Timeline for How to implement a soft power switch controllable by microcontroller?
Current License: CC BY-SA 2.5
7 events
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| May 30, 2011 at 1:45 | comment | added | supercat | A bigger issue that switch bounce is processor behavior during power-down. In particular, it may be good to make sure that the processor can only turn the supply on when its VDD is above the point where correct operation is guaranteed. I've had to tweak some auto-power-down circuits that would occasionally fail as a consequence of the processor running random code when VDD fell below the valid operating voltage. The random code could set the "power on" output high, which would in turn power the device back up, running code at a random address. | |
| Jan 14, 2011 at 17:03 | comment | added | Kortuk | I have seen some crazy bounce on switches before. | |
| Jan 14, 2011 at 16:36 | comment | added | tcrosley | @Kortuk, good point. I was assuming the micro would turn on fast enough that it could override the switch before the first bounce, assuming driving the pin high was the first thing the micro did. If that isn't the case, one could add a capacitor on the -SHDN lead to create a time constant for the turn on (although this would also introduce a slight delay in turn off). The 10 nF one probably needs to be left in for noise suppression (it was included in a datasheet sample schematic). Or one could add additional RC circuit for just the switch. | |
| Jan 14, 2011 at 15:39 | comment | added | Kortuk | Very important, I would think, is debouncing that switch. | |
| Jan 14, 2011 at 14:07 | history | edited | tcrosley | CC BY-SA 2.5 |
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| Jan 14, 2011 at 12:28 | vote | accept | cksa361 | ||
| Jan 14, 2011 at 11:59 | history | answered | tcrosley | CC BY-SA 2.5 |