topic Re: backup battery for rtc in lpc1227 in LPC Microcontrollers

backup battery for rtc in lpc1227

lpcware — Wed, 15 Jun 2016 17:02:52 GMT

Content originally posted in LPCWare by dariush_abbasi868 on Sun Nov 30 21:52:52 MST 2014
hello every body.

Has lpc1227 3.3v battery for rtc ?
if main power removed what happen for rtc actually?

Re: backup battery for rtc in lpc1227

lpcware — Wed, 15 Jun 2016 17:02:53 GMT

Content originally posted in LPCWare by dariush_abbasi868 on Tue Dec 02 03:21:10 MST 2014
did you use of rtc in lpc1227?
of course you have this problem in your hardware designing !
or maybe I am in wrong doing .
please reply to me.

Re: backup battery for rtc in lpc1227

lpcware — Wed, 15 Jun 2016 17:02:54 GMT

Content originally posted in LPCWare by NXP_Paul on Tue Dec 02 06:59:32 MST 2014
The RTC in the LPC122x family is powered by VDD(3V3). If the power to this pin is removed, the RTC is no longer functional.

- Paul

Re: backup battery for rtc in lpc1227

lpcware — Wed, 15 Jun 2016 17:02:54 GMT

Content originally posted in LPCWare by dariush_abbasi868 on Tue Dec 02 21:39:51 MST 2014
thank you
you means that we don't need any backup rtc power and we have to power lpc12Xx always ?

i think it is awful , isn't it?

Re: backup battery for rtc in lpc1227

lpcware — Wed, 15 Jun 2016 17:02:55 GMT

Content originally posted in LPCWare by fjrg76 on Fri Apr 17 16:10:01 MST 2015
Yep, that's awkward. When the term "RTC" is read one thinks it's a real "real time clock", but it's not. Maybe you are looking for a "RTC with independent power domain". Some chips include that option, but others don't.

The RTC in the LPC1227 is just a periodic interrupt, with no other capabilities (alarms, day of time, etc.). Perhaps it's too late, but there are cheap and nice chip-off RTCs, like MCP9700, that costs under a dollar.

Another turn-around is that you power the chip with two voltage sources, the main one as usual, and other from a backup battery that powers the chip whenever the main supply has gone. At hardware level only a couple of shottky diodes are needed, whilst in software you must turn the chip off (entering to the lowest power saving profile) so it doesnt' drain the backup battery.