Other Parts Discussed in Thread: STRIKE
In an application board (in production for many years now) we use the ADS7846 for touch-panel control and RTC battery monitor.
Now on a board installed in field and working well for more than one year, suddenly RTC was reported not backed-up.
The cause was investigated and initially found in battery discharged; later on VBAT pin of touch-controller was found to have very low impedance to ground, and this was supposed to be primary failure for battery discharging and RTC failure. Nevertheless the rest of the controller - and namely the touch-panel control function - continued to work perfectly.
We changed ADS7846 (and battery, of course) and everything then returned fine. This confirmed that problem was touch-controller failure.
How is it possible a VBAT pin failure? Consider that in the installation plant the board and the battery were not directly accessible for anybody, nor battery was replaced or accessed or touched.
