STMicroelectronics M48T37Y-70MH1F

Overview

M48T37Y-70MH1F from STMicroelectronics is a monolithic TIMEKEEPER® SRAM integrating 256 Kbit (32 K × 8) non-volatile static RAM, real-time clock, power-fail control circuitry, watchdog timer, and battery-switchover logic in a single 44-pin SOIC package. It operates at 5.0 V (V_CC = 4.5–5.5 V), features VPFD = 4.2–4.5 V power-fail deselect, supports BCD-format timekeeping with automatic leap-year correction, and delivers ≥7 years data retention on internal lithium backup. It is used in industrial control panels requiring persistent time-stamped logging during mains failure.

For engineers reviewing the M48T37Y-70MH1F datasheet, M48T37Y-70MH1F pinout, M48T37Y-70MH1F application, or M48T37Y-70MH1F equivalent, key selection considerations include its integrated crystal/battery SNAPHAT® top compatibility (e.g., M4T28-BR12SH), 70 ns read/write cycle timing, alarm interrupt capability in battery-backup mode, and microprocessor power-on reset assertion valid even during V_CC loss.

Technical Context

The device implements a dual-domain architecture: a 32,752 × 8 BiPORT™ SRAM array for user data and dedicated TIMEKEEPER registers (addresses 7FF1h–7FFFh) updated once per second by an on-chip 32.768 kHz oscillator. Clock registers store century, year, month, date, day, hour, minute, and second in 24-hour BCD format with automatic month-length correction including leap years through 2100.

Its power management includes voltage-sense circuitry that triggers write protection when V_CC falls into the 4.2–4.5 V VPFD window, switches to internal lithium battery below V_SO, and asserts open-drain RST and IRQ/FT outputs. The watchdog timer uses programmable multiplier/resolution bits (7FF7h) and generates reset or interrupt via WDI input or internal timeout.

Key Specifications

Pinout & Package

Package: 44-pin plastic small outline (SOH44), 330 mil width, with gold-plated sockets for mating SNAPHAT® top (e.g., M4T28-BR12SH). SNAPHAT® contains 32.768 kHz crystal and 48 mAh lithium coin cell; mounted post-reflow to avoid thermal damage.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar real-time clock + non-volatile memory applications.

Compared with DS12887A, M48T37Y-70MH1F reduces bill-of-materials count by integrating crystal, battery, and power-fail logic-cutting layout area by 35% and eliminating solder joint reliability risks associated with discrete battery holders. Unlike AD7940TRZ, it delivers complete timekeeping + memory functionality in one die.

Availability

M48T37Y-70MH1F is available at Aetrix Electronics and suitable for industrial control panels, energy meter data loggers, medical diagnostic equipment, and network infrastructure nodes requiring stable component supply across extended product lifecycles.

Supply support for M48T37Y-70MH1F includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, analog ICs, MEMS, and power management solutions for industrial, automotive, and consumer markets.

M48T37Y-70MH1F belongs to the TIMEKEEPER® family-engineered specifically for applications demanding tightly coupled, battery-backed real-time clock and non-volatile memory in a single package, minimizing system-level timing uncertainty and firmware complexity.

FAQ

What is the purpose of the SNAPHAT® top, and is it included with M48T37Y-70MH1F?

The SNAPHAT® top (e.g., M4T28-BR12SH) contains the 32.768 kHz crystal and 48 mAh lithium coin cell, and mounts directly onto the SOH44 package after reflow soldering to avoid thermal damage. It is not included with M48T37Y-70MH1F-the SOIC and SNAPHAT® are shipped separately in anti-static tubes or tape-and-reel. Mounting is keyed to prevent reverse insertion.

How does the M48T37Y-70MH1F handle leap years and month-length variations?

Hardware calendar logic automatically adjusts for 28-, 29- (leap year), 30-, and 31-day months without firmware involvement. Leap-year calculation is valid through year 2100 and is implemented in the on-die clock chain-not in SRAM registers-ensuring accuracy persists across power cycles and battery backup transitions.

Can the alarm function operate while the device is powered solely by the internal battery?

Yes. The alarm circuit remains fully active in battery-backup mode. When alarm registers (7FF2h–7FF5h) match current RTC values, IRQ/FT asserts active-low-even with V_CC = 0 V-enabling wake-up of sleeping microcontrollers or triggering external latching circuits for maintenance alerts.

What is the significance of the VPFD voltage range (4.2–4.5 V) for M48T37Y-70MH1F?

VPFD defines the voltage window where the device autonomously disables writes and places all I/O in high-impedance state to prevent data corruption during brownout. At 4.2 V ≤ V_CC ≤ 4.5 V, SRAM enters write-protected mode while continuing to serve read requests-ensuring data integrity without requiring host MCU intervention or external supervisor ICs.