I am testing RTC(Real Time Clock) on Mistral REV G board with AM3715 processor. The backup battery on Power board has around 2.5V. I change the system time and power cycle the unit. I expect to see that backup battery should keep the new time but it doesn't. I know RTC works since I test it with wakeme application and it works as expected. I found something interesting in the document as the following:
188.8.131.52.3 Backup Events
Table 5-13 lists the events that put the device in BACKUP state.
Table 5-13. Backup EventsBackup Event Mode State TransitionMain battery < VMBLO (= 2.7 V typ). M, S BACKUP → ONTo stay in BACKUP state, mainbattery and backup battery > VBNPR(= 1.8 V typ).
Does that mean the condition to transit state to BACKUP is (main battery < 2.7V && (main battery and backup battert > 1.8V ))?
My understanding is that backup battery should provide power for the backup domain registers and 32KHz clock. But it seems not that way.
Can anyone explain how the backup battery works with TPS659xx module?
P.S. We have a different product which has an external rtc chip and a backup battery. The real time is kept if I power cycle the device since the backup battery provides power for rtc domain registers and circuitry.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.