STMicroelectronics M48T12-70PC1

Overview

M48T12-70PC1 from STMicroelectronics is a 5.0 V, 16 Kbit (2 Kb × 8) non-volatile TIMEKEEPER® SRAM integrating ultra-low-power static RAM, real-time clock, and power-fail control circuitry in a single CAPHAT™ DIP package. It delivers BCD-coded timekeeping (year/month/day/hour/minute/second), ±1 minute/month accuracy at 25 °C, software-controlled clock calibration, and automatic WRITE protection during VCC decay - used in industrial control panels, embedded data loggers, and legacy system RTC upgrades requiring battery-backed time and memory.

For engineers reviewing the M48T12-70PC1 datasheet, M48T12-70PC1 pinout, M48T12-70PC1 application, or M48T12-70PC1 equivalent, this page provides verified technical context, JEDEC-compatible SRAM timing, VPFD voltage thresholds, register-mapped clock access, and validated alternatives for time-critical, long-life backup memory designs.

Technical Context

The M48T12-70PC1 integrates a 2048 × 8 BiPORT™ SRAM array with a 32.768 kHz quartz oscillator, voltage-sense switching circuitry, and lithium battery within a single 24-pin PCDIP24 CAPHAT™ package. Its clock registers (7F8h–7FFh) reside in upper SRAM addresses and are updated once per second by dedicated hardware - not CPU-driven - ensuring atomic time updates independent of host read/write activity.

Power management is handled autonomously: when VCC drops between 4.2 V and 4.5 V (VPFD window), the device enters write-protected deselect mode; below ~3 V, it seamlessly switches to battery backup while maintaining clock operation and SRAM retention for ≥10 years. The BOK (Battery OK) flag signals low battery condition on power-up, blocking first WRITE until cleared.

Key Specifications

Pinout & Package

Package: PCDIP24 - 24-pin plastic dual in-line package with integrated lithium battery and 32.768 kHz quartz crystal in CAPHAT™ configuration. Dimensions: 600 mil width, 0.3 inch row spacing, standard DIP footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar non-volatile timekeeping memory applications.

Compared with DS1642-120IND+, M48T12-70PC1 offers tighter clock accuracy and field calibration; compared with M48T35Y-70PC1, it provides optimal cost/performance for 2K×8 applications without over-provisioning memory or complexity.

Availability

M48T12-70PC1 is available at Aetrix Electronics and suitable for industrial control panels, embedded data loggers, and legacy system RTC upgrades requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for M48T12-70PC1 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, specializing in microcontrollers, analog ICs, MEMS, and power management solutions for industrial, automotive, and consumer markets.

M48T12-70PC1 belongs to the TIMEKEEPER® family - designed specifically to integrate battery-backed SRAM and precision RTC functionality into compact, self-contained packages for mission-critical timekeeping in resource-constrained embedded systems.

FAQ

What is the function of the BOK (Battery OK) flag?

The BOK flag is a hardware status bit set automatically on power-up if the internal lithium battery voltage falls below specification. It blocks the first WRITE operation until cleared by successfully writing data - preventing corrupted time or memory writes due to insufficient backup power. The flag clears after the first successful WRITE and does not reassert unless battery voltage drops again during subsequent power cycles.

How is clock calibration performed in the M48T12-70PC1?

Calibration is implemented via a 5-bit signed value stored in bits 0–4 of the control register (7F8h). Bit 5 is the sign bit: '1' enables positive calibration (+4.068 ppm per step), '0' enables negative (–2.034 ppm per step). Each adjustment modifies the oscillator divider every 64 minutes, allowing fine-tuning across ±5.5 minutes/month - configured entirely in software without external components.

Can the M48T12-70PC1 be used in place of a standard 2K×8 SRAM without modification?

Yes - it is pin- and function-compatible with JEDEC-standard 2K×8 SRAMs. When VCC is stable and the clock is disabled (STOP bit = 1), it behaves identically to a conventional SRAM. All standard READ/WRITE timing (tAVQV = 70 ns, tWLWH = 50 ns) is met, and unused upper addresses (7F8h–7FFh) default to standard memory behavior unless explicitly accessed for timekeeping.

What happens during a power failure while a WRITE cycle is active?

If VCC drops into the VPFD window (4.2–4.5 V) mid-WRITE, the device halts the cycle, places outputs in Hi-Z, and write-protects the SRAM - but data at the currently addressed location may become corrupted. Other memory locations remain intact. To mitigate risk, systems should monitor the BOK flag and avoid initiating WRITEs during brownout conditions, or use the READ bit to halt clock updates before critical writes.