Monitor supply voltage of chip?


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  1. #1


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    Default Re: Monitor supply voltage of chip?

    microchip has a to92 voltage detector...... different voltages and draws 1 microamp....
    http://ww1.microchip.com/downloads/e...Doc/21434g.pdf

  2. #2
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    Default Re: Monitor supply voltage of chip?

    @robbo78
    That solution is not good for battery.
    With zener regulator current draw from battery is same in if pic is sleep mode as in run mode.
    If you use zener, then feed that voltage into analog pin, and then do ADC. This way current thru zener can be few uA instead few mA.

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    Default Re: Monitor supply voltage of chip?

    I don't know how wedded you are to the PIC12F683 but PIC12f617 looks similar but with a 0.6v ref but no EEPROM (although it can self write so that needn't be a show stopper).

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    Default Re: Monitor supply voltage of chip?

    PIC 12F1822 has FVRs and eveyrthing else you need.

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    Default Re: Monitor supply voltage of chip?

    I recently made a low battery warning for a 12V lead acid battery using a 12F675. B+ 12V powers the PIC through a 3.3V LDO regulator.The same B+ 12V goes to the ADC pin through a 220K resistor. The ADC pin then has 47K to ground. Here's the code I used. It flashes an LED when the battery gets weak. Perhaps you can tweak the code and circuit for your application to put the PIC in low power mode.

    ANSEL = 0 'all inputs digital ADC command will convert it to analog
    CMCON = 7 'comparators off
    DEFINE OSCCAL_1K 1 ' Set OSCCAL for 1K device
    TRISIO = %00000001 'INPUT ANA0 FOR ADC READINGS
    GPIO = 0 'ALL OUTPUTS LOW
    BATTEST VAR BYTE
    @ DEVICE MCLR_OFF, WDT_ON, BOD_ON, PWRT_ON, PROTECT_ON

    TEST:
    Clear 'CLEAR BATTEST
    ADCIN 0,BATTEST 'TEST CHARGE
    IF BATTEST <= 166 Then GoSub BLINK
    GoTo TEST

    BLINK:
    High GPIO.2
    Pause 500
    Low GPIO.2
    Pause 500
    Return

  6. #6


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    Default Re: Monitor supply voltage of chip?

    PIC 12F1822 has FVRs and eveyrthing else you need.
    Oh yes, thats nice. I don't understand why I didn't find that in the truly horrible Microchip selector... but of course, it's terrible.

  7. #7
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    Default Re: Monitor supply voltage of chip?

    @ pedja,

    sheesh, your right, I'm not sure which datasheet I was looking at but it wasn't for the 12f683.

    As others have pointed out there are other choices such as the 12f1822, etc. that do.
    Dwight
    These PIC's are like intricate puzzles just waiting for one to discover their secrets and MASTER their capabilities.

  8. #8
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    Default Re: Monitor supply voltage of chip?

    @robbo78
    That solution is not good for battery.
    With zener regulator current draw from battery is same in if pic is sleep mode as in run mode.
    If you use zener, then feed that voltage into analog pin, and then do ADC. This way current thru zener can be few uA instead few mA.
    Good idea! I have just found this part which is a bit of a "cheat", and quite cheap? - http://www.farnell.com/datasheets/1669371.pdf

    EDIT: Just realised that "amgen" already stated this

    microchip has a to92 voltage detector...... different voltages and draws 1 microamp....
    http://ww1.microchip.com/downloads/e...Doc/21434g.pdf
    Last edited by robbo78; - 26th February 2016 at 19:06.

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