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Maxim > Products > Sensors and Sensor Interface > MAX6646, MAX6647, MAX6649
Maxim > Products > Sensors and Sensor Interface > MAX6646, MAX6647, MAX6649

MAX6646, MAX6647, MAX6649

+145°C Precision SMBus-Compatible Remote/Local Sensors with Overtemperature Alarms

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Active: In Production.


The MAX6646/MAX6647/MAX6649 are precise, two-channel digital temperature sensors. The devices accurately measure the temperature of their own die and a remote PN junction, and report the temperature in digital form using a 2-wire serial interface. The remote PN junction is typically the emitter-base junction of a common-collector PNP on a CPU, FPGA, or ASIC.

The 2-wire serial interface accepts standard system management bus (SMBus) write byte, read byte, send byte, and receive byte commands to read the temperature data and to program the alarm thresholds. To enhance system reliability, the MAX6646/MAX6647/MAX6649 include an SMBus timeout. A fault queue prevents the active-low ALERT and active-low OVERT outputs from setting until a fault has been detected one, two, or three consecutive times (programmable).

The MAX6646/MAX6647/MAX6649 provide two system alarms: active-low ALERT and active-low OVERT. Active-low ALERT asserts when any of four temperature conditions are violated: local overtemperature, remote overtemperature, local undertemperature, or remote undertemperature. Active-low OVERT asserts when the temperature rises above the value in either of the two active-low OVERT limit registers. The active-low OVERT output can be used to activate a cooling fan, or to trigger a system shutdown.

Measurements can be done autonomously, at the programmed conversion rate, or in a single-shot mode. The adjustable conversion rate allows optimizing supply current and temperature update rate to match system needs.

Remote accuracy is ±1°C maximum error between +60°C and +145°C with no calibration needed. The MAX6646/MAX6647/MAX6649 operate from -55°C to +125°C, and measure temperatures between 0°C and +145°C. The MAX6646/MAX6647/MAX6649 are available in an 8-pin µMAX® package.

Data Sheet

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Key Features

  • Dual Channel: Measures Remote and Local Temperature
  • 0.125°C Resolution
  • High Accuracy ±1°C (max) from +60°C to +145°C (Remote), and ±2°C (max) from +60°C to +100°C (Local)
  • Measures High-Ideality Thermal Diodes Up to
    • +170°C (Apparent)
    • +145°C (Real)
  • Two Alarm Outputs: Active-Low ALERT and Active-Low OVERT
  • Programmable Under/Overtemperature Alarm Temperature Thresholds
  • Programmable Conversion Rate
  • SMBus-Compatible Interface
  • SMBus Timeout


  • Desktop Computers
  • Graphics Processors
  • Multichip Modules
  • Notebook Computers
  • Servers
  • Test and Measurement Equipment
  • Thin Clients
  • Workstations

Key Specifications:

Temperature Sensors
Part Number Sensor Type Alarm Output Functions Interface Remote Chan. Accuracy
Parasite Pwr. Temp. Thresh. Temp. Resolution
Oper. Temp.
See Notes
MAX6646  Remote
Dual Temperature Alarms
Remote & Local Sensor
2-Wire/I2C/SMBus Single 0.8 No Programmable 11 -55 to +125 $1.50 @1k
MAX6647  $1.50 @1k
MAX6649  $1.89 @1k
See All Temperature Sensors (111)

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.


MAX6646, MAX6647, MAX6649: Typical Operating Circuit
Typical Operating Circuit

More Information

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Document Ref.: 19-2540 Rev 4; 2012-08-06
This page last modified: 2012-08-06