Design Win

5.0 V, 64 Kbit (8 Kb x 8) TIMEKEEPER® SRAM

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Product overview


The M48T58/Y TIMEKEEPER®RAM is a 8 Kb x 8 non-volatile static RAM and real-time clock. The monolithic chip is available in two special packages to provide a highly integrated battery-backed memory and real-time clock solution.

The M48T58/Y is a non-volatile pin and function equivalent to any JEDEC standard 8b Kb x 8 SRAM. It also easily fits into many ROM, EPROM, and EEPROM sockets, providing the non-volatility of PROMs without any requirement for special WRITE timing or limitations on the number of WRITEs that can be performed.

The 28-pin, 600 mil DIP CAPHAThouses the M48T58/Y silicon with a quartz crystal and a long life lithium button cell in a single package.

The 28-pin, 330 mil SOIC provides sockets with gold plated contacts at both ends for direct connection to a separate SNAPHAT®housing containing the battery and crystal. The unique design allows the SNAPHAT battery package to be mounted on top of the SOIC package after the completion of the surface mount process. Insertion of the SNAPHAT housing after reflow prevents potential battery and crystal damage due to the high temperatures required for device surface-mounting. The SNAPHAT housing is keyed to prevent reverse insertion. The SOIC and battery/crystal packages are shipped separately in plastic anti-static tubes or in tape & reel form.

For the 28-lead SOIC, the battery/crystal package (e.g., SNAPHAT) part number is “M4T28-BR12SH”.

  • All features

    • Integrated, ultra low power SRAM, real-time clock, power-fail control circuit and battery
    • BYTEWIDERAM-like clock access
    • BCD coded year, month, day, date, hours, minutes, and seconds
    • Frequency test output for real-time clock
    • Automatic power-fail chip deselect and WRITE protection
    • WRITE protect voltages (VPFD= power-fail deselect voltage):
      • M48T58: VCC= 4.75 to 5.5 V; 4.5 V ≤ VPFD≤ 4.75 V
      • M48T58Y: VCC= 4.5 to 5.5 V; 4.2 V ≤ VPFD≤ 4.5 V
    • Self-contained battery and crystal in the CAPHATDIP package
    • Packaging includes a 28-lead SOIC and SNAPHAT® top (to be ordered separately)
    • SOIC package provides direct connection for a snaphat housing containing the battery and crystal
    • Pin and function compatible with JEDEC standard 8 Kb x 8 SRAMs
    • RoHS compliant
      • Lead-free second level interconnect

Circuit Diagram

EDA Symbols, Footprints and 3D Models

STMicroelectronics - M48T58

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Quality and Reliability

Part Number Marketing Status Package Grade RoHS Compliance Grade Material Declaration**
PDIP 28 .7 Industrial Ecopack2



PDIP 28 .7

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PDIP 28 .7



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(**) The Material Declaration forms available on st.com may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.

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