The LM90 is an 11-bit digital temperature sensor with a 2-wire System Management Bus (SMBus) serial interface. The LM90 accurately measures its own temperature as well as the temperature of an external device, such as processor thermal diode or diode connected transistor such as the 2N3904. The temperature of any ASIC can be accurately determined using the LM90 as long as a dedicated diode (semiconductor junction) is available on the target die. The LM90 remote sensor accuracy of ±3°C is factory trimmed for the 1.008 typical non-ideality factor of the mobile Pentium III thermal diode. The LM90 has an Offset register to allow measuring other diodes without requiring continuous software management.

Activation of the ALERT output occurs when any temperature goes outside a preprogrammed window set by the HIGH and LOW temperature limit registers or exceeds the T_CRIT temperature limit. Activation of the T_CRIT_A occurs when any temperature exceeds the T_CRIT programmed limit. The LM90 is pin and register compatible with the LM86, Analog Devices ADM1032 and Maxim MAX6657/8.

• Accurately Senses Die Temperature of Remote ICs or Diode Junctions
• Offset Register Allows Sensing a Variety of Thermal Diodes Accurately
• On-board Local Temperature Sensing
• 10 Bit Plus Sign Remote Diode Temperature Data Format, 0.125°C Resolution
• Diode Fault Detection Circuitry
• T_CRIT_A Output Useful for System Shutdown (Open Diode does not Activate T_CRIT_A)
• ALERT Output Supports SMBus 2.0 Protocol
• SMBus 2.0 Compatible Interface, Supports TIMEOUT
• 8-pin VSSOP Package

Key Specifications

• Supply Voltage 3.0 to 3.6 V
• Supply Current 0.8 mA (Typ)
• Local Temp Accuracy (Includes Quantization Error)
  • TA=25°C to 125°C, ±4.0 °C (Max)
• Remote Diode Temp Accuracy (Includes Quantization Error)
  • TA=30°C to 50°C, TD=60°C to 100°C, ±3.0 °C (Max)
  • TA=0°C to 85°C, TD=25°C to 125°C, ±4.0 °C (Max)