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2006-01-04 by stephan2148
Hi, Does anyone know if the RTC on the LPC2148 will still hold date/time if it has a separate lithium battery and crystal and the micro has lost power? I was hoping to powerdown totally and still have the RTC active. If not, I will have to use the sleep and idle modes. Thanks!
2006-01-04 by Dan Beadle
Yes, that is my understanding. I have a board just coming up on second pass. Memory is retained. Currents are extremely low. Using the RTC wakeup feature (set for a second or so hence), you can have a very, very low system budget. In my system, I expect to have batteries last 6+ months. First pass boards confirm this number. AMAZING for an ARM. _____
From: lpc2000@yahoogroups.com [mailto:lpc2000@yahoogroups.com] On Behalf Of stephan2148 Sent: Wednesday, January 04, 2006 8:25 AM To: lpc2000@yahoogroups.com Subject: [lpc2000] LPC2148 RTC/PowerDown Hi, Does anyone know if the RTC on the LPC2148 will still hold date/time if it has a separate lithium battery and crystal and the micro has lost power? I was hoping to powerdown totally and still have the RTC active. If not, I will have to use the sleep and idle modes. Thanks! _____ YAHOO! GROUPS LINKS * Visit your group "lpc2000 <http://groups.yahoo.com/group/lpc2000> " on the web. * To unsubscribe from this group, send an email to: lpc2000-unsubscribe@yahoogroups.com <mailto:lpc2000-unsubscribe@yahoogroups.com?subject=Unsubscribe> * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> . _____ [Non-text portions of this message have been removed]
2006-01-04 by Tom Walsh
stephan2148 wrote: >Hi, >Does anyone know if the RTC on the LPC2148 will still hold date/time >if it has a separate lithium battery and crystal and the micro has >lost power? I was hoping to powerdown totally and still have the RTC >active. > > I'm doing this with the LPC2138. You have to design the battery ciruit using two diodes and a resistor. The diodes will switch the RTC supply over to battery / main supply. The resistor limits current to the battery when the main power is up and will trickle charge (top off) the battery. Contact me directly if you want the circuit. TomW -- Tom Walsh - WN3L - Embedded Systems Consultant http://openhardware.net, http://cyberiansoftware.com "Windows? No thanks, I have work to do..." ----------------------------------------------------