Power Consumption on PIC12F675

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Billoo
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Power Consumption on PIC12F675

Post by Billoo »

Hi Everyone,

I have just discovered something very odd and maybe someone could enlighten me to what could be happening?

Some may know that I have had some issues with trying to get the little PIC sleep current down close to specs for my LED project, as the 0.260mA at 3V was just to much, and also rising to 0.640mA at 5V! Initially I had about 5 chips sourced from Maplin as it was local (bought at different times over 3 months), and I have had the issue with all of them.

I have been trying many of the suggestions, different pull downs, sinking high and low and different code etc. but with no joy.

Today I took delivery of some more PIC12F675's but this time from Farnell and I just flashed one with the exact same code with the exact same Pickit3 and used it on the exact same breadboard, but this time the chip is shutting down and the drain is so low I cant even register it on my bench meter on micro amps.

Out of interest, I tried a few more, still good, went back to the orginals, still bad. Any ideas?

Cheers
Bill

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Re: Power Consumption on PIC12F675

Post by Benj »

Hi Bill,

As your programming with the PICkit, you can see the revision of the various chips.

For example.
Connecting to MPLAB PICkit 3...

Currently loaded firmware on PICkit 3
Firmware Suite Version.....01.50.04
Firmware type..............PIC18F

Programmer to target power is enabled - VDD = 5.000000 volts.
Target device PIC18F4585 found.
Device ID Revision = 7
It might be worth looking at the microchip page for the device, scroll to the bottom of the page and expand the documentation section and there should be an Errata document that details all the various changes between revisions.

http://ww1.microchip.com/downloads/en/D ... 80125H.pdf

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Re: Power Consumption on PIC12F675

Post by Billoo »

Benj wrote:Hi Bill,

As your programming with the PICkit, you can see the revision of the various chips.

For example.
Connecting to MPLAB PICkit 3...

Currently loaded firmware on PICkit 3
Firmware Suite Version.....01.50.04
Firmware type..............PIC18F

Programmer to target power is enabled - VDD = 5.000000 volts.
Target device PIC18F4585 found.
Device ID Revision = 7
It might be worth looking at the microchip page for the device, scroll to the bottom of the page and expand the documentation section and there should be an Errata document that details all the various changes between revisions.

http://ww1.microchip.com/downloads/en/D ... 80125H.pdf
Many thanks Benj, I will check this out :D

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Re: Power Consumption on PIC12F675

Post by QMESAR »

Billoo wrote: Out of interest, I tried a few more, still good, went back to the orginals, still bad. Any ideas?
You originals is most likely not original Microchips but some china made chip with Microchip details printed on it :D We had that issue a few times
when a PIC does not run on its spec take the pint numbers on it and ask Microchip to track the manufacturing batch ,and 100% of time they inform you that it is not a Microchip batch number be careful where you by any mcu's not only PIc there many Chinese clowns floating on the market
Farnell,Mousers and Digikey are some people you can be sure it is a PIC and not a Chinese PIC :D :D

In 15 years I never saw a real PIC not running on spec or at least have the issue documented in the Errata with a fix.

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Re: Power Consumption on PIC12F675

Post by faveremario »

Hi Billoo, Hi all

I just finished some hobby-tests on a 18F4455 (lots of pins) on high-current-consumption when the PIC is went to sleep. Mine consumed over 40µA after the sleep-command. Not really good according to the specs that µchip is giving us.

First of all consider all things you already did : taking care of floating inputs.
* The long-term impact of floating inputs for all ports is about 2µA (depending on the environment).
* However, the desktop Fluke45 learned me a lot about the time-lapse to get the current down to 2µA. It took 10+ seconds for the current to fall-back to 2µAmps. During this lapse the battery is drained. So for energy consumption's sake, it is a huge harvesting if you can get the current to drop as fast as possible.

Second thing : do not underestimate the consumption of hardware components.
* It is quite useful to consider disabling all things you don't need, but that are enabled by default. And that is not only for the A/D module that flowcode enables by default. Take a look on the generated C-program & check the data-sheets.
* I found out, for example, that the Brown-out detector is standard enabled, but consumes a HUGE amount of current: 39µA !!! Disabling it in the configuration panel makes the consumption in sleep-mode dropping from 39µA to quasi 0.000mA. Unfortunately I did not have the financial possibility to buy a more convenient desktop-meter. So there was ending my quest for better battery-life... unless KeySight wants a place of honour in my book giving me their entry-level DMM ;) ... not? Oh well I tried.


Hope it helped...
Greetz.

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Re: Power Consumption on PIC12F675

Post by Steve001 »

Hi

You can measure the current with a muiltimeter but It all depends what accuracy are you looking for? Some muiltermeters have uA range but the burden voltage of the meter is high this affects the accuracy of your reading. You can solve this easily using an external circuit. All you need is a resistor and an precision opamp.

Dave Jones from the EEVBlog designed this circuit that lets you use your muiltimeter in DC Volts mode to measure precisely nA, uA and mA with good resolution. You can find the schematic and pcbs designs files in

http://www.eevblog.com/projects/ucurrent/

Hope this helps

Steve
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Re: Power Consumption on PIC12F675

Post by Docara »

faveremario wrote:
However, the desktop Fluke45 learned me a lot about the time-lapse to get the current down to 2µA.
On no it didnt. The Fluke45 did not "learned" you a lot" the Fluke34 taught you a lot

Just saying ...... :wink:

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Re: Power Consumption on PIC12F675

Post by faveremario »

Ah yes... My Italian is not so good anymore. :lol:

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Re: Power Consumption on PIC12F675

Post by faveremario »

Datasheets are always wright :P

OK i'm just proud to show-off my brand new Rigol DMM :lol:
I know EEV would be a good deal... but hell, we don't live to work, but work to live!
I also know this thing will teach me a lot of things :wink:
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