M48T212V-85MH1F

Real Time Clock Overview

The M48T212V-85MH1F is an obsolete 3.3V Timekeeper supervisor integrating a real-time clock (RTC), power-fail control, and external SRAM management. It converts low-power SRAMs into non-volatile memory via automatic backup switching at the VSO threshold. The device features a 44-lead SOIC package with SNAPHAT compatibility for battery and crystal integration. Key specifications include 85 ns access time, 3.0V to 3.6V supply voltage, and operation within 0°C to 70°C. It provides 16 TIMEKEEPER registers for calendar, alarm, watchdog, and flag functions.

Real Time Clock Feature Summary

• Integrated RTC with programmable alarms, watchdog timer, and century/year/date/time tracking
• Automatic power-fail detection and write protection for attached external SRAMs
• SNAPHAT housing support for top-mounted lithium battery and crystal without thermal damage
• Microprocessor power-on reset and two external chip enable outputs (E1CON, E2CON)

Real Time Clock Applications

• Systems requiring non-volatile RAM conversion using external CMOS SRAMs
• Industrial controllers needing watchdog timer and power-fail safety mechanisms
• Embedded devices requiring precise calendar and alarm functionality in 3.3V environments

Real Time Clock Procurement Notes

This component is officially listed as an Obsolete Product by STMicroelectronics. Verification of availability should focus on distributor surplus or secondary market sources rather than standard manufacturing channels. Ensure that any acquired units are compatible with the required 44-lead SOH44 package and SNAPHAT interface specifications.

Real Time Clock Selection Notes

Select this part only if the system design specifically requires the integrated supervisor functions combined with external SRAM control. Verify that the external SRAMs selected meet the data retention requirements down to 2.0V and have chip enable inputs that disable all other inputs during power failure. Confirm that the 3.0V to 3.6V operating range aligns with the target system's power supply rails.

Real Time Clock Part Context

The M48T212V belongs to the Timekeeper series of supervisors from STMicroelectronics. It is designed to work in conjunction with external static RAMs to create cost-effective non-volatile memory solutions. The '85' suffix indicates an 85 ns access speed, while 'MH1F' denotes the specific tape-and-reel packaging and lead-free composition for the 44-lead SOIC variant.

Real Time Clock Replacement Considerations

As an obsolete product, direct replacements may not be available from the original manufacturer. Designers should evaluate modern RTC supervisors or integrated NVRAM solutions that offer similar pin counts and functionality. Cross-reference with newer STTimekeeper models or alternative vendors providing integrated RTC and SRAM management in a single package.

Real Time Clock FAQ

How does the M48T212V protect external SRAM data during power failure?

The device monitors the VCC supply voltage. When VCC falls below the power-fail deselect voltage (VPFD), it automatically inhibits access to the external SRAM by driving the E1CON and E2CON outputs high, effectively write-protecting the memory until normal power is restored.

What is the function of the SNAPHAT housing?

The SNAPHAT housing holds the lithium battery and crystal oscillator. It is designed to be mounted on top of the SOIC package after surface mount reflow, preventing thermal damage to the battery and crystal components during the soldering process.

Can the alarm interrupt function in battery backup mode?

Yes, the alarm interrupt can function in battery backup mode if the Alarm in Battery Back-up Mode Enable bit (ABE) and the Alarm Flag Enable bit (AFE) are both set. In this state, the IRQ/FT pin will go low when an alarm condition occurs.