Operating voltages

hippy

Technical Support
Staff member
The "PICAXE Manual 1" gives a list of operating voltages for various PICAXE's along with a number of caveats ...

PICAXE-08 PIC12F629-I/P 2.0V
PICAXE-08M PIC12F683-I/P 2.0V
PICAXE-18 PIC16F627 (A)-04/P 3.0V (2.0V)
PICAXE-18A PIC16F819-I/P 2.0V
PICAXE-18X PIC16F88-I/P 2.0V
PICAXE-28A PIC16F872-I/SP 3.0V
PICAXE-28X PIC16F873A-I/SP 2.0V
PICAXE-40X PIC16F874A-I/P 2.0V

As some ( all ? ) of the minimum voltages are only applicable to PICAXE's operating at below 4MHz, which by default the PICAXE's don't, would it not make sense to state what the actual operating voltage ranges are for each PICAXE at particular operating frequencies ?

Also, some of the minimum voltages claimed differ to what the datasheets for the PICmicro's I have say, and are totally unachievable. For example, the 18X ( 16F88 ) shows 2.0V minimum in the PICAXE manual, but the datasheet shows that as being for the 16<b>LF </b> 88 only, the 16<b>F </b> 88 is shown as 4.0V to 5.5V.

I'll be the first to admit that Microchip's datasheets are not the easiest to unravel in the area of operating voltage, but some clarification with respect to the PICAXE would help ... some poor student struggling aginst the impossible to get an 18X working properly on 2 x 1.5V batteries when the manual says it can will perhaps one day appreciate it ;-)
 

hippy

Technical Support
Staff member
Having gone through the datasheets I have to hand, which may be superseded so E&amp;OE, the manufacturer's stated operating voltages I can determine from the Frequency-Voltage graphs, and associated electrical characteristics data tables for 4MHz, 8MHz and16MHz operation are ...

PICAXE-08 PIC12F629-I/P 2.0V-5.5V
PICAXE-08M PIC12F683-I/P 2.0V-5.5V
PICAXE-18 PIC16F627 (A)-04/P 3.0V-5.5V (3.0V-5.5V)
PICAXE-18A PIC16F819-I/P 4.0V-5.5V
PICAXE-18X PIC16F88-I/P 4.0V-5.5V
PICAXE-28A PIC16F872-I/SP 4.0V-5.5V
PICAXE-28X PIC16F873A-I/SP 4.0V-5.5V
PICAXE-40X PIC16F874A-I/P 4.0V-5.5V

Is the reality then that the PICAXE is guaranteed to work at the above voltages, and may work below them, but it's luck of the draw ?

Edited by - hippy on 7/22/2004 4:25:05 AM
 

BeanieBots

Moderator
It also depends on if the brownout bit has been set. I've not scrutinised the data sheets to know for sure but I can confirm that I have many 18Xs and 28Xs which have proved reliable running on 2 X NiCd (2.2v Nom.) Whilst they have all continued to work at 2.0v, programming becomes erratic below 2.1v. This could of course only be applicable to the particular batch that I have.
 

hippy

Technical Support
Staff member
According the Rev-Ed data, brownout is turned on on the 08/08M ( about 2.2V ) but turned off on the rest ( about 4.2V ) - your experience seems to confirm that, my 08 testing stopped working at 2.2V.
 
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