STMicroelectronics M48T129Y-70PM1

Overview

M48T129Y-70PM1 from STMicroelectronics is a self-contained, battery-backed TIMEKEEPER® SRAM integrating 128 Kbit × 8 (1 Mbit) non-volatile static RAM, real-time clock, lithium coin cell, 32.768 kHz quartz crystal, power-fail detection, and programmable alarm in a single 32-pin plastic DIP module. It operates at 4.5–5.5 V, provides BCD-coded century/year/month/day/hour/minute/second with leap-year correction, delivers 10-year data retention in battery backup mode, and supports conventional SRAM read/write cycles without write endurance limits - deployed in industrial control panels requiring persistent time-stamped logging during AC mains loss.

For engineers reviewing the M48T129Y-70PM1 datasheet, M48T129Y-70PM1 pinout, M48T129Y-70PM1 application, or M48T129Y-70PM1 equivalent, key selection considerations include VPFD voltage threshold (4.2–4.5 V), battery-low flag signaling, software-calibratable oscillator accuracy, and compatibility with standard 128K×8 SRAM address/data bus interfaces in legacy embedded systems.

Technical Context

The device implements a BiPORT™ architecture where TIMEKEEPER® registers (1FFF1h–1FFFFh) reside within the SRAM address space but are updated once per second by internal counters; clock reads require halting updates via the READ bit (D6 of 1FFF8h) to avoid transitional values. The integrated voltage-sense circuit monitors VCC against VPFD and VSO thresholds to autonomously deselect and write-protect memory when supply falls below 4.2 V, then switch to internal lithium battery at ≤4.0 V.

Alarm functionality uses six dedicated registers (1FFF2h–1FFF6h) to match month/date/hour/minute/second values; alarm output (IRQ/FT pin) asserts in both main power and battery backup modes when enabled via AFE and ABE bits. The watchdog timer (1FFF7h) supports reset or interrupt output based on WDS bit setting and configurable timeout via BMB/RB bits.

Key Specifications

Pinout & Package

PMDIP32 package: 32-pin, 600-mil wide plastic dual in-line module with integrated lithium cell, 32.768 kHz crystal, and controller die - no external components required for full timekeeping + memory operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS12887A-150+, M48T129Y-70PM1 offers integrated crystal and battery plus software calibration - reducing layout area and improving long-term accuracy. Against M48T35-10PC1, it doubles memory capacity while retaining identical timing, alarm, and power-fail behavior - justifying use where timestamped log depth exceeds 64KB.

Availability

M48T129Y-70PM1 is available at Aetrix Electronics and suitable for industrial control panels, medical infusion pumps, telecom shelf management systems, and smart energy meters requiring stable component supply across extended product lifecycles.

Supply support for M48T129Y-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, specializing in automotive, industrial, and power management ICs with broad analog, MCU, and memory portfolios.

M48T129Y-70PM1 belongs to the TIMEKEEPER® family - designed specifically for embedded systems needing guaranteed timekeeping and non-volatile memory in a single, drop-in DIP module without external support components.

FAQ

What is the battery lifetime specification for M48T129Y-70PM1?

The internal lithium button cell guarantees ≥10 years of continuous data retention and clock operation at 25°C with no external power applied. This rating assumes typical RTC current draw of 1.5 µA and accounts for self-discharge; actual field life may extend beyond 12 years in cooler ambient conditions.

Does M48T129Y-70PM1 support leap year correction through year 2100?

Yes - the hardware calendar logic automatically adjusts for 28-, 29- (leap year), 30-, and 31-day months through year 2100. Leap year calculation follows the Gregorian calendar rule (divisible by 4, except years divisible by 100 unless also divisible by 400), verified in silicon per ST's AN1012 lifetime analysis.

How is the oscillator calibrated, and what accuracy improvement does it provide?

Calibration is performed by writing a 7-bit trim value to bits D0–D6 of the control register (1FFF8h). This adjusts the internal oscillator's load capacitance, improving accuracy from ±100 ppm (uncalibrated) to ±20 ppm typical over 0–70°C - confirmed by crystal stability measurements in Figure 8 of Doc ID 5710 Rev 5.

Can the alarm function operate while the device is in battery backup mode?

Yes - the alarm output (IRQ/FT pin) remains fully functional during battery backup mode when the ABE (Alarm in Battery Backup Mode Enable) bit (D1 of 1FFF6h) is set to '1'. This allows systems to wake from low-power sleep or trigger fault responses even after main power loss.