Product Overview
The PCF8563T/5,518 from NXP is a low-power CMOS real-time clock/calendar with I2C interface and only 0.25 µA backup current. It provides century, year, month, day, weekday, hour, minute, second counting with alarm and timer functions.
Key Specifications
| Function | CMOS real-time clock / calendar |
| Interface | I2C (up to 400 kHz) |
| Clock Output | Programmable 32.768 kHz to 1 Hz |
| Supply Voltage | 1.0V to 5.5V |
| Backup Current | 0.25 µA at 3.0V |
| Alarm | Minute/hour/day/weekday alarm |
| Package | SOIC-8 (3.9×4.9mm) |
Working Principle
A 32.768 kHz crystal drives the timebase. Divider chain counts seconds through centuries. I2C interface reads/writes all time registers. A dedicated VDD backup pin allows a coin cell to maintain timekeeping when main power is removed, consuming only 0.25 µA. Programmable CLKOUT provides system clock or low-frequency tick.
Applications
- Embedded system RTC
- Power management timer
- Event timestamping
- Alarm/wake-up scheduling