Why wouldn't you connect the output of the voltage monitor (MAX809, FM809, TCM809, etc.) to the *RESET line of the MSP430? When the power drops below the monitor level (say 2.9 V for a 3.3V system) the *RESET is held low until power returns.
Are you seeing this in ALL flavors of MSP, or just older (2.7 -5.5V) parts? Thanks, John Gilbert --------------------------------------------------------------------------- > From: Matthias Weingart <[email protected]> > To: [email protected] > Date: Tue, 8 Oct 2002 18:40:43 +0200 > Subject: Reset was Re: [Mspgcc-users] Guys, what do you think of this... > Reply-To: [email protected] > > On Tue, Oct 08, 2002 at 08:57:50AM +1000, Harry Lemmens wrote: > > > Another problem I have seen with the MSP430 is difficulty with Reset. I > > (now) deliberately load the MSP supply rail with a 1K resistor to drop the > > supply rail on powerdown, as otherwise it takes several seconds for the > > supply to drop enough to guarantee that a correct reset occurs. (A 2u2 > > capacitor takes a long time to discharge through the powering down current > > of just the MSP, probably nano-amps below 1 volt...) The Data sheet spec for > > reset to be guaranteed is 0.4 to 0.0 volts, the supply can easily hover in > > this region for many seconds without some extra load. > > Reset and brown out protection is a real problem with the MSP430. > Your 1k resistor solution is far away from a "low power" design ;-(. I have > no real working solution yet, but a voltage monitor could help to tie the > supply of the MSP430 low, if the input voltage is low. Unfortunately that > monitor chips only have one switching element. E.g. Zetex ZXCM209R is > switching to ground in a reset condition (open collector). > > A good solution could be to connect the power supply of the MSP430 to > the output of a special reset circuit - that circuit should have a > high side switch and a low side switch. > The high side switch is on if the voltage is ok. The MSP gets the power > through the highside switch. It is off and the low side switch is on > at power failure to bring the voltage at the MSP430 down very fast. > I think there is no ready made chip for this and I have not yet a good > an reliable discrete solution. It is difficult to keep it working below 1 > volt, > pn and zener voltages are temperature dependent, zeners need current ... > Maybe a combination of a voltage monitor chip and some external components > could be the solution, but hey I am ending now with 90% of my components on > the pcb used for the reset circuit ;-(. > > Matthias > > > ------------------------------------------------------- > This sf.net email is sponsored by:ThinkGeek > Welcome to geek heaven. > http://thinkgeek.com/sf > _______________________________________________ > Mspgcc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/mspgcc-users >
