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Hot!Current in Reset vs Complete Shutdown (PIC16F)

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acharnley
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2020/08/13 05:14:07 (permalink)
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Current in Reset vs Complete Shutdown (PIC16F)

I'm using a PIC16F as a glue chip and I have two options to shut it down, either hold it in reset, or send a command over to shut-down everything and go to sleep.
 
The reset is simpler to implement but I can't find a figure to indicate how much current is consumed in this mode (I guess the SPI used for programming uses the SPI CLK so the main CPU isn't necessarily running - but I could be wrong).
#1

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    1and0
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/13 05:43:07 (permalink)
    +3 (3)
    acharnley
    The reset is simpler to implement but I can't find a figure to indicate how much current is consumed in this mode...

    With a current meter?.!
    #2
    acharnley
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/13 07:03:05 (permalink)
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    Yeah that's the hard way - my prototype board isn't geared up for it.
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    NKurzman
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/13 07:44:00 (permalink)
    +2 (2)
    Get a cheap eval board or a Proto board.
    Put the chip on it hold it and reset and measure the current.

    You could put a support ticket into Microchip to ask them if they have information on this.
    But I doubt they do.
    #4
    upand_at_them
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/13 11:43:22 (permalink)
    +1 (1)
    acharnleyYeah that's the hard way - my prototype board isn't geared up for it.

     
    You can't measure current into your board??
    #5
    acharnley
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/13 13:11:12 (permalink)
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    upand_at_them
    acharnleyYeah that's the hard way - my prototype board isn't geared up for it.

     
    You can't measure current into your board??



    No, I have a lot more stuff then the PIC on it so no accuracy.
    #6
    ric
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/13 13:43:52 (permalink)
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    acharnley
    I'm using a PIC16F as a glue chip and I have two options to shut it down, either hold it in reset, or send a command over to shut-down everything and go to sleep.
    ...

    You do realise that in reset mode, all the pins will revert to input mode with no pullups?
    Your PCB would have to ensure that EVERY pin was pulled to a valid level to ensure low power consumption.
    That's much simpler to arrange if you don't reset the PIC, but implement a low power mode.
     
     

    I also post at: PicForum
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    #7
    dan1138
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/13 13:49:20 (permalink)
    +1 (1)
    For most PIC16F controllers the lowest power state is not always when MCLR is asserted.
     
    This is because that GPIO pins become inputs when MCLR is asseted but those that do not have analog function become digital inputs. The GPIO pin digital input buffers may oscillate when the input voltage floats to switching threshold.
     
    To get most PIC16F controllers to the lowest possible power state:
    1 - Disable the watchdog timeout and brown out resets
    2 - Mask all interrupt sources
    3 - Clear the GIE bit in the INTCON register
    4 - Set analog GPIO pins for analog mode and inputs
    5 - Set digital GIPO output pins to high or low that draws the lowest system power
    6 - Execute the SLEEP opcode
     
    From this state the controller requires an MCLR or power cycle to restart.
     
    When you get it all right the PIC will draw less than 2 microamps and typically less than 300 nanoamps.
     
    These current levels are notoriously difficult to measure accurately even with the proper instrumentation.
    post edited by dan1138 - 2020/08/13 13:55:25
    #8
    acharnley
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/13 14:50:52 (permalink)
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    All the pins are utilised, none can float or oscillate. I'll go with SLEEP (what Dan said).
    #9
    ric
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/13 15:18:41 (permalink)
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    acharnley
    All the pins are utilised, none can float or oscillate.

    So none are outputs just connected to a high impedance input on another device?
     

    I also post at: PicForum
    Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
    NEW USERS: Posting images, links and code - workaround for restrictions.
    To get a useful answer, always state which PIC you are using!
    #10
    acharnley
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/14 00:31:43 (permalink)
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    ric
    acharnley
    All the pins are utilised, none can float or oscillate.

    So none are outputs just connected to a high impedance input on another device?



    Nope, everything has a pull up/down or a chip which internally has one.


    #11
    ric
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    Re: Current in Reset vs Complete Shutdown (PIC16F) 2020/08/14 01:01:59 (permalink)
    0 (2)
    acharnley
    Nope, everything has a pull up/down or a chip which internally has one.

    That's relevant information that should have been in the original question...

    I also post at: PicForum
    Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
    NEW USERS: Posting images, links and code - workaround for restrictions.
    To get a useful answer, always state which PIC you are using!
    #12
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