after about 7-10 seconds (110F is probably a good measure of where 'too hot to touch' starts)
500kHz - too hot to touch in about 3 seconds.
That would support what you guys are observing as well.
Still, I wouldn't be worried about it at 150F. It might be worth tweaking Roff and Coff to get a lower frequency for some people.
If you are worried about the heat, add a second Coff(C5) on top of the current one (in parallel) and I'm sure that will make a big difference.
Don't forget to report back guys.