DS1747-70

Real Time Clock Overview

The DS1747-70 is a Y2K-compliant, nonvolatile timekeeping RAM integrating a real-time clock (RTC), 512k x 8 static RAM, crystal, and lithium energy source. It operates on a 5.0V supply with an access time of 70ns. The RTC provides century, year, month, date, day, hours, minutes, and seconds in BCD format with automatic leap year compensation valid to 2100. Clock registers reside in the top eight RAM locations and are accessed via a standard byte-wide parallel interface. The device features power-fail write protection and battery voltage-level monitoring.

Real Time Clock Feature Summary

• Integrated NV SRAM, RTC, Crystal, Power-Fail Control Circuit, and Lithium Energy Source
• Y2K Compliant with Century Byte Register and Automatic Leap Year Compensation Valid to 2100
• BCD-Coded Time/Date Registers with Double Buffering for Accurate Data Access
• Power-Fail Write Protection and Battery Voltage-Level Indicator Flag

Real Time Clock Applications

• Industrial systems requiring long-term nonvolatile timekeeping
• Embedded controllers needing integrated calendar and memory
• Equipment requiring Y2K compliance without external components

Real Time Clock Procurement Notes

Verify the specific temperature grade required for the application. The DS1747-70 typically denotes the commercial range (0°C to +70°C). For industrial applications (-40°C to +85°C), the suffix IND must be included (e.g., DS1747-70IND+). Confirm RoHS compliance status based on the '+' suffix in the ordering information.

Real Time Clock Selection Notes

Select the DS1747-70 for 5.0V logic interfaces requiring 70ns access speed. Ensure the system design accommodates the 32-pin EDIP module package or the 34-pin PowerCap variant if surface mount assembly is preferred. Verify that the host microcontroller supports the parallel byte-wide interface and can manage the double-buffered register access protocol to prevent data corruption during clock updates.

Real Time Clock Part Context

The DS1747 belongs to the Maxim Integrated DS174xP family of nonvolatile timekeeping RAMs. It offers pin-for-pin compatibility with other densities in the series, allowing for density upgrades while maintaining the same footprint and interface. The device encapsulates all necessary timing components, eliminating the need for external crystals or batteries in the DIP module version.

Real Time Clock Replacement Considerations

Direct replacements within the same family include the DS1747-70IND+ for industrial temperature ranges. Other densities in the DS174xP series may serve as functional substitutes if pinout compatibility is maintained. Verify that any substitute maintains the 5.0V supply requirement and 70ns access time specifications.