STMicroelectronics M48T35Y-70MH1E

Overview

M48T35Y-70MH1E 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 quartz crystal in a CAPHAT™ DIP-28 package. It provides 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 AC brownouts.

For engineers reviewing the M48T35Y-70MH1E datasheet, M48T35Y-70MH1E pinout, M48T35Y-70MH1E application, or M48T35Y-70MH1E equivalent, this page delivers verified timing accuracy (±35 ppm @ 25°C, improved to +1/–2 ppm with calibration), battery-backed data retention (>7 years), JEDEC 32 Kb × 8 SRAM compatibility, and CAPHAT™ mechanical integration details - all critical for legacy system replacement and long-life embedded design.

Technical Context

The M48T35Y-70MH1E integrates a BiPORT™ SRAM array and a quartz-controlled oscillator on a single die, with clock registers mapped to upper memory addresses (7FF8h–7FFFh) for byte-wide access via standard SRAM read/write cycles. Its power-fail detection operates within a defined VPFD window (4.2 V ≤ VPFD ≤ 4.5 V), triggering automatic chip deselect and write protection before switchover to internal battery at VSO.

Timekeeping uses BCD-encoded registers updated once per second by dedicated clock logic; the STOP bit (MSB of seconds register) halts oscillation to conserve battery during shelf storage, and calibration bits (D4–D0 in 7FF8h) enable ±31-count periodic correction at the ÷256 stage to compensate for crystal temperature drift - eliminating external trim capacitors.

Key Specifications

Pinout & Package

Package: PCDIP28 (28-pin plastic DIP, 600 mil width) with integrated CAPHAT™ housing containing lithium button cell and 32.768 kHz crystal.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS12887A-70+, M48T35Y-70MH1E reduces bill-of-materials and layout risk via integrated CAPHAT™; versus M48T59Y-70MH1E, it offers optimal cost/performance balance for 256 Kbit logging needs while retaining identical timing architecture and calibration capability.

Availability

M48T35Y-70MH1E is available at Aetrix Electronics and suitable for industrial control panels, medical device event logging, legacy POS terminal upgrades, and smart energy metering requiring stable component supply over 10+ year product lifecycles.

Supply support for M48T35Y-70MH1E 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, designing and manufacturing microcontrollers, power management ICs, sensors, and timing solutions for industrial, automotive, and consumer markets.

The M48T35Y belongs to ST's TIMEKEEPER® family - engineered specifically for robust, long-life, battery-backed timekeeping and non-volatile data storage in mission-critical embedded systems where power resilience and calendar accuracy are essential.

FAQ

What is the function of the CAPHAT™ package in M48T35Y-70MH1E?

The CAPHAT™ package is a proprietary STMicroelectronics DIP-28 housing that integrates the silicon die, a 32.768 kHz quartz crystal, and a long-life lithium button cell into a single, factory-assembled unit. This eliminates external battery holders, crystal load capacitors, and PCB routing for backup power - reducing design complexity, improving reliability, and enabling direct socket replacement of legacy SRAMs.

How does the M48T35Y-70MH1E handle leap years and month-end date rollovers?

The M48T35Y-70MH1E performs fully autonomous date arithmetic in hardware: it correctly advances from February 28 to March 1 in common years, February 29 to March 1 in leap years (including century years divisible by 400), and handles 30- vs. 31-day months without firmware involvement. This behavior is fixed in silicon and validated through year 2100 per the documented century bit (CB) and century enable bit (CEB) logic.

Can the internal battery be replaced after soldering?

No - the CAPHAT™ package used in M48T35Y-70MH1E is a sealed, non-serviceable unit with the lithium cell permanently bonded inside the DIP-28 housing. Battery replacement is not possible post-assembly; the device is rated for ≥7 years of data retention under specified conditions, and end-of-life requires full component replacement.

What is the purpose of the frequency test (FT) bit in the seconds register?

Bit D6 (FT) in register 7FFFh enables a 32.768 kHz square wave output on the DQ6 pin, allowing direct oscilloscope verification of oscillator operation during system bring-up or failure analysis. The FT bit must be set to '0' during normal operation to prevent interference with timekeeping registers and ensure correct RTC functionality per the datasheet specification.