M48T212V-85MH1E

Real Time Clock Overview

The M48T212V-85MH1E is a 3.3V Timekeeper supervisor integrating a real-time clock (RTC), power-fail control circuit, and battery/crystal interface. It converts external low-power SRAM into non-volatile memory via automatic backup and write protection. The device features a 44-lead SOIC package with SNAPHAT compatibility for post-reflow battery insertion. Key specifications include an 85 ns access time, 3.0V to 3.6V supply voltage range, and 16 internal registers for century, year, month, date, day, hour, minute, second, calibration, alarm, watchdog, and flags.

Real Time Clock Feature Summary

• Integrated RTC with 16-byte register map supporting BCD-coded time/date and binary control/flag data
• Automatic power-fail detection with chip deselect and write protection down to 2.7V VPFD
• Dual external chip enable outputs (E1CON, E2CON) controlling up to four parallel SRAM banks
• Programmable watchdog timer with selectable resolution and interrupt/reset steering
• SNAPHAT housing support allowing battery and crystal installation after surface mount reflow

Real Time Clock Applications

• Systems requiring non-volatile RAM expansion with integrated timekeeping
• Industrial controllers needing watchdog supervision and power-fail data retention
• Embedded devices utilizing external SRAM with automatic battery-backed backup
• Equipment requiring programmable alarms and periodic wake-up functions in battery mode

Real Time Clock Procurement Notes

Verify component status as the M48T212V series is listed as obsolete. Confirm availability of compatible SNAPHAT battery housings separately, as they are not included with the SOIC package. Ensure external SRAM selection meets voltage retention requirements below 2.0V and supports chip-enable-based deselection during power transitions.

Real Time Clock Selection Notes

Select this supervisor for 3.3V systems requiring byte-wide SRAM interfacing with RTC capabilities. Verify that the external SRAM's chip enable timing aligns with the M48T212V's propagation delays. Choose appropriate SNAPHAT battery capacity based on total retention current, including both the supervisor's IBAT and the external SRAM's retention current at the lowest operating temperature.

Real Time Clock Part Context

This part belongs to the STMicroelectronics Timekeeper family of supervisors. It specifically manages external memory while providing clock/calendar functions. The MH1E suffix indicates the 85 ns speed grade and 44-lead SOH package configuration with SNAPHAT compatibility. It serves as a bridge between microprocessors and volatile memory, ensuring data integrity during power anomalies.

Real Time Clock Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. As the product is obsolete, alternative solutions require evaluating other Timekeeper supervisors or discrete RTC/NVRAM combinations that match the 44-pin SOIC footprint and 3.3V operation.