The M41T66 is a low-power serial real-time clock (RTC) with a built-in 32.768 kHz oscillator (external crystal controlled). Eight registers are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. An additional 8 registers provide status/control of alarm, square wave, calibration, and watchdog functions. Addresses and data are transferred serially via a two line, bidirectional I2C interface. The built-in address register is incremented automatically after each WRITE or READ data byte.
Functions available to the user include a time-of-day clock/calendar, alarm interrupts, programmable square wave output, and watchdog output. The eight clock address locations contain the century, year, month, date, day, hour, minute, second and tenths/hundredths of a second in 24-hour BCD format. Corrections for 28-, 29- (leap year), 30- and 31-day months are made automatically.
The M41T66 is supplied in a 16-pin QFN.
- Counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century
- 32 KHz crystal oscillator integrating load capacitance and high crystal series resistance operation
- Oscillator stop detection monitors clock operation
- Serial interface supports I2 C bus (400 kHz)
- 525 nA timekeeping current at 3 V
- Low operating current of 35 μA (at 400 kHz)
- Timekeeping down to 1.0 V
- 1.3 V to 4.4 V I2
C bus operating voltage
- Allows use in lithium ion rechargeable applications
- 32 KHz square wave on power-up to drive a microcontroller in low-power mode
- Programmable (1 Hz to 32 KHz) square wave
- Programmable alarm with interrupt function
- Accurate programmable watchdog (from 62.5 ms to 31 min)
- Software clock calibration to compensate deviation of crystal due to temperature
- Automatic leap year compensation
- Operating temperature of –40 to 85 °C
- Lead-free 16-pin QFN package