STMicroelectronics M48T58-70PC1

Overview

M48T58-70PC1 from STMicroelectronics is a 5.0 V, 64 Kbit (8 Kb × 8) TIMEKEEPER® SRAM integrating non-volatile static RAM, real-time clock, power-fail control circuitry, and a self-contained lithium battery and quartz crystal in a CAPHAT™ DIP package. It provides BCD-coded time/date registers (year, month, day, date, hours, minutes, seconds), frequency test output (FT), automatic write protection during V_CC brownout, and pin/function compatibility with JEDEC-standard 8 Kb × 8 SRAMs for drop-in replacement in legacy systems requiring persistent timekeeping and memory.

For engineers reviewing the M48T58-70PC1 datasheet, M48T58-70PC1 pinout, M48T58-70PC1 application, or M48T58-70PC1 equivalent, this device serves as a single-chip solution for battery-backed RTC + SRAM in industrial control panels, medical instrumentation, point-of-sale terminals, and telecom infrastructure where data retention during power loss and accurate time stamping are critical design requirements.

Technical Context

The M48T58-70PC1 integrates a 32.768 kHz quartz oscillator, BiPORT™ dual-port RAM array (8184 × 8), voltage-sense switching circuitry, and lithium cell management on a single die. Its clock chain updates eight dedicated BCD time registers (addresses 1FF8h–1FFFh) once per second, while the SRAM operates identically to standard CMOS SRAM under normal V_CC conditions.

Power-fail detection triggers at VPFD = 4.5 V ≤ VPFD ≤ 4.75 V (M48T58 variant), initiating automatic chip deselect, high-Z I/O, and seamless switchover to internal battery when V_CC drops below V_SO. The STOP bit (MSB of seconds register) halts oscillator operation to extend battery life, and the READ/WRITE bits in control register 1FF8h enable atomic clock register access without disrupting ongoing timekeeping.

Key Specifications

Pinout & Package

PCDIP28 CAPHAT™ package: 28-pin plastic dual in-line package with integrated lithium battery and quartz crystal housed within the molded cap.

Key Features

Applications

Equivalent & Alternatives

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

Compared with DS1687-5+, M48T58-70PC1 offers superior integration via embedded crystal/battery in DIP format, simplifying legacy through-hole upgrades; versus M48T35Y-70PC1, it doubles SRAM capacity for larger log buffers or multi-zone timekeeping without changing footprint or firmware interface.

Availability

M48T58-70PC1 is available at Aetrix Electronics and suitable for industrial control panels, medical diagnostic equipment, point-of-sale terminals, and telecom network elements requiring stable component supply across long product lifecycles and extended obsolescence windows.

Supply support for M48T58-70PC1 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 microcontrollers, power management ICs, sensors, and analog/mixed-signal products for industrial, automotive, and consumer markets.

The TIMEKEEPER® product line targets applications demanding guaranteed timekeeping and non-volatile memory in harsh or mission-critical environments, emphasizing integration, long-term reliability, and regulatory compliance for industrial automation and healthcare systems.

FAQ

What is the function of the FT (frequency test) pin?

The FT pin provides an open-drain 32.768 kHz square wave output directly from the internal quartz oscillator. It enables real-time verification of oscillator functionality during system bring-up or field diagnostics without requiring access to internal registers or clock circuitry. This signal is active whenever the oscillator is running, including during battery backup mode, and can drive logic-level inputs or oscilloscope probes for frequency accuracy measurement.

How does the M48T58-70PC1 handle leap years and century rollover?

The M48T58-70PC1 automatically adjusts for 28-, 29- (leap year), 30-, and 31-day months using internal calendar logic. For century rollover, the Century Enable Bit (CEB) and Century Bit (CB) in register 1FF8h allow explicit control: when CEB=1, CB toggles at year 2000/2100 boundaries based on initial state, enabling correct BCD year interpretation beyond 2099 per application note AN923.

Can the internal battery be replaced after soldering?

No - the CAPHAT™ DIP package permanently encapsulates the lithium button cell and crystal within the molded cap. Battery replacement is not user-serviceable; the entire device must be replaced upon end-of-life. ST specifies ≥7 years of data retention under continuous battery backup, and the part is intended for applications where field battery service is impractical or prohibited by safety certification.

Is the M48T58-70PC1 compatible with 3.3 V systems?

No - the M48T58-70PC1 is specified only for 4.75–5.5 V operation and lacks 3.3 V tolerance. Its VPFD threshold (4.5–4.75 V) and internal regulator design require stable 5 V supply. Interfacing with 3.3 V microcontrollers necessitates level-shifting on address/data/control lines and separate 5 V rail generation; no internal voltage translation is provided.