Timeline for 3.3V @ 10mA from 5V - 35V
Current License: CC BY-SA 2.5
11 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Nov 12, 2010 at 18:53 | vote | accept | Thomas O | ||
| Nov 12, 2010 at 3:29 | comment | added | Kortuk | Do not use a zener. They will not give you regulated voltage like you get with a wonderful linear regulator and they will kill power. | |
| Nov 10, 2010 at 17:36 | comment | added | Kortuk | @thomas, telling me that the 35V could be continuous is something I did not account for. I would have given the same answer though. I have used in excess of 30V with a small surface mount package and more than 10mA. I give a nice big ground plane. | |
| Nov 10, 2010 at 17:27 | comment | added | Mark | something like a linear.com/pc/productDetail.jsp?navId=H0,C1,C1040,P86928 in a DFN package with the thermal pad tied to the ground plane with 3-4 vias would work fine. Based on the data sheet you would need something like 25cm^2 of copper to allow operation up to ~90C ambient. Which if you have a ground plane in the board and the board is bigger than 5cm x 5cm should be fine. If you can do a ground pour on the surface layer around the IC, even better. | |
| Nov 10, 2010 at 17:10 | comment | added | Thomas O | It's also not a worst case scenario, a lot of people will be using 30V battery packs with this. | |
| Nov 10, 2010 at 17:07 | comment | added | Thomas O | Yeah, but I can't spare space for through hole. It's also a waste of space in that the micro is in a tiny SO20 package but the reg is in a TO-220... How would zener diodes work? they have higher dissipation ratings, maybe it would work better? | |
| Nov 10, 2010 at 17:04 | comment | added | Kortuk | 350mW absolutely worse case is not that bad. that is if you are at 38V in. If you get a good ground plane to conduct heat, or use through hole with a heat sink(which I can put watts into without a problem) you can handle this. The question of heat dissipation we have had other places. This will easily be handled with small surface-mount linear regulator(I have done this much power that way). | |
| Nov 10, 2010 at 16:51 | comment | added | Thomas O | 350mW is a lot for small surface mount components. | |
| Nov 10, 2010 at 16:50 | comment | added | Mark | efficiency gain from a buck regulator at only 10mA would be questionable as well, especially at the 35V point, the duty cycle would be really low. | |
| Nov 10, 2010 at 16:32 | history | edited | Kortuk | CC BY-SA 2.5 |
added a tiny bit more.
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| Nov 10, 2010 at 16:22 | history | answered | Kortuk | CC BY-SA 2.5 |