I've just read the archives and it appears that the power on reset circuit in the MSP430F149 is useless for brownout detection, even with the watchdog enabled? What I'm seeing is that unless I put a load on the 3.3v regulator to make sure it drops to 0v the msp430 doesn't reset properly. I expected that in the case where power dropped, but didn't go below 0.4, and came back up that the watchdog circuit would then reset the part and all would be good. But it appears that if power is glitched (and we all know that's going to happen eventually) the processor gets into a non-working state without even the watchdog running. Seems kinda dumb to me. Unless I'm missing something here. Thanks for any comments or suggestions, Brian -- ----------------- Brian C. Lane (W7BCL) Programmer www.shinemicro.com RF, DSP & Microcontroller Design
Power on Reset
Started by ●July 15, 2003
Reply by ●July 15, 20032003-07-15
I am not 100% sure but the behavior I've seen is perfectly compatible with your statements. -----Mensaje original----- De: Brian C. Lane [mailto:brian@bria...] Enviado el: Martes, 15 de Julio de 2003 07:13 p.m. Para: msp430@msp4... Asunto: [msp430] Power on Reset I've just read the archives and it appears that the power on reset circuit in the MSP430F149 is useless for brownout detection, even with the watchdog enabled? What I'm seeing is that unless I put a load on the 3.3v regulator to make sure it drops to 0v the msp430 doesn't reset properly. I expected that in the case where power dropped, but didn't go below 0.4, and came back up that the watchdog circuit would then reset the part and all would be good. But it appears that if power is glitched (and we all know that's going to happen eventually) the processor gets into a non-working state without even the watchdog running. Seems kinda dumb to me. Unless I'm missing something here. Thanks for any comments or suggestions, Brian -- ----------------- Brian C. Lane (W7BCL) Programmer www.shinemicro.com RF, DSP & Microcontroller Design . ">http://docs.yahoo.com/info/terms/
Reply by ●July 15, 20032003-07-15
It is totally dumb, this one got by Ti. Newer parts solve the problem.
(Don'y they always) but aren't released yet. The 15x and `16x family
seminars are just being advertised now. Of course those of us not in
America or Canada will get to wait an extra few months, and probably
won't get the same deal on an EVK.
Al
Brian C. Lane wrote:
> I've just read the archives and it appears that the power on reset
> circuit in the MSP430F149 is useless for brownout detection, even with
> the watchdog enabled?
>
> What I'm seeing is that unless I put a load on the 3.3v regulator to
> make sure it drops to 0v the msp430 doesn't reset properly. I expected
> that in the case where power dropped, but didn't go below 0.4, and
came
> back up that the watchdog circuit would then reset the part and all
> would be good.
>
> But it appears that if power is glitched (and we all know that's going
> to happen eventually) the processor gets into a non-working state
> without even the watchdog running.
>
> Seems kinda dumb to me. Unless I'm missing something here.
>
> Thanks for any comments or suggestions,
>
> Brian
>
Reply by ●July 15, 20032003-07-15
Well they aren't really claiming to be a brownout reset circuit are
they?
It's a POR circuit.
If your power supply goes to as high as full voltage and down to <0.4V
reliably every time, you don't need a brownout circuit. Otherwise you need
to add a brownout circuit.
----- Original Message -----
From: "Brian C. Lane" <brian@bria...>
To: <msp430@msp4...>
Sent: Wednesday, July 16, 2003 8:13 AM
Subject: [msp430] Power on Reset
> I've just read the archives and it appears
that the power on reset
> circuit in the MSP430F149 is useless for brownout detection, even with
> the watchdog enabled?
>
> What I'm seeing is that unless I put a load on the 3.3v regulator to
> make sure it drops to 0v the msp430 doesn't reset properly. I expected
> that in the case where power dropped, but didn't go below 0.4, and
came
> back up that the watchdog circuit would then reset the part and all
> would be good.
>
> But it appears that if power is glitched (and we all know that's going
> to happen eventually) the processor gets into a non-working state
> without even the watchdog running.
>
> Seems kinda dumb to me. Unless I'm missing something here.
>
> Thanks for any comments or suggestions,
>
> Brian
>
> --
> -----------------
> Brian C. Lane (W7BCL) Programmer
> www.shinemicro.com RF, DSP & Microcontroller Design
>
>
>
>
> .
>
>
>
> ">http://docs.yahoo.com/info/terms/
>
>
>
Reply by ●July 15, 20032003-07-15
David Lions wrote: > Well they aren't really claiming to be a brownout reset circuit are they? > It's a POR circuit. > > If your power supply goes to as high as full voltage and down to <0.4V > reliably every time, you don't need a brownout circuit. Otherwise you need > to add a brownout circuit. You will find that the recommended decoupling caps for the micro will hold battery supplies at around 0.8V. Al > > ----- Original Message ----- > From: "Brian C. Lane" <brian@bria...> > To: <msp430@msp4...> > Sent: Wednesday, July 16, 2003 8:13 AM > Subject: [msp430] Power on Reset > > > >>I've just read the archives and it appears that the power on reset >>circuit in the MSP430F149 is useless for brownout detection, even with >>the watchdog enabled? >> >>What I'm seeing is that unless I put a load on the 3.3v regulator to >>make sure it drops to 0v the msp430 doesn't reset properly. I expected >>that in the case where power dropped, but didn't go below 0.4, and came >>back up that the watchdog circuit would then reset the part and all >>would be good. >> >>But it appears that if power is glitched (and we all know that's going >>to happen eventually) the processor gets into a non-working state >>without even the watchdog running. >> >>Seems kinda dumb to me. Unless I'm missing something here. >> >>Thanks for any comments or suggestions, >> >>Brian >> >>-- >>----------------- >>Brian C. Lane (W7BCL) Programmer >>www.shinemicro.com RF, DSP & Microcontroller Design >> >> >> >> >>. >> >> >> >>">http://docs.yahoo.com/info/terms/ >> >> >> > > > > > . > > > > ">http://docs.yahoo.com/info/terms/ > > >
Reply by ●July 16, 20032003-07-16
This sounds pretty scary, and is likely enough to warrent being taken into consideration during design... What do you folks use to correct this? I ran into this with some older PICs, and used one of the MN1380 series "Power Monitors" to cure it. Panasonic makes them, Digikey has some. Unfortunately, reviewing the specs shows they can draw as much as the MSP430 during sleep mode :( 1 uA typical, 5 uA max... Here's a link for data: http://downloads.solarbotics.net/pdf/mn1380.pdf Here's one to Digikeys catalog on them (also shows Microchips versions): http://dkc3.digikey.com/PDF/T032/0482.pdf -----Original Message----- David Lions wrote: > Well they aren't really claiming to be a brownout reset circuit are they? > It's a POR circuit. > > If your power supply goes to as high as full voltage and down to <0.4V > reliably every time, you don't need a brownout circuit. Otherwise you need > to add a brownout circuit. You will find that the recommended decoupling caps for the micro will hold battery supplies at around 0.8V. Al --------------------------------- Do you Yahoo!? SBC Yahoo! DSL - Now only $29.95 per month!
Reply by ●July 16, 20032003-07-16
Brian, the POR circuit is indeed useless for brownout detection because
it's
a POR circuit not a brownout circuit.
If you bring the supply voltage down less than 0.4V then it shoudl reset, if
it doesn't you have found a bug.
If you bring the voltage to just above 0.4V, the POR won't work and if you
are below the minimum operating voltage of 0.8V, the watchdog might not work
either. This is because the watchdog is a digital counter, not a
voltage-based reset.
So if you bring it down near 0.4 but not under, it could indeed lock up.
This is why you need a brownout circuit, to guarantee a reset when the
voltage is out of spec.
----- Original Message -----
From: "Brian C. Lane" <brian@bria...>
To: <msp430@msp4...>
Sent: Wednesday, July 16, 2003 8:13 AM
Subject: [msp430] Power on Reset
> I've just read the archives and it appears
that the power on reset
> circuit in the MSP430F149 is useless for brownout detection, even with
> the watchdog enabled?
>
> What I'm seeing is that unless I put a load on the 3.3v regulator to
> make sure it drops to 0v the msp430 doesn't reset properly. I expected
> that in the case where power dropped, but didn't go below 0.4, and
came
> back up that the watchdog circuit would then reset the part and all
> would be good.
>
> But it appears that if power is glitched (and we all know that's going
> to happen eventually) the processor gets into a non-working state
> without even the watchdog running.
>
> Seems kinda dumb to me. Unless I'm missing something here.
>
> Thanks for any comments or suggestions,
>
> Brian
>
> --
> -----------------
> Brian C. Lane (W7BCL) Programmer
> www.shinemicro.com RF, DSP & Microcontroller Design
>
>
>
>
> .
>
>
>
> ">http://docs.yahoo.com/info/terms/
>
>
>
Reply by ●July 16, 20032003-07-16
So get a brownout circuit. Maybe they can't or don't want to get the POR threshold up to 0.8V? I disagree that it's 'totally dumb' or that one 'got by' them. The datasheet does say "POR" doesn't it? It does operate according to the parameters given within the datasheet doesn't it? I could not find any references to 'brownout reset'. I don't think they are claiming that the POR should work as a brownout reset. So really, it's not dumb, nothing got by them and it works exactly the way they specified it, am I right? I think whats really happening here is that someone a) didn't read the question b) didn't read the datasheet, or c) doesn't know the difference between brownout and POR :p David. -*Public defender of huge, faceless multinationals*- ----- Original Message ----- From: "onestone" <onestone@ones...> To: <msp430@msp4...> Sent: Wednesday, July 16, 2003 12:05 PM Subject: Re: [msp430] Power on Reset > David Lions wrote: > > Well they aren't really claiming to be a brownout reset circuit are they? > > It's a POR circuit. > > > > If your power supply goes to as high as full voltage and down to <0.4V > > reliably every time, you don't need a brownout circuit. Otherwise you need > > to add a brownout circuit. > > You will find that the recommended decoupling caps for the micro will > hold battery supplies at around 0.8V. > > Al > > > > > ----- Original Message ----- > > From: "Brian C. Lane" <brian@bria...> > > To: <msp430@msp4...> > > Sent: Wednesday, July 16, 2003 8:13 AM > > Subject: [msp430] Power on Reset > > > > > > > >>I've just read the archives and it appears that the power on reset > >>circuit in the MSP430F149 is useless for brownout detection, even with > >>the watchdog enabled? > >> > >>What I'm seeing is that unless I put a load on the 3.3v regulator to > >>make sure it drops to 0v the msp430 doesn't reset properly. I expected > >>that in the case where power dropped, but didn't go below 0.4, and came > >>back up that the watchdog circuit would then reset the part and all > >>would be good. > >> > >>But it appears that if power is glitched (and we all know that's going > >>to happen eventually) the processor gets into a non-working state > >>without even the watchdog running. > >> > >>Seems kinda dumb to me. Unless I'm missing something here. > >> > >>Thanks for any comments or suggestions, > >> > >>Brian > >> > >>-- > >>----------------- > >>Brian C. Lane (W7BCL) Programmer > >>www.shinemicro.com RF, DSP & Microcontroller Design > >> > >> > >> > >> > >>. > >> > >> > >> > >>">http://docs.yahoo.com/info/terms/ > >> > >> > >> > > > > > > > > > > . > > > > > > > > ">http://docs.yahoo.com/info/terms/ > > > > > > > > > > . > > > > ">http://docs.yahoo.com/info/terms/ > > >
Reply by ●July 16, 20032003-07-16
--- In msp430@msp4..., "Brian C. Lane" <brian@s...> wrote: > I've just read the archives and it appears that the power on reset > circuit in the MSP430F149 is useless for brownout detection, even with > the watchdog enabled? > > What I'm seeing is that unless I put a load on the 3.3v regulator to > make sure it drops to 0v the msp430 doesn't reset properly. I expected > that in the case where power dropped, but didn't go below 0.4, and came > back up that the watchdog circuit would then reset the part and all > would be good. > > But it appears that if power is glitched (and we all know that's going > to happen eventually) the processor gets into a non-working state > without even the watchdog running. > > Seems kinda dumb to me. Unless I'm missing something here. No, you don't miss anything. In a F148 design I used an LDO with an open-drain "power good" output connected to the MSP's reset pin to overcome this. Some of the MSPs DO have a brownout detector. It is OFF by default, you have to activate it. I used it in an F435 and it works very well. Wolfgang
Reply by ●July 16, 20032003-07-16
Or d) has an early data sheet before the POR threshhold was identified
as 0.4V.
Al
David Lions wrote:
> So get a brownout circuit. Maybe they can't or don't want to get
the POR
> threshold up to 0.8V?
>
> I disagree that it's 'totally dumb' or that one 'got
by' them.
>
> The datasheet does say "POR" doesn't it? It does operate
according to the
> parameters given within the datasheet doesn't it? I could not find
any
> references to 'brownout reset'. I don't think they are
claiming that the
> POR should work as a brownout reset.
>
> So really, it's not dumb, nothing got by them and it works exactly the
way
> they specified it, am I right?
>
> I think whats really happening here is that someone a) didn't read the
> question b) didn't read the datasheet, or c) doesn't know the
difference
> between brownout and POR
>
> :p
>
> David.
> -*Public defender of huge, faceless multinationals*-
>
> ----- Original Message -----
> From: "onestone" <onestone@ones...>
> To: <msp430@msp4...>
> Sent: Wednesday, July 16, 2003 12:05 PM
> Subject: Re: [msp430] Power on Reset
>
>
>
>>David Lions wrote:
>>
>>>Well they aren't really claiming to be a brownout reset circuit
are
>
> they?
>
>>>It's a POR circuit.
>>>
>>>If your power supply goes to as high as full voltage and down to
<0.4V
>>>reliably every time, you don't need a brownout circuit.
Otherwise you
>
> need
>
>>>to add a brownout circuit.
>>
>>You will find that the recommended decoupling caps for the micro will
>>hold battery supplies at around 0.8V.
>>
>>Al
>>
>>
>>>----- Original Message -----
>>>From: "Brian C. Lane" <brian@bria...>
>>>To: <msp430@msp4...>
>>>Sent: Wednesday, July 16, 2003 8:13 AM
>>>Subject: [msp430] Power on Reset
>>>
>>>
>>>
>>>
>>>>I've just read the archives and it appears that the power
on reset
>>>>circuit in the MSP430F149 is useless for brownout detection,
even with
>>>>the watchdog enabled?
>>>>
>>>>What I'm seeing is that unless I put a load on the 3.3v
regulator to
>>>>make sure it drops to 0v the msp430 doesn't reset properly.
I expected
>>>>that in the case where power dropped, but didn't go below
0.4, and came
>>>>back up that the watchdog circuit would then reset the part and
all
>>>>would be good.
>>>>
>>>>But it appears that if power is glitched (and we all know
that's going
>>>>to happen eventually) the processor gets into a non-working
state
>>>>without even the watchdog running.
>>>>
>>>>Seems kinda dumb to me. Unless I'm missing something here.
>>>>
>>>>Thanks for any comments or suggestions,
>>>>
>>>>Brian
>>>>
>>>>--
>>>>-----------------
>>>>Brian C. Lane (W7BCL) Programmer
>>>>www.shinemicro.com RF, DSP & Microcontroller Design
>>>>
>>>>
>>>>
>>>>
>>>>.
>>>>
>>>>
>>>>
>>>>">http://docs.yahoo.com/info/terms/
>
>>>>
>>>>
>>>
>>>
>>>
>>>.
>>>
>>>
>>>
>>>">http://docs.yahoo.com/info/terms/
>
>>>
>>>
>>
>>
>>.
>>
>>
>>
>>">http://docs.yahoo.com/info/terms/
>>
>>
>>
>
>
>
>
> .
>
>
>
> ">http://docs.yahoo.com/info/terms/
>
>
>
