Digital Thermometer and Thermostat

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The DS1721 digital thermometer and thermostat features ±1°C accuracy over a -10°C to +85°C range. Thermometer data is read out over a 2-wire serial bus in 2's complement format with 9 to 12 bits of resolution (user-programmable). The DS1721 features three address inputs, allowing users to multidrop up to eight DS1721 devices on one bus.

The DS1721 offers thermostatic functionality with over-temperature (TH) and under-temperature (TL) user-programmable trip-points stored in on-chip SRAM. The two trip-points provide programmable thermostat hysteresis: the thermostat output is asserted when the measured temperature exceeds TH and it remains active until the temperature falls below TL.

The DS1721 is available in 150mil 8-pin SO (DS1721S) and 8-pin µMAX/µSOP (DS1721U) packages. For applications requiring higher precision, the DS1631 provides ±0.5°C accuracy and is functionally compatible with the DS1721.
DS1721: Functional Block Diagram DS1721: Functional Block Diagram Enlarge+

Key Features

  • ±1°C accuracy from -10°C to +85°C
  • Measures temperatures from -55°C to +125°C (-67°F to +257°F)
  • 9- to 12-bit user-configurable resolution
  • Dedicated thermostatic logic output
  • Thermostatic settings are user-programmable
  • Data is transferred over 2-wire/SMBus interface
  • Three address inputs allow up to eight DS1721 to operate on one bus
  • 2.7V to 5.5V supply range
  • 150mil 8-pin SO (DS1721S) and 8-pin µMAX/µSOP (DS1721U) packages


  • Alarm Systems
  • Fibre Channel
  • Instrumentation
  • Networking
Part NumberSensor TypeInterfaceChannelsAccuracy
Parasite Pwr.Temp. Thresh.Temp. Resolution
Multi DroppableOper. Temp.
See Notes
DS1721 Local2-Wire/I2C/SMBusOne1NoProgrammable
Yes-55 to +125
SOIC (N)/8
$1.80 @1k
See All Temperature Sensors (112)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Tools & Models

  • DS1721 IBIS Model
  • CAD Symbols and Footprints

  • DS1721S
  • DS1721S+
  • DS1721S+T&R
  • DS1721S/T&R
  • DS1721S/T&R+W
  • DS1721U
  • DS1721U+
  • DS1721U+T&R
  • DS1721U/T&R
  • DS1721U/T&R+W
  • 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.

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