AN401 - Charging Methods for the F-RAM RTC Backup Capacitor

AN401 describes the charging methods for the F-RAM RTC (FM31xxx/FM33xxx Processor Companion family) backup capacitor. A backup capacitor is used for backing up the real-time clock and event counters.

Introduction

The F-RAM real-time clock (RTC), which includes the FM31xxx/FM33xxx Processor Companion family devices, provide an option to backup RTC and event counters in the absence of system power through a backup power source (V_BAK). V_BAK can be either a battery or a capacitor. However, often a capacitor is preferred.