M41T82, M41T83 2 Serial I C bus real-time clock (RTC) with battery switchover Datasheet - production data nd Optional 2 programmable alarm available Square wave output defaults to 32 KHz on power-up (M41T83 only) QFN16 (4 mm x 4 mm) RESET (RST) output Watchdog timer Programmable 8-bit counter/timer 7 bytes of battery-backed user SRAM SO8 (4.90 mm x 3.90 mm) Battery low flag Low operating current of 80 A Oscillator stop detection 18 Battery or SuperCap backup Operating temperature of 40 C to 85 C 1 Package options SOX18, embedded crystal a 16-lead QFN (M41T83) (11.61 mm x 7.62 mm) an 8-lead SOIC (M41T82) or an 18-lead embedded crystal SOIC (M41T83) Features RoHS compliance: lead-free components are Ultra-low battery supply current of 365 nA compliant with the RoHS directive Factory-calibrated accuracy of 5 ppm typical after 2 reflows (SOX18) Much better accuracies achievable using built-in programmable analog and digital calibration circuits 2.0 V to 5.5 V clock operating voltage Counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century Automatic switchover and reset output circuitry (fixed reference) M41T83S: V = 3.00 V to 5.50 V CC M41T83R: V = 2.70 V to 5.50 V CC M41T83Z: V = 2.38 V to 5.50 V CC 2 Serial interface supports I C bus (400 kHz protocol) Programmable alarm with interrupt function (valid even during battery backup mode) June 2015 DocID012578 Rev 18 1/64 This is information on a product in full production. www.st.com 64Contents M41T82, M41T83 Contents 1 Description . 6 2 Operation . 12 2.1 2-wire bus characteristics . 13 2.1.1 Bus not busy . 13 2.1.2 Start data transfer . 13 2.1.3 Stop data transfer . 13 2.1.4 Data valid 13 2.1.5 Acknowledge . 14 2.2 Read mode 15 2.3 Write mode 17 2.4 Data retention and battery switchover (V = V ) 18 SO RST 2.5 Power-on reset (t ) . 18 rec 3 Clock operation 19 3.1 Clock data coherency 20 3.1.1 Example of incoherency 20 3.1.2 Accessing the device . 21 3.2 Halt bit (HT) operation . 21 3.2.1 Power-down time-stamp 22 3.3 Real-time clock accuracy . 27 3.4 Clock calibration 28 3.4.1 Digital calibration (periodic counter correction) . 28 3.4.2 Analog calibration (programmable load capacitance) 31 3.4.3 Pre-programmed calibration value . 32 3.5 Setting the alarm clock registers . 36 3.6 Optional second programmable alarm and user SRAM 37 3.7 Watchdog timer 37 3.8 8-bit (countdown) timer . 38 3.8.1 M41T83 timer interrupt/output 38 3.8.2 Timer flag (TF) 40 3.8.3 Timer interrupt enable (TIE, M41T83 only) 40 3.8.4 Timer enable (TE) . 40 2/64 DocID012578 Rev 18