DS1742-70+

Real Time Clock Overview

The DS1742-70+ is a Y2K-compliant nonvolatile timekeeping RAM integrating a real-time clock/calendar and 2k x 8 static RAM. It operates at 5V with a 70ns access time in a 24-pin EDIP package. The device features BCD-coded registers for century, year, month, date, day, hours, minutes, and seconds, including automatic leap year compensation valid until 2100. Clock registers reside in the top eight RAM locations and are accessed via a standard JEDEC bytewide interface. Internal lithium energy provides over 10 years of data retention without VCC.

Real Time Clock Feature Summary

• Integrated RTC, NV SRAM, crystal, power-fail control, and lithium battery
• Automatic leap year compensation and BCD-coded time/date registers
• Double-buffered clock registers prevent data corruption during updates
• Power-fail write protection ensures data integrity during voltage drops

Real Time Clock Applications

• Industrial systems requiring precise timekeeping and data logging
• Embedded controllers needing nonvolatile memory with calendar functions
• Equipment requiring Y2K compliance and long-term data retention

Real Time Clock Procurement Notes

Verify component authenticity through authorized distributors or manufacturer channels. Confirm RoHS compliance status as indicated by the '+' suffix. Ensure proper handling to avoid electrostatic discharge damage during installation. Check for lead-free certification documentation if required by regulatory standards.

Real Time Clock Selection Notes

Select the DS1742-70+ for commercial temperature range applications (0°C to +70°C). Choose the -100 variant for slower system buses requiring 100ns access times. Consider the IND version for industrial environments (-40°C to +85°C). Verify voltage requirements match the 5V specification; 3.3V variants are available separately.

Real Time Clock Part Context

The DS1742 belongs to the Maxim Integrated DS1742 family of nonvolatile timekeeping RAMs. It shares architectural similarities with other members like the DS1743 and DS1747 but offers specific capacity and pinout configurations. This component represents a solution combining memory and clock functions in a single DIP package.

Real Time Clock Replacement Considerations

Direct replacements include DS1742-100+ for slower timing requirements. Industrial grade equivalent is DS1742-100IND+. For higher density needs, consider DS1743 series. Verify pin compatibility and voltage levels before substitution.

Real Time Clock FAQ

How does the DS1742 handle leap years?

The device automatically compensates for leap years up to the year 2100 using its internal logic, eliminating the need for software correction.

What happens when VCC drops below the power fail point?

Write protection activates, blocking access to prevent data corruption. Power switches to the internal lithium battery to maintain RTC operation and SRAM data.

Can the clock oscillator be stopped to save battery?

Yes, setting the OSC bit (bit 7 of the seconds register) to logic 1 stops the oscillator, minimizing current drain from the backup battery.