Re: [AVR-Chat] Brownout - will this idea work?
2006-01-20 by MuRaT KaRaDeNiZ
altough the BOD peripheral is available in almost every member of avr family, the peripheral directly resets the micro. There can be cases where you want to do some action , in the last 100ms cpu time just before the supply fails, for example, save some volatile variables to eeprom. What i suggest is: You can use comparator to compare a resistive scaled version to one of the internal voltage references, thereby get rid of regular polling of the adc channel, and you will respond to the event almost instantaneously. digitally filtering the comparator output is also fast and easy. And a note: Sensing the input side of the linear regulator supplying the micro will give more time regards Murat karadeniz Http://www.onlinefavbar.com/mukas/
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-----Original Message-----
From: "Thomas Keller" <tkeller1@neb.rr.com>
Sent: 14.01.06 18:40:48
To: "AVR-Chat@yahoogroups.com" <AVR-Chat@yahoogroups.com>
Subject: Re: [AVR-Chat] Brownout - will this idea work?
Ted Smith wrote:
| Is it possible to use the ADC input to sense the supply voltage and
| automatically drive a spare output connected across the reset pin to
>zero when the supply sank to say 4 volts and thus act as a brownout
>detector?
>If you had a diode to a big enough capacitor for the microcontroller
>supply, the voltage would only fade slowly and I would think you would
>only need to poll the adc every half second or so.
>You might have to enable this only after the ADC was initialised and
>stable after startup.
>
>
My only question is why bother with all this? Is there an AVR device
that doesn't include the integrasted BOD periphersl? I haven't looked
st the data sheets for every AVR there is, but to the best of my
recollection, every one I have looked at inclkuded BOD on chip.
tom
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