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AN404 - F-RAM RTC BACKUP SUPPLY (VBAK PIN) AND UL COMPLIANCE | Cypress Semiconductor

AN404 - F-RAM RTC BACKUP SUPPLY (VBAK PIN) AND UL COMPLIANCE

Last Updated: 
Aug 18, 2017
Version: 
*C

AN404 discusses the F-RAM RTC processor companion’s backup power sources, the internal charging circuit, and the associated issues.

Overview

The FM31xx and FM33xx families are the Integrated Processor Companion devices that feature a real-time clock (RTC). The RTC provides the date/time information for the system and operates on either VDD or VBAK power. A battery or a capacitor is attached to the VBAK backup power-supply pin. This application note discusses the backup power sources, the internal charging circuit, and the associated issues.