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Why is my processor consuming more power than its datasheet suggests?

beatgammit 7y ago
We had a similar issue, but with date corruption instead of just excess power usage. Always tie every input to something, don't just leave them unused.
flyinglizard 7y ago
Reminds me of the development of a battery powered medical device I did about 7 years ago. We selected an esoteric Freescale microcontroller for that project (which was successfully used in such applications before), but for the life of me I couldn't get the power consumption in deep sleep to come anywhere near the spec (few microamps IIRC). Eventually, after scanning the datasheet forward and backward again and again, I had this idea which turned out to be the right answer: microcontrollers usually come in several package configurations, each with a different number of pins. Freescale used the same silicon die in all of the variants of that microcontroller, and left unrouted pins floating internally. I had to write to registers which, on paper, didn't even exist on this processor variant to put all I/Os in a defined state. The power consumption then came within the spec.
kazinator 7y ago
TL;DR: if you don't treat unused pins according to the datasheet recommendations, then all bets are off. This is even true with lowly things like op-amps. If you have a dual op-amp IC, and you use only one op-amp, you should do something appropriate with the pins of the unused one. http://www.ti.com/lit/an/sboa204a/sboa204a.pdf http://www.ti.com/lit/an/sboa204a/sboa204a.pdf
cr0sh 7y ago
Better question - where did they get a datasheet? Ok - I haven't read the article - maybe they're talking about some processor where the manufacturer actually provides a datasheet. Most companies do. I think even AMD does; I know you can get datasheets for the ARM implementations, and most other embedded processors... ...but has anyone found any recent Intel processor datasheets (ok, maybe at this point they'd be several volume databook libraries - but you know what I mean)? The last time I tried to find something recent from Intel, the most recent datasheet of any kind I could find (one that listed technical stuff like registers, pins, opcodes, etc - not just some basic figures and marketing junk), I think the latest I found was for the Core2 Duo/Quad series - then nothing after that? Is there some secret trick to getting these? All I could figure at the time was that you had to be part of some program or something, maybe with an NDA - or an actual motherboard manufacturer or something? But then again, how would you write a compiler without the information about opcodes and such? Now honestly - I don't need such datasheets. But I wanted to look at something "cutting edge" or relatively new (and really, the Core2 datasheet was good enough for this) - and compare it with old datasheets for like the 6809 or 6502 or Z-80, old-school 8-bit processors (the ones I grew up with) - just to see how things have changed (or haven't) and how "insane" things have gotten. More like a lark for a laugh kind of thing that anything else. It just struck me that I couldn't easily find them for recent Intel stuff...at least, not easily on the web (but again, maybe I wasn't looking in the right area, or there are other reasons at play).
- anonymfus 7y ago
  > Ok - I haven't read the article - maybe they're talking about some processor where the manufacturer actually provides a datasheet. You don't ever need to read the article, URI is enough to know the manufacturer. > The last time I tried to find something recent from Intel, the most recent datasheet of any kind I could find (one that listed technical stuff like registers, pins, opcodes, etc - not just some basic figures and marketing junk), I think the latest I found was for the Core2 Duo/Quad series - then nothing after that That was the last generation supported by non-Intel chipsets. It is not a coincidence.
- fmntf 7y ago
  > Is there some secret trick to getting these? All I could figure at the time was that you had to be part of some program or something, maybe with an NDA - or an actual motherboard manufacturer or something? Yes, hardware manufacturers have access to a ton of (well written) "intel confidential" pdf files.
- pjc50 7y ago
  The article is from Analog. They link the datasheet (or at least a datasheet) at the bottom. He's a FAE for Analog. He can, if necessary, find the people who wrote the datasheet and drop by their desk.
- segfaultbuserr 7y ago
  "Processor" here refers to something like your ATMega2560 (or in this article, ARM Cortex-A5 MCU), not Intel or AMD desktop processors. It should have been named "microcontroller", but I used the original title per guidelines. The bottomline is, at least skim through the article to make sure your comment is on-topic.
persistent 7y ago
The Analog Dialog is a treasury of good advice going back decades. Really worth your time if you have any interest at all in electronics.
deleted 7y ago
[deleted]

We had a similar issue, but with date corruption instead of just excess power usage. Always tie every input to something, don't just leave them unused.

flyinglizard 7y ago

Reminds me of the development of a battery powered medical device I did about 7 years ago. We selected an esoteric Freescale microcontroller for that project (which was successfully used in such applications before), but for the life of me I couldn't get the power consumption in deep sleep to come anywhere near the spec (few microamps IIRC). Eventually, after scanning the datasheet forward and backward again and again, I had this idea which turned out to be the right answer: microcontrollers usually come in several package configurations, each with a different number of pins. Freescale used the same silicon die in all of the variants of that microcontroller, and left unrouted pins floating internally. I had to write to registers which, on paper, didn't even exist on this processor variant to put all I/Os in a defined state. The power consumption then came within the spec.

kazinator 7y ago

TL;DR: if you don't treat unused pins according to the datasheet recommendations, then all bets are off. This is even true with lowly things like op-amps. If you have a dual op-amp IC, and you use only one op-amp, you should do something appropriate with the pins of the unused one. http://www.ti.com/lit/an/sboa204a/sboa204a.pdf http://www.ti.com/lit/an/sboa204a/sboa204a.pdf

cr0sh 7y ago

Better question - where did they get a datasheet? Ok - I haven't read the article - maybe they're talking about some processor where the manufacturer actually provides a datasheet. Most companies do. I think even AMD does; I know you can get datasheets for the ARM implementations, and most other embedded processors... ...but has anyone found any recent Intel processor datasheets (ok, maybe at this point they'd be several volume databook libraries - but you know what I mean)? The last time I tried to find something recent from Intel, the most recent datasheet of any kind I could find (one that listed technical stuff like registers, pins, opcodes, etc - not just some basic figures and marketing junk), I think the latest I found was for the Core2 Duo/Quad series - then nothing after that? Is there some secret trick to getting these? All I could figure at the time was that you had to be part of some program or something, maybe with an NDA - or an actual motherboard manufacturer or something? But then again, how would you write a compiler without the information about opcodes and such? Now honestly - I don't need such datasheets. But I wanted to look at something "cutting edge" or relatively new (and really, the Core2 datasheet was good enough for this) - and compare it with old datasheets for like the 6809 or 6502 or Z-80, old-school 8-bit processors (the ones I grew up with) - just to see how things have changed (or haven't) and how "insane" things have gotten. More like a lark for a laugh kind of thing that anything else. It just struck me that I couldn't easily find them for recent Intel stuff...at least, not easily on the web (but again, maybe I wasn't looking in the right area, or there are other reasons at play).

anonymfus 7y ago
> Ok - I haven't read the article - maybe they're talking about some processor where the manufacturer actually provides a datasheet. You don't ever need to read the article, URI is enough to know the manufacturer. > The last time I tried to find something recent from Intel, the most recent datasheet of any kind I could find (one that listed technical stuff like registers, pins, opcodes, etc - not just some basic figures and marketing junk), I think the latest I found was for the Core2 Duo/Quad series - then nothing after that That was the last generation supported by non-Intel chipsets. It is not a coincidence.
fmntf 7y ago
> Is there some secret trick to getting these? All I could figure at the time was that you had to be part of some program or something, maybe with an NDA - or an actual motherboard manufacturer or something? Yes, hardware manufacturers have access to a ton of (well written) "intel confidential" pdf files.
pjc50 7y ago
The article is from Analog. They link the datasheet (or at least a datasheet) at the bottom. He's a FAE for Analog. He can, if necessary, find the people who wrote the datasheet and drop by their desk.
segfaultbuserr 7y ago
"Processor" here refers to something like your ATMega2560 (or in this article, ARM Cortex-A5 MCU), not Intel or AMD desktop processors. It should have been named "microcontroller", but I used the original title per guidelines. The bottomline is, at least skim through the article to make sure your comment is on-topic.

persistent 7y ago

The Analog Dialog is a treasury of good advice going back decades. Really worth your time if you have any interest at all in electronics.

deleted 7y ago

[deleted]