The M41T81 is a low-power serial real-time clock with a built-in 32.768 kHz oscillator controlled by an external crystal. It provides counters for tenths/hundredths of seconds, seconds, minutes, hours, day, date, month, year, and century, and uses eight bytes of SRAM for the clock/calendar function in BCD format. The device has a two-line serial interface and automatically switches to the battery supply when VCC falls below the power-down trip point.
The datasheet covers operation, 2-wire bus characteristics, READ and WRITE modes, clock registers, calibration, alarm registers, watchdog timer, square wave output, maximum ratings, DC and AC parameters, package information, and part numbering. The document is dated June 2010, Doc ID 7529 Rev 10, and states that the M41T81 is not recommended for new designs; ST directs new non-automotive designs to the M41T81S.
| Clock operating voltage | 2.0 to 5.5 V |
|---|---|
| Operating temperature | -40 to 85 °C |
| Battery supply current | 0.6 UA typ at 3 V |
| Crystal oscillator | 32 KHz, 12.5 pF load capacitance |
| Package | 8-pin SOIC |
| Watchdog timer range | 62.5 ms to 128 s |
The M41T81 has a clock operating voltage of 2.0 to 5.5 V.
The M41T81 is supplied in an 8-pin SOIC package.
It has a programmable watchdog timer from 62.5 ms to 128 s.
No. The datasheet states it is not recommended for new design and directs new non-automotive designs to the M41T81S.