Monitor supply voltage of chip?

[LinkMTech]

I think a fixed Vdd to the PIC set below the "low battery" level is your only recourse with this one.
Then a simple voltage divider to monitor the battery level with the A/D to trigger sleep mode after that.

If you're not sourcing much through the 12F1683, a small 2.?V zener is all you'll need for Vdd.

[Heckler]

The datasheet for the 12f683 shows that it has an internal Fixed Voltage Reference that can be used to compare against the supply voltage.

[Acetronics2]

The datasheet for the 12f683 shows that it has an internal Fixed Voltage Reference that can be used to compare against the supply voltage.

hi, Dwight,

not really a reference for the 683 ...

- Programmable on-chip voltage reference
(CVREF) module (% of VDD)

so, here it is not possible to reach the goal ...

Alain

[pedja089]

There is more than one way to to this. All you need is fixed reference voltage.
Eg 0,6V from diode(if you can tolerate drift about 2mV/degC), some pic have built in diode for temp. monitoring, or pic fixed reference(FVR), or voltage from some blinking LED(Do battery check when LED is on).
So you can feed fixed voltage on ADC pin, and use Vdd as reference for ADC. If Vdd is lower than ADC result are higher and reverse.
Some pic have FVR on ADC multiplexer(or internal diode), so there is convenient way to do that, without loosing io pins.
If you are using external fixed reference, you can use IO pin to turn on/off reference to minimize current draw.

[Heckler]

Hey Robbo,

If you decide to use the internal Fixed Voltage Reference you might want to take a look at my second post in this tread... http://www.picbasic.co.uk/forum/showthread.php?t=19035

and read this thread also... http://www.picbasic.co.uk/forum/showthread.php?t=17321

sorry that my post about the FVR earlier was so short but I was at work.

[towlerg]

have a look at AN1072. Darrel wrote a piece about the subject.

[pedja089]

Heckler
According to microchip's datasheet( http://ww1.microchip.com/downloads/e...oc/41211D_.pdf ) PIC12F683 doesn't have Fixed Voltage Reference.