20 posts and still no schematic. Looks like the OP doesn't want a real answer..That sounds like it is loaded down more than 800 mA.
ak
20 posts and still no schematic. Looks like the OP doesn't want a real answer..That sounds like it is loaded down more than 800 mA.
Cut him a bit of slack, he is either an early riser ( posted at 5am) or he lives on the other side of the big blue marble.20 posts and still no schematic. Looks like the OP doesn't want a real answer..
ak
125 deg where? On the heat sink or on the die itself? What counts?Your regulator is probably fine.
From the Fairchild datasheet:
" Each type employs internal current limiting, thermal shut-down, and safe operating area protection."
This means that if your 7805 is still regulating, it is not too hot.
The maximum operating temperature is 125°C, water boils at 100°C, and it is unlikely you can hold your hand in boiling water for long at all
It's the junction temperature that counts. At a dissipation of 5W, the temperature differential between case and junction is 25C.125 deg where? On the heat sink or on the die itself? What counts?
The original poster mentioned that the output had dropped a bit to 4.90 V. Initially I took that as excessive current. Could it be over temp kicking in?It's the junction temperature that counts. At a dissipation of 5W, the temperature differential between case and junction is 25C.
The regulator has thermal protection, so it should be able to protect itself from over temperature.
Could normal operation, 4.8-5.2V according to the datasheet, or any combination of over temp, dropout/ripple, oscillation, ... After a couple dozen posts, we still don't have a schematic...The original poster mentioned that the output had dropped a bit to 4.90 V. Initially I took that as excessive current. Could it be over temp kicking in?
Obviously the chip only knows its own temperature so its the die temperature that counts.125 deg where? On the heat sink or on the die itself? What counts?