STMicroelectronics M48T128Y-70PM1

Overview

M48T128Y-70PM1 from STMicroelectronics is a 5.0 V, 1 Mbit (128 Kb × 8) TIMEKEEPER® SRAM integrating ultra-low-power static RAM, real-time clock, power-fail control, lithium battery, and 32.768 kHz quartz crystal in a single 32-pin DIP module. It functions as a pin- and function-compatible replacement for JEDEC-standard 128 K × 8 SRAMs while delivering non-volatile timekeeping and data retention. Key confirmed specs include 70 ns access time, BCD-coded calendar/time registers (year–second), VPFD = 4.1–4.5 V power-fail deselect threshold, and 10-year battery-backed data/clock retention at room temperature - deployed in industrial control panels requiring timestamped event logging during mains failure.

For engineers reviewing the M48T128Y-70PM1 datasheet, M48T128Y-70PM1 pinout, M48T128Y-70PM1 application, or M48T128Y-70PM1 equivalent, this page delivers verified technical context on its BiPORT™ register architecture, software-controlled clock calibration (±1/–2 ppm accuracy), power-fail switchover behavior (VSO threshold), and SRAM timing compliance - all critical for legacy system maintenance, embedded time-stamping, and battery-backed memory migration.

Technical Context

The M48T128Y-70PM1 implements a dual-domain architecture: a conventional 131,072 × 8 SRAM array with standard E/G/W control logic, and a dedicated TIMEKEEPER subsystem where seven BCD-formatted clock registers (1FFF8h–1FFFFh) reside within the same address space but are updated once per second by an independent oscillator chain. The 32.768 kHz crystal drives a divider with programmable calibration at the ÷128 stage using five bits (D4–D0) plus sign bit (D5) in the control register.

Its power management uses analog voltage sensing to detect VCC decay: when VCC falls between VPFD (min) = 4.1 V and VPFD (max) = 4.5 V, it asserts write protection and high-Z outputs; below VSO (~4.0 V), it seamlessly switches to internal lithium cell supply. The STOP bit (D7 of 1FFF9h) allows manual oscillator disable to conserve battery during shelf storage - shipped default-enabled.

Key Specifications

Pinout & Package

Package: 32-pin plastic DIP (PMDIP32), 600 mil width, hybrid module containing SRAM die, clock controller, quartz crystal, and lithium battery.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar battery-backed timekeeping SRAM applications.

Compared with DS12887A-150+, M48T128Y-70PM1 offers tighter timing (70 ns vs. 150 ns) and field-calibratable RTC; versus M48T35-70PC1, it doubles SRAM capacity for extended data buffering - making it optimal for applications demanding both high-resolution timekeeping and robust local storage.

Availability

M48T128Y-70PM1 is available at Aetrix Electronics and suitable for industrial control panels, medical device event loggers, and legacy POS terminals requiring stable component supply amid ongoing obsolescence transitions.

Supply support for M48T128Y-70PM1 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, power management ICs, sensors, and analog/mixed-signal devices for industrial, automotive, and consumer markets.

The TIMEKEEPER® product line was developed specifically to integrate battery-backed SRAM and high-accuracy RTC functionality into compact, self-contained modules - targeting legacy system upgrades and applications where time-stamped non-volatility is mission-critical.

FAQ

Is M48T128Y-70PM1 still in production despite being "not recommended for new design"?

Yes. STMicroelectronics continues manufacturing M48T128Y-70PM1 as a production part, though it is marked "not recommended for new designs" due to newer alternatives like the M48Txx series with enhanced features. Aetrix Electronics maintains active inventory and supports long-term supply for legacy system maintenance and repair programs.

How does the BiPORT™ register architecture affect firmware access to clock data?

BiPORT™ allows simultaneous access to SRAM and TIMEKEEPER registers using the same address/data bus: clock registers occupy fixed addresses 1FFF8h–1FFFFh within the SRAM map. Firmware reads/writes them identically to memory locations - no special I²C/SPI protocol required - but must halt updates (via READ bit D6) before reading to avoid transitional values.

What is the significance of the VPFD voltage range (4.1–4.5 V) in system design?

VPFD defines the window where the device autonomously initiates write protection and high-Z outputs to prevent data corruption during brownout. Designers must ensure system power rails decay smoothly through this range - rapid transients may cause spurious deselect - and use ≥0.1 µF ceramic decoupling near VCC to suppress noise-induced false triggers.

Can the internal lithium battery be replaced if depleted?

No. The lithium button cell is sealed inside the PMDIP32 hybrid package and not user-serviceable. Battery life is rated for ≥10 years at 25 °C under continuous backup operation; actual longevity depends on ambient temperature and frequency of VCC interruptions. End-of-life requires full module replacement.