Yes I realise when reading you post that since I will change the voltage through some gain I can do what i want whith it, the 5V value whas entairely hypothetical. But Is there generally any pros and cons to use a referens voltage very close to the rail compared to say in the middle between Vss and Vdd/GND?
Is there any advantage to go with a 3,3V supply instead of 5V?
I see more and more 3,3V supply chips(the ones i come in contact with is more ore less only for hobbyist intress and i don't know about the proffesional part of the electronics product world)
But is it any more than it's a lower voltage and we are moving more and more to lower levels in an power consumption struggle?
I guess i wonder if i have anything to gain from a change from my 5V based digital circuit to 3,3V? Fore uC, DAC and such.
First I thought "screw power consumption concerns" regarding low level controll circuits cous there are lots and lots of other more importent things to spend time on, but it feels sloppy and as learning for a future in the imdustry I will have a secondary priority to minimize power drawn by all circuits, and 3,3V seams like a good start.
Since it appears to basicly be the same thing whether i use 12-, 14- or 16-bit DAC, why not go for 16-bit so thats my plan, i think...
Since companys are so very kind to offer free sampels a good 16-bit DAC is a reality and boy do it boost my specs, not that I have any potential to become a big buyer but it sure creates costumer return.
Moving from 12-bit(4096) to 16-bit changes my approche(no spell check
) to the adjustment principle, I have never done anything like this and all i know is that i would like ta have a numpad to enter output values but am I on the right track with the following, the acctual value input manner is unrelavant but getting the controll voltage to a appropiate level:
the transformer makes 30V the aimed max voltage.
16-bit = 30V/65,536 = 457,7636719uV ~ 457,76uV
16-bit = 2,5V/65,536 * =*38,14697266uV ~ 38,14uV
500uV / 38,14uV = 13,109596622
38,14uV * 13,2Gain ~ 500mV
- - - Updated - - -
As for 0V,
The supply will be att PE-ground level but if I tell the supply to give me 10V I want a symetrical output, i start to remember that this begun as a battery supply
and i still aiming for att smal floating battery driven lab supply. But I need a real solid ~3A supply but when i have finished this transformer based circuit it will be a smal matter of make another version with lower current and a battery-bank.
In reality I'm crazed for a real tracking dual rail supply but in my current project path that will simply be a matter of software, no?
Both voltages will be continiusly monitored and displayed,
I also intend to fix a function to seperatly adjust the rails but that will have to wait untill Rev2, probobly. Theres really a need for me to open a new project thread and i have begun to write the post.
Edit//
I will need a ATmega2560,
http://www.atmel.com/Images/Atmel-2...r-ATmega640-1280-1281-2560-2561_datasheet.pdf
and it contains 16-bit PWM, but what determines accuracy and errors in the resulting final controll voltage?
Or to save you some time if you can anser this,
I don't neacecary need to understand what it depends on but whould a 16-bit DAC with performance (±0.5LSB INL and ±0.9LSB DNL) over tempera- ture without any adjustments. The DAC output is unbuffered, resulting in a low supply current of 0.3mA and a low offset error of 0.6mV be the better option.
Edit//
Iv'e found this,
http://www1.elfa.se/data1/wwwroot/assets/datasheets/ltAD420_e.pdf
Supply voltage 12-32V so with a good referens att 30V its all done with unitygain buffers, might that be a good idea?
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I can't say how much i appritiate all you help, i could not have gotten this far for a couple of months on my own. These are really new waters and man do I have a insain amount of datasheets read this week and theres more to come, datasheets that is.
Thanks a thousand.
This DAC/PWM have been a titanium nutt to ***** for me but i see the finishline very close and when the decision is made I can start to acctualy implement whatever software needed DAC/PWM wise.
Head ake is a side effekt of electronic project like this