MAX756 - sudden drop on voltage from 3.3V to 1.7V a

[ecerulm]

Related to this other thread viewtopic.php?f=8&t=10490&p=49488&e=49488

I just set up the MAX756 by using the example circuit in the datasheet (http://datasheets.maxim-ic.com/en/ds/MAX756-MAX757.pdf). I mounted it on a breadboard and I get 3.3V with no load and a sound 3.3V when I connect simple load (3 led + 3 resistors). But when I connect the vout to the arduino pro mini vcc pin it doesn´t work. I get 3.3V for 5 or 6 seconds, the arduino seems to work, the red led is on and the green led blinks (I have loaded a sketch that toggles green led on and off). But after 5 seconds, the vout voltage drops to 1.7 (1 second maybe) and then it goes back to 3.3V. The arduino red led (power) goes to half bright during this low voltage phase and it resets when voltage goes up again. Then it stays perfectly stable at 3.3V and after 5 seconds the same thing repeats. There are a number of other stuff connected to the arduino and breadboard (ds1620, hmc6352, MMA7260Q, TEMT6000).


I guess that the answer could be the same as in the other thread (viewtopic.php?f=8&t=10490&p=49488&e=49488). problems with the ground connection. It seems that switched mode power supply (SMPS) are really much more harder to use by the hobbyist than LDO voltage regulators. At least they're harder to use than I thought.

I think I will revert to using two coin cells and power the whole thing using the arduino step down voltage regulator instead. It wont be as efficient as using the MAX756 but probably is easier to get it working

[Zener]

Just as a guess, it sounds like thermal shutdown behavior. I wouldn't think that your load is much, but you might put your finger on it when it does that and see if it is hot. Yes, switchers are a whole other animal, and I wouldn't put them on a breadboard. You could probably get away with a soldered perfboard but even that could have issues. You can get an eval board from Maxim.

[ecerulm]

I was thinking about buying a MintyBoost and simply cut a trace to change the 5V to 3V output.

[Zener]

The SP6648 is a nice part and you can sample a EVB SP6648EB

http://www.exar.com/Common/Content/Prod ... ParentID=2