LPC2388 RTC with external crystal

[mohammadfaizan]

Hi, 

I was observing the behavior of RTC from several days, first I run the clock by power supply for 72 hours and the time variation is negligible. When I run the RTC on 3 volt battery (VBat), I am getting a difference of 3 sec, of every (24 hours), RTC time is leading by 3 seconds. I want to fix this error of 3 sec, is their a best way instead of using a calibration method. Please suggest

thanks & regards

Mohammad Faizan

[jamesbone]

Hello Mohamad,

The LPC2388 has two erratas related to the power supply of VBAT,  as you can see in the following document

https://www.nxp.com/docs/en/errata/ES_LPC2378_88.pdf 

This is way it is afecting the RTC with a huge leakege in the VBAT pin. 

Have a great day,
TIC

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[mohammadfaizan]

Thanks Jamesbone,

I think their is no room to make changes in hardware,  only I have to manage it through a software. Today I observe that 3 sec error occur when Date changes, so I try reset or shift the time 3 second,

            if(RTC_HOUR >= 23)
                  {
                     if(RTC_MIN >=59)
                        {
                          if(RTC_SEC == 59)
                                {
                                  RTC_SEC = 56;
                                }

                       }

                 }

But I got stuck here, executing same statement again and again. can you suggest a smart way to calibrate the RTC clock time.