DS1643-100

Real Time Clock Overview

The DS1643-100 is a nonvolatile static RAM integrated with a real-time clock, crystal, and lithium energy source. It provides 8K x 8 byte-wide memory accessible via standard parallel interfaces (85ns or 100ns access times). The RTC maintains year, month, date, day, hours, minutes, and seconds in BCD format with automatic leap year compensation valid through 2100. Clock registers reside in the top eight RAM locations and are double-buffered to prevent data corruption during updates. The device includes power-fail write protection for ±10% VCC tolerance and ensures over 10 years of data retention without power.

Real Time Clock Feature Summary

• Integrated NV SRAM, Real-Time Clock, Crystal, Power-Fail Control Circuit, and Lithium Energy Source
• BCD-Coded Timekeeping with Leap Year Compensation Valid Up to 2100
• Power-Fail Write Protection Allows for ±10% VCC Power Supply Tolerance
• Lithium Energy Source Electrically Disconnected Until First Power Application

Real Time Clock Applications

• Systems requiring read/write nonvolatility and real-time clock functionality
• Substitution in ROM, EPROM, and EEPROM sockets
• Data logging applications needing time-stamped storage

Real Time Clock Procurement Notes

Verify the specific suffix (+) indicates lead-free/RoHS-compliant packaging. Confirm the package type matches the design requirements, as the -100 variant typically corresponds to the 28-pin EDIP module. Ensure the ordering suffix aligns with the required access time specifications found in the official documentation.

Real Time Clock Selection Notes

Select based on required access time (85ns vs 100ns) and package style (EDIP vs PowerCap). Verify voltage range compatibility (4.5V to 5.5V) and operating temperature limits (0°C to +70°C). Consider the need for surface mount assembly if choosing the PowerCap variant, which requires separate ordering of the battery/crystal module.

Real Time Clock Part Context

The DS1643 series integrates memory and timekeeping functions into a single component. The DS1643-100 specifically denotes the 100ns access speed version within the 8K x 8 density family. It serves as a drop-in replacement for standard SRAMs while adding persistent timekeeping capabilities without external components.

Real Time Clock Replacement Considerations

Pin-for-pin compatible with other densities of the DS164XP timekeeping RAM family. When substituting, verify that the target device supports the same parallel interface timing and voltage levels. Note that different densities may have varying register maps for the clock functions.