Go Down

Topic: Board powering via Analog pins? (Read 60 times) previous topic - next topic

Davey-Jones

Hi All,

Just a quick question: Should the board power-up if a power source is applied across A0 and GND?

I've been working on a datalogging project that monitors the voltage values of a few Lithium Polymer cells over their life span. I noticed that my board gets powered when i connect my battery sense leads to the analog inputs.

It does make sense & obviously the solution is to place a large resistance in series with the AI's but its strange that ive not seen this mentioned at all anywhere :smiley-surprise:

CrossRoads

Power can leak thru the clamp to VCC and clamp to Gnd pin protection diodes make the chip appear to be partially powered. If current going in that way exceeds 1A, the diode and other pin parts can be damaged.
That's why the spec says Vin High not to exceed VCC + 0.5V, and Vin Low not to go below Gnd - 0.5V.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

DrAzzy

1A? That doesn't sound right...
ATtiny core for 841+1634+828  http://goo.gl/6fRf8e
ATtiny core for x4/x5/x61/x7/x8 series http://goo.gl/O5Wtyu
ATtiny 841/1634/828/88/861/167 breakouts, mosfets, touch sensors and prototyping board in my store http://goo.gl/xyUN2v

Go Up