DS1642-100

Real Time Clock Overview

The DS1642-100+ is a nonvolatile timekeeping RAM integrating a 2k x 8 SRAM and a real-time clock (RTC) in a single package. It operates on a 5.0V supply with access times of 100ns. The device features a standard JEDEC bytewide pinout, allowing it to substitute for ROM or EPROM sockets while providing read/write nonvolatility. The RTC registers reside in the eight uppermost RAM locations, storing year, month, date, day, hours, minutes, and seconds in BCD format. It includes an internal lithium energy source and power-fail control circuitry.

Real Time Clock Feature Summary

• Integrated NV SRAM and RTC with standard JEDEC 2k x 8 static RAM pinout
• Totally nonvolatile with over 10 years of operation without power
• BCD-coded timekeeping with leap year compensation valid up to 2100
• Power-fail write protection allows for ±10% VCC tolerance

Real Time Clock Applications

• Substitution in ROM, EPROM, and EEPROM sockets
• Systems requiring persistent timekeeping and data storage
• Industrial equipment needing battery-backed memory

Real Time Clock Procurement Notes

Verify component authenticity as this part may be discontinued. Confirm RoHS compliance status via the datasheet revision history. Check for lead-free packaging indicators (+ suffix). Ensure proper handling during wave-soldering to protect the internal lithium energy source from excessive heat exposure.

Real Time Clock Selection Notes

Select the DS1642-100+ for applications requiring 100ns access speed within the 0°C to +70°C temperature range. The -85 variant offers 85ns access. Ensure the system voltage remains within 4.5V to 5.5V to maintain write protection functionality. Verify that the application can accommodate the 24-pin EDIP package dimensions.

Real Time Clock Part Context

The DS1642 series combines nonvolatile memory with real-time clock functions. The -100 suffix denotes a 100ns access time version. It is part of the Maxim Integrated product line, now under Analog Devices. The device replaces traditional volatile SRAMs by adding timekeeping capabilities without changing the physical footprint or pin configuration.

Real Time Clock Replacement Considerations

The DS1642-85+ serves as a faster alternative with 85ns access time. Both variants share identical pinouts and functionality. No direct cross-model substitutes are documented in the provided datasheet.