This document introduces the features and characteristics of the M41ST84Y and M41ST84W, 5.0 or 3.0V, 512 bit (64 x8) serial RTC products.
The M41ST84Y/W Serial supervisory TIMEKEEPER® SRAM provides a 512‑bit (64 × 8) static CMOS memory with an integrated 32.768 kHz crystal‑controlled oscillator for time‑of‑day clock/calendar functions. It includes 44 bytes of general‑purpose RAM, programmable alarm, watchdog timer, square‑wave output and a power‑sense circuit that switches to a battery backup on power loss.
The device is offered in 16‑pin and 28‑pin SOIC packages, the latter with a SNAPHAT® top that integrates the lithium battery and crystal. It operates from 5.0 V or 3.0 V supplies, supports a two‑wire I²C‑compatible serial bus, and consumes only 500 nA in battery‑backup mode, making it suitable for low‑power applications.
| Operating Voltage | 5.0 V or 3.0 V |
|---|---|
| Oscillator Supply Voltage | 2.5 V to 5.5 V |
| Power‑Fail Deselect Voltage (M41ST84Y) | Voc 4.5‑5.5 V, Vprp 4.20‑4.50 V |
| Power‑Fail Deselect Voltage (M41ST84W) | Voc 2.7‑3.6 V, Vpep 2.55‑2.70 V |
| Reference Voltage | 1.25 V (for PFI/PFO) |
| Battery Backup Current | 500 nA max |
| SRAM Size | 512 bit (64 × 8) |
| General‑Purpose RAM | 44 bytes |
| Package Options | 16‑pin SOIC, 28‑pin SOIC with SNAPHAT® top |
It operates from either 5.0 V or 3.0 V supply.
The built‑in power‑sense circuit detects a loss of supply and automatically switches to the battery backup, entering an ultra‑low‑current mode.
The device draws a maximum of 500 nA in battery‑backup mode.