Go Down

Topic: crystals for atmel chips (Read 3470 times) previous topic - next topic

retrolefty

i see minor reduction in chip current and lower unloaded voltage.  you really need specialized probe to view that with a scope.  

the real difference is sensitivity to external noise and pcb layout which can be a big problem.  one infamous case was the m1284 fiasco where many believed defective ic but really was bad user design practices.  switching to full swing pretty much solved the problems.  i saw similar issues with at90s parts back in the old days.  low power mode is what i consider to be one of the poor choices made by team arduino.


artists... cant live with em... cant shoot em...  well you could but then we would have nothing to gripe about. :)

 I agree. The standard Arduino board (UNO) would never be a candidate for low power operation as the board has on-board continuous loads that swap any meaningful savings from the AVR chip. 


jboyton

#46
Sep 21, 2015, 07:12 pm Last Edit: Sep 21, 2015, 07:15 pm by jboyton
the real difference is sensitivity to external noise and pcb layout which can be a big problem.  one infamous case was the m1284 fiasco where many believed defective ic but really was bad user design practices.  switching to full swing pretty much solved the problems.
I hadn't heard about that issue. Those were interesting threads to read.

I measured about 1.4mA difference between full swing and low power fuse settings with a 328p at 5V. That sure isn't enough to worry about on a typical Arduino board. Elsewhere maybe.


Code: [Select]
Atmega328p, 8MHz crystal, 5V, 25°C, error in parts per million

none 22pf 18pf current, mA
----- ---- ---- -----------
+235 -14 +9 - low power,  fast rise (lfuse:0xFF) 9.7
+235 -14 +9 - low power,  slow rise (lfuse:0xEF) 9.7
+251 -25 -3 - full swing, fast rise (lfuse:0xF7) 11.1
+251 -25 -3 - full swing, slow rise (lfuse:0xE7) 11.1

john1993

well that is some useful data.  even led power takes bigger hits.  really gives an overview hard to ferret out of spec sheets.  funny how a thread started on noobie confusion can produce info worthy of saving to hd.

Go Up