Multichannel Remote/Local Temperature Sensors

Please check latest availability status for a specific part variant.


The MAX1668/MAX1805/MAX1989 are precise multichannel digital thermometers that report the temperature of all remote sensors and their own packages. The remote sensors are diode-connected transistors—typically low-cost, easily mounted 2N3904 NPN types—that replace conventional thermistors or thermocouples. Remote accuracy is ±3°C for multiple transistor manufacturers, with no calibration needed. The remote channels can also measure the die temperature of other ICs, such as microprocessors, that contain an on-chip, diode-connected transistor.

The 2-wire serial interface accepts standard system management bus (SMBus™) write byte, read byte, send byte, and receive byte commands to program the alarm thresholds and to read temperature data. The data format is 7 bits plus sign, with each bit corresponding to 1°C, in two's-complement format.

The MAX1668/MAX1805/MAX1989 are available in small, 16-pin QSOP surface-mount packages. The MAX1989 is also available in a 16-pin TSSOP.
MAX1668, MAX1805, MAX1989: Typical Operating Circuit MAX1668, MAX1805, MAX1989: Typical Operating Circuit Enlarge+

Key Features

  • Multichannel
    • 4 Remote, 1 Local (MAX1668/MAX1989)
    • 2 Remote, 1 Local (MAX1805)
  • No Calibration Required
  • SMBus 2-Wire Serial Interface
  • Programmable Under/Overtemperature Alarms
  • Supports SMBus Alert Response
  • Accuracy
    • ±2°C (+60°C to +100°C, Local)
    • ±3°C (-40°C to +125°C, Local)
    • ±3°C (+60°C to +100°C, Remote)
  • 3µA (typ) Standby Supply Current
  • 700µA (max) Supply Current
  • Small, 16-Pin QSOP/TSSOP Packages


  • Central Office Telecom Equipment
  • Desktop/Notebook Computers
  • Industrial Controls
  • LAN Servers
  • Multichip Modules
  • Test and Measurement Equipment
Product Reliability Reports: MAX1668.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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