The answer is the normal power source is an unregulated 10v that feeds a
switching DC-DC converter
to generate 5v for other components, and a 3v regulator for the MSP.
The DC-DC converter itself draws more power than the MSP itself,
but in shutdown mode it draws essentially no power.
Thomas W. Carley wrote:
My question to you is: Why are you using a capacitor to power the msp430?
Why not just us the normal power source? If you are trying to turn off
something else, can you just shut off power AFTER the msp430?
-----Original Message-----
From: mspgcc-users-ad...@lists.sourceforge.net
[mailto:mspgcc-users-ad...@lists.sourceforge.net] On Behalf Of Kelly Murray
Sent: Tuesday, May 04, 2004 12:55 PM
To: mspgcc-users@lists.sourceforge.net
Subject: [Mspgcc-users] sleep mode power consumption
Hello,
I've got a system where I use the MSP430 to turn off the power if the
system is
idle for some time, and then wake it back up if there is any user input.
Of course, this is not possible, if the power is off, the MSP430 can't run!
But I use a .22F 3v capacitor that is charged up while power is on, and
then runs
the MSP when the power is off.
The strange thing is that when I monitor the
voltage after power-down, the cap is loosing voltage rather quickly,
about .01 v per second,
until it hits 1.66V and then stays there. This should be less than the
voltage needed to run the MSP?
I think the specs say 1.8v. However, it does still seem to be running,
because it is still monitoring
the input and turns the power back on.
My guess is that perhaps this behavior is "just lucky", that at 1.66v
the MSP is barely operating.
Alternatively, I suspect that because the 1.66v is also used as a logic
pin to shutdown the power,
it may be dipping below an "off" value for a tiny fraction of time,
just enough to give the cap
some juice enough to run the MSP, but not detectable by my voltmeter.
Anyone have any ideas or suggestions? Isn't 1.66v too low to operate
the MSP4301232 ?
Any why is cap dropping so quickly from 3v, in shutdown mode, it should
draw very little power,
just enough to wake up every second and do a A/D reading.
thanks for any input,
Kelly Murray
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