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joseph20480
Joined: 21 Dec 2011 Posts: 42
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Pic24fj16ga004 PLL and consumption |
Posted: Wed Apr 20, 2022 6:01 am |
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dear every one,
I have some difficulty with my pic and the pll.
At 8Mhz (no pll) > Consumption OK
At 32Mhz, my consumption is more 30mA !!!
My pic : pic24fj64ga004
Frequency Clock : 32Mhz with PLL.
Code: |
#fuses FRC_PLL,NOWDT,NOPROTECT,NODEBUG,NOJTAG
#use delay(clock=32M)
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Code: |
void main (void)
{
for(;;){}
}
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please tell me if you see something wrong, i'm little confuse ... |
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newguy
Joined: 24 Jun 2004 Posts: 1903
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Posted: Wed Apr 20, 2022 6:46 am |
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You have to ensure that all unused peripherals are turned off. Your current consumption will fall as you find and kill these overlooked current draws. |
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Ttelmah
Joined: 11 Mar 2010 Posts: 19369
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Posted: Wed Apr 20, 2022 7:21 am |
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Agreed, you are probably making it worse with all the stuff floating,
But that is a price you pay for speed. The data sheet tells you that the
core current of the chip can be up to about 20mA at 32MHz, only about
a quarter of that at 8MHz. TANSTAAFL in performance terms...
Turning off the unused stuff and making sure the pins are not floating, should
save perhaps 30%, but it is going to draw more as you go faster.
You are making the consumption slightly worse with your clock setup. Change
to:
Code: |
#include <24FJ16GA004.h>
#fuses NOWDT,NOPROTECT,NODEBUG,NOJTAG
#use delay(INTERNAL=32M)
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By default your current setup will be enabling the oscillator output, which
means a pin running fast, and drawing quite a noticeable extra current. |
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temtronic
Joined: 01 Jul 2010 Posts: 9174 Location: Greensville,Ontario
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Posted: Wed Apr 20, 2022 7:29 am |
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One of those 'speed kills' things.
Static CMOS consumes very,very little power,with proper pullups.
Active CMOS consumes power ,based upon speed and/or 'transactions' (0/1/0/1/...).
Going from 8MHz to 32MHz is X4, so I'd expect X4+- increase in current. it's a simple 'math' thing.
Now you're also using the PLL, so additional power is needed to run that.
It's just the 'nature of the beast'....
Since you're concerned about power, I assume you're battery powered ?
Now there are 'tricks', some already mentioned. Another is 'waking up, run fast, then sleep'. How fast depends on what needs to be done. Or you can vary the speed. |
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joseph20480
Joined: 21 Dec 2011 Posts: 42
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Posted: Wed Apr 20, 2022 9:24 am |
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temtronic wrote: | One of those 'speed kills' things.
Static CMOS consumes very,very little power,with proper pullups.
Active CMOS consumes power ,based upon speed and/or 'transactions' (0/1/0/1/...).
Going from 8MHz to 32MHz is X4, so I'd expect X4+- increase in current. it's a simple 'math' thing.
Now you're also using the PLL, so additional power is needed to run that.
It's just the 'nature of the beast'....
Since you're concerned about power, I assume you're battery powered ?
Now there are 'tricks', some already mentioned. Another is 'waking up, run fast, then sleep'. How fast depends on what needs to be done. Or you can vary the speed. |
Thanks for all reply !
So nothings to do... bad luck... :-) |
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Ttelmah
Joined: 11 Mar 2010 Posts: 19369
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Posted: Wed Apr 20, 2022 10:46 am |
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Yes, and no, you should be able to reduce it quite a bit by making sure you
have no pins floating, and turning off the peripherals you don't want. The
data sheet figure at 32MHz is about 20mA. |
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