Definition: A Real Time Clock (RTC) is a low-power hardware clock circuit that keeps track of time even when the main system power is off.

Key Features:

• Runs on battery or backup power (e.g., CR2032)
• Maintains year, month, day, hour, minute, second
• Often includes calendar functions (leap year, daylight saving)
• Communicates via I2C, SPI, or parallel interface

Common ICs:

• DS1307 – I2C, simple, widely used
• DS3231 – High accuracy, integrated temperature-compensated crystal
• PCF8563 – Low power, I2C
• RV-3028 – Ultra-low power, high accuracy

Applications:

• Embedded systems
• Data loggers
• Industrial controllers
• Consumer electronics

Design Tips:

• Use a dedicated 32.768 kHz crystal if not integrated
• Ensure clean power and proper decoupling
• Include battery backup path with diode or power-fail circuit
• Consider temperature range and aging for long-term accuracy