Programmable Digital Thermostat and Thermometer

Please check latest availability status for a specific part variant.


The DS1821 can function as a standalone thermostat with user-programmable trip-points or as 8-bit temperature sensor with a 1-Wire® digital interface. The thermostat trip-points are stored in nonvolatile memory, so DS1821 units can be programmed prior to system insertion for true standalone operation. The DS1821 has an operating temperature range of –55°C to +125°C and is accurate to ±1°C over a range of 0°C to +85°C. Communication with the DS1821 is accomplished through the open-drain DQ pin; this pin also serves as the thermostat output.
DS1821: Block Diagram DS1821: Block Diagram Enlarge+

Key Features

  • Requires no external components
  • Unique 1-Wire interface requires only one port pin for communication
  • Operates over a -55°C to +125°C (-67°F to +257°F) temperature range
  • Functions as a standalone thermostat with user-definable trip-points
  • Provides 8-bit (1°C resolution) centigrade temperature measurements
  • Accuracy is ±1°C over 0°C to +85°C range
  • Converts temperature to a digital word in 1 second (max)
  • Available in 3-pin TO92 and 8-pin SO packages
  • Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermally sensitive system


  • Consumer Products
  • Industrial Systems
  • Thermometers
  • Thermostatic Controls
Product Reliability Reports: DS1821.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

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.

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