The M41T6x is a low-power serial real-time clock (RTC) with a built-in 32.768 kHz oscillator. Eight registers are used for the clock/calendar function and are configured in binary-coded decimal (BCD) format. An additional eight registers provide status/control of alarm, 32 kHz output, 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 (M41T62/65), 32 kHz output (M41T62/64), programmable square wave output (M41T62/64), and watchdog output (M41T65). 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 M41T6x is supplied in two very small packages: a tiny, 3 x 3 mm 16-pin QFN which requires a user-supplied 32 kHz crystal, and an ultra-small 1.5 x 3.2 mm LCC with embedded crystal - no external crystal is required.
Serial real-time clock (RTC) with alarm functions
400 kHz I²C serial interface
Memory mapped registers for seconds, minutes, hours, day, date, month, year, and century
Tenths/hundredths of seconds register
350 nA timekeeping current at 3 V
Timekeeping down to 1.0 V
1.3 V to 4.4 V I²C bus operating voltage
4.4 V max VCCsuitable for lithium-ion battery operation
Low operating current of 35 μA (at 400 kHz I²C speed)
32 kHz square wave output is on at power-up. Suitable for driving a microcontroller in low-power mode. Can be disabled. (M41T62/64)
Programmable 1 Hz to 32 kHz square wave output (M41T62/64)
Programmable alarm with interrupt function (M41T62/65)
32 kHz crystal oscillator integrates crystal load capacitors, works with high series resistance crystals