STMicroelectronics M48T35Y-70PC1

Overview

M48T35Y-70PC1 from STMicroelectronics is a 5 V, 256 Kbit (32 Kb × 8) non-volatile TIMEKEEPER® SRAM integrating ultra-low-power static RAM, real-time clock, power-fail control circuitry, and on-board lithium battery + 32.768 kHz crystal in a CAPHAT™ DIP-28 package. It delivers BCD-coded timekeeping (year/month/day/hour/minute/second), automatic leap-year correction, frequency test output, and VPFD-triggered write protection. Used in industrial control panels requiring persistent time-stamped logging during mains failure.

For engineers reviewing the M48T35Y-70PC1 datasheet, M48T35Y-70PC1 pinout, M48T35Y-70PC1 application, or M48T35Y-70PC1 equivalent, this page provides verified timing accuracy (±35 ppm at 25 °C, improved to +1/–2 ppm with calibration), battery-backed data retention (>7 years), JEDEC SRAM pin compatibility, and CAPHAT™ mechanical integration details - all critical for legacy system replacement and long-life embedded design.

Technical Context

The M48T35Y-70PC1 integrates a BiPORT™ SRAM array and quartz oscillator on a single die, with clock registers mapped to upper memory addresses (7FF8h–7FFFh). Time data is stored in BCD format and updated once per second by dedicated clock logic independent of SRAM access cycles.

Its power-fail detection operates across two thresholds: VPFD (4.2–4.5 V) triggers write protection and high-Z outputs, while VSO (~4.0 V) initiates battery switchover. The STOP bit (MSB of seconds register) halts oscillator operation to conserve battery during shelf storage, and the five-bit calibration field (D4–D0 in 7FF8h) enables ±31-count periodic correction at the /256 divider stage.

Key Specifications

Pinout & Package

PCDIP28 CAPHAT™ package: 28-pin, 600 mil dual in-line package with integrated lithium button cell and 32.768 kHz quartz crystal sealed under cap. No external battery holder or crystal required.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS12887A-70IND+, M48T35Y-70PC1 offers finer RTC calibration and Y2K-compliant century handling; versus M48T59Y-70PC1, it trades memory size for lower cost and simpler integration in space-constrained legacy designs.

Availability

M48T35Y-70PC1 is available at Aetrix Electronics and suitable for industrial control panels, smart electricity meters, legacy medical devices, and building automation systems requiring stable component supply across 10+ year product lifecycles.

Supply support for M48T35Y-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, designing and manufacturing analog, MCU, power, and memory solutions for industrial, automotive, and consumer markets.

M48T35Y belongs to the TIMEKEEPER® family - engineered specifically for battery-backed time-critical data logging in industrial and utility infrastructure where long-term accuracy, JEDEC compatibility, and mechanical integration are mandatory.

FAQ

What is the battery chemistry and expected service life of M48T35Y-70PC1?

The M48T35Y-70PC1 uses a hermetically sealed 48 mAh lithium manganese dioxide (Li-MnO₂) button cell integrated within the CAPHAT™ package. Under continuous VCC loss at 25 °C, it sustains SRAM data retention and RTC operation for ≥7 years. Battery life scales inversely with ambient temperature and load; STMicroelectronics specifies 10-year shelf life at 25 °C prior to first use.

How does the M48T35Y-70PC1 handle leap years and century rollover?

The device implements hardware-based leap-year correction for February 28/29/30/31 valid through year 2100. Century rollover is managed via the CENTURY ENABLE (CEB) and CENTURY BIT (CB) in the day register (7FFCh): when CEB=1, CB toggles at 2000/2100 boundaries based on initial value; when CEB=0, CB remains static. This eliminates software intervention for Y2K compliance.

Can the M48T35Y-70PC1 be used in new designs, or is it only for legacy replacement?

M48T35Y-70PC1 remains actively manufactured and supported by STMicroelectronics with published longevity commitments. Its CAPHAT™ integration, JEDEC pin compatibility, and 70 ns access time make it suitable for both legacy drop-in replacement and new designs targeting long-lifecycle industrial equipment where proven reliability outweighs newer serial-interface alternatives.

What happens during a power failure mid-write cycle?

If VCC drops during a WRITE cycle, only the byte currently addressed may become corrupted; the remainder of the 32 Kb SRAM remains intact. The device enters data retention mode at VPFD, disabling all inputs and forcing outputs to high-Z. To prevent this, systems should monitor VCC and halt writes before entering brownout - the frequency test output and VPFD window allow predictive power-loss detection.