iButton 4Kb Memory Plus Time

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The iButton® 4Kb Memory Plus Time (DS1994) is a rugged read/write data carrier that acts as a localized database, easily accessible with minimal hardware. The nonvolatile memory and optional timekeeping capability offer a simple solution to storing and retrieving vital information pertaining to the object to which the iButton device is attached. Data is transferred serially through the 1-Wire® protocol that requires only a single data lead and a ground return.

The scratchpad is an additional page that acts as a buffer when writing to memory. Data is first written to the scratchpad where it can be read back. After the data has been verified, a copy scratchpad command transfers the data to memory. This process ensures data integrity when modifying the memory. A 48-bit serial number is factory lasered into each DS1994 to provide a guaranteed unique identity that allows for absolute traceability. The durable MicroCan package is highly resistant to environmental hazards such as dirt, moisture, and shock. Its compact, coin-shaped profile is self-aligning with mating receptacles, allowing the DS1994 to be easily used by human operators. Accessories permit the DS1994 to be mounted on almost any surface including plastic key fobs, photo-ID badges, and PC boards.

The DS1994 also includes time-keeping functions, a real-time clock/calendar, interval timer, cycle counter, and programmable interrupts, in addition to the nonvolatile memory. The internal clock can be programmed to deny memory access based on absolute time/date, total elapsed time, or the number of accesses. These features allow the DS1994 to be used to create a stopwatch, alarm clock, time and date stamp, logbook, hour meter, calendar, system power cycle timer, interval timer, and event scheduler.

Key Features

  • 4096 bits of Read/Write Nonvolatile Memory
  • 256-bit Scratchpad Ensures Integrity of Data Transfer
  • Memory Partitioned into 256-bit Pages for Packetizing Data
  • Data Integrity Assured with Strict Read/Write Protocols
  • Contains Real-Time Clock/Calendar in Binary Format
  • Interval Timer Can Automatically Accumulate Time When Power is Applied
  • Programmable Cycle Counter can Accumulate the Number of System Power-On/Off Cycles
  • Programmable Alarms Can Be Set to Generate Interrupts for Interval Timer, Real-Time Clock, and/or Cycle Counter
  • Write-Protect Feature Provides Tamperproof Time Data
  • Programmable Expiration Date That Limits Access to SRAM and Timekeeping
  • Clock Accuracy is Better Than ±2 Minutes/Month at 25°C
  • Operating Temperature Range from -40°C to +70°C
  • Over 10 Years of Data Retention

Technical Documents

App Note 4506 Alternatives to the DS1994L 4Kb Plus Time Memory iButton®
Reference Schematic 244 Advanced 1-Wire Network Driver
App Note 155 1-Wire Software Resource Guide Device Description

Quality and Environmental Data

Product Reliability Reports: DS1994.pdf 
Lead-Free Package Tin (Sn) Whisker Reports
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

Quality Management System >
Environmental Management System >


Related Resources

Type ID Title
Reference Circuit244Advanced 1-Wire Network Driver

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05/29/2020 - 05/31/2020, Detroit, MI
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