DS1642-70

Real Time Clock Overview

The DS1642-70 is a nonvolatile timekeeping RAM integrating a 2k x 8 static RAM and a real-time clock (RTC) in a single package. It features a standard JEDEC bytewide pinout with an access time of 70ns. The device operates on a 5.0V supply within a commercial temperature range of 0°C to +70°C. It includes an internal lithium energy source providing over 10 years of data retention without external power. The RTC registers are mapped to the top eight RAM locations, supporting BCD-coded timekeeping with leap year compensation.

Real Time Clock Feature Summary

• Integrated NV SRAM (2k x 8) and Real-Time Clock with 70ns access time
• Internal lithium battery provides >10 years data retention at 25°C
• BCD-coded calendar/clock with automatic leap year compensation valid to 2100
• Power-fail write protection circuitry prevents data corruption during voltage drops

Real Time Clock Applications

• Systems requiring persistent timekeeping and data storage in a compact footprint
• Replacement for ROM/EPROM sockets with added read/write nonvolatility
• Industrial controllers needing reliable clock functions without external components

Real Time Clock Procurement Notes

Verify component authenticity through authorized channels as this is a specialized legacy component. Confirm that the specific ordering suffix matches the required lead-free status (+) if applicable. Ensure the 24 EDIP package dimensions align with existing PCB footprints before procurement.

Real Time Clock Selection Notes

Select the DS1642-70 for applications requiring 70ns access speed; the DS1642-100 variant offers 100ns timing. Ensure the system VCC remains above 4.5V for normal operation, as the device enters data retention mode below the power-fail threshold. Verify that the 5V logic levels are compatible with the host microcontroller interface.

Real Time Clock Part Context

The DS1642 belongs to the Maxim Integrated DS16xx series of nonvolatile timekeeping RAMs. It combines the functionality of a standard SRAM with a full-function RTC, eliminating the need for separate clock chips and batteries. This integration simplifies board design while maintaining high reliability for time-sensitive data logging.

Real Time Clock Replacement Considerations

Direct pin-compatible replacements include other members of the DS1642 family such as the DS1642-100 for slower timing requirements. When substituting, ensure the new part supports the same 24 EDIP package and 5V operating voltage. Verify that any alternative maintains the integrated lithium battery feature if long-term data retention is critical.