ST M41T83ZQA6F

The M41T8x is a low-power serial I2C RTC with an integrated 32.768 kHz oscillator (QFN16 and SO8 packages require an external crystal, while the SOX18 package has a built-in crystal). Eight bytes of the register map are configured in binary-coded decimal (BCD) format to provide clock/calendar functions. An additional 17 bytes of the register map provide status/control for two alarms, a watchdog, an 8-bit counter, and a square wave output. Seven bytes of user-accessible SRAM are also available. Address and data are transferred serially through a two-wire bidirectional I2C interface. The internal address register increments automatically after each write or read operation. The M41T8x features an integrated power-sense circuit that detects power failure and automatically switches to battery backup upon power loss. During a power failure, a small lithium coin cell battery supplies the energy needed to keep the clock running. User-accessible functions include one non-volatile timekeeping clock/calendar, two alarm interrupts, a watchdog timer, a programmable 8-bit counter, and a square wave output. The eight clock address locations cover century, year, month, date, day-of-week, hours, minutes, seconds, 1/10 seconds, and 1/100 seconds, all in 24-hour BCD format. The system automatically corrects the number of days in a month for 28, 29 (leap year), 30, and 31 days. The M41T83 is available in a QFN16 or SOX18 300 mil SOIC package with an integrated 32 kHz crystal. The SOX18 package requires only a user-supplied battery for non-volatile operation. The M41T82 is available in an SO8 package only.

• Ultra-low battery supply current: 365 nA
• Factory-calibrated accuracy: ±5 ppm after 2 reflows (SOX18)
• Higher accuracy achievable via built-in programmable analog and digital calibration circuits
• Clock operating voltage: 2.0 V to 5.5 V
• Timekeeping registers for 1/100 second, 1/10 second, seconds, minutes, hours, day of week, date, month, year, and century
• Automatic battery switchover and reset output circuit (fixed reference)
• M41T83S: VCC = 3.00 V to 5.50 V; M41T83R: VCC = 2.70 V to 5.50 V; M41T83Z: VCC = 2.38 V to 5.50 V
• Serial interface supports I2C bus (400 kHz protocol)
• Programmable alarm with interrupt function (active even in battery backup mode)
• Optional second programmable alarm
• Square wave output defaults to 32 kHz after power-up (M41T83 only)