Re: [volt-nuts] Fall of SRAM voltage in a 3457A without external power
On Mon, Jan 25, 2016 at 11:46:19AM +, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: > V). and well above the 2.0 V needed to hold the SRAM contents. Assuming the > SRAM takes a constant current one would expect the voltage to fall linearly > with time. If so, it would take 46 minutes to fall to 2.0 V even without > battery power. Hello David. I think you can probably assume the SRAM idle current be proportional to e(k*v) (an experimental k for some microcontrollers with SRAM I used was 0.44), so it should decay even more slowly. Best regards, Andrea Baldoni ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] Fall of SRAM voltage in a 3457A without external power
I decided to try a little experiment on my 3457A, When on mains the SRAM gets 4.8 ~ 5 V. This does not seem to be well regulated, so I assume depends on mains voltage. Once power is removed, the voltage on the SRAM stays well above the battery voltage for some considerable time, which I assume is due to a decoupling capacitor. My 10 M Ohm input Z multimeter is loading the circuit too much to continuously monitor the voltage, but a few checks indicated the voltage across the SRAM is falling quite slowly. Starting at 4.8 V from mains power, after 23 minutes of no mains power, the voltage on the SRAM was at 3.4V, which is above the battery voltage (3.03 V). and well above the 2.0 V needed to hold the SRAM contents. Assuming the SRAM takes a constant current one would expect the voltage to fall linearly with time. If so, it would take 46 minutes to fall to 2.0 V even without battery power. ESD and leakage of the human body would probably make screw this up, so I'm not suggesting replacing the battery that way if you want to preserve the contents of the SRAM, but there's a fairly good chance the contents would remain in RAM if one was reasonably quick, especially if you topped the voltage up from the mains just before removing it from the chassis. Dr. David Kirkby Ph.D CEng MIET Kirkby Microwave Ltd Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK. Registered in England and Wales, company number 08914892. http://www.kirkbymicrowave.co.uk/ Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please) ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Fall of SRAM voltage in a 3457A without external power
In message, "Dr. David Kirkby (Kirkby Microwave Ltd)" writes: >ESD and leakage of the human body would probably make screw this up, so I'm >not suggesting replacing the battery that way if you want to preserve the >contents of the SRAM, but there's a fairly good chance the contents would >remain in RAM if one was reasonably quick, especially if you topped the >voltage up from the mains just before removing it from the chassis. I usually hook up a separate battery while doing such surgery. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Fall of SRAM voltage in a 3457A without external power
On 25 January 2016 at 11:50, Poul-Henning Kampwrote: > > In message < > canx10hcamahhhxqiao9bdzu03c2bbt787mr10rmnywk3oa8...@mail.gmail.com> > , "Dr. David Kirkby (Kirkby Microwave Ltd)" writes: > > >ESD and leakage of the human body would probably make screw this up, so > I'm > >not suggesting replacing the battery that way if you want to preserve the > >contents of the SRAM, but there's a fairly good chance the contents would > >remain in RAM if one was reasonably quick, especially if you topped the > >voltage up from the mains just before removing it from the chassis. > > I usually hook up a separate battery while doing such surgery. > Yes, it is the logical thing to do, but there's a reasonable chance one could get away with it, but obviously if its important to keep the data, one would use an external supply. I'm tempted to purposely let the data become corrupted for the reasons I gave in another thread. Dave ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.