Remote and Local Temperature Sensor with TruTherm Technology and SMBus Interface - LM99

LM99 (ACTIVE)

Remote and Local Temperature Sensor with TruTherm Technology and SMBus Interface

 

Description

The LM99 is an 11-bit remote diode temperature sensor with a 2-wire System Management Bus (SMBus) serial interface. The LM99 accurately measures: (1) its own temperature and (2) the temperature of a remote diode-connected transistor such as the 2N3904 or a thermal diode commonly found on Graphics Processor Units (GPU), Computer Processor Units (CPU or other ASICs. The LM99 remote diode temperature sensor shifts the temperature from the remote sensor down 16°C and operates on that shifted temperature:

  TACTUAL DIODE JUNCTION = TLM99 + 16°C

The local temperature reading requires no offset.

The LM99 has an Offset Register which provides a means for precise matching to various thermal diodes.

The LM99 and LM99-1 have the same functions but different SMBus slave addresses. This allows for one of each to be on the same bus at the same time.

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.

Features

  • Accurately Senses the Temperature of Remote Diodes
  • Offset Register Allows Use of a Variety of Thermal Diodes
  • On-board Local Temperature Sensing
  • 10 Bit Plus Sign Remote Diode Temperature Data Format, 0.125 °C Resolution
  • T_CRIT_A Output Useful for System Shutdown
  • ALERT Output Supports SMBus 2.0 Protocol
  • SMBus 2.0 Compatible Interface, Supports TIMEOUT
  • 8-Pin VSSOP Package

Key Specifications

  • Supply Voltage 3.0 V to 3.6 V
  • Supply Current 0.8 mA (typ)
  • Local Temp Accuracy
    (Includes Quantization error)
    • TA = 25°C to 125°C ±3.0°C (Max)
  • Remote Diode Temp Accuracy
    (Includes Quantization Error)
    • TA = 30°C to 50°C, TD = 120°C to 140°C ±1.0°C (Max)
    • TA = 0°C to 85°C, TD = 25°C to 140°C ±3.0°C (Max)

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Parametrics Compare all products in Remote / Multi-channel Temperature Sensors

 
Remote Channel
Local Sensor Accuracy (Max) (+/- C)
Remote Sensor Accuracy (Max) (+/- C)
Remote Diode Temp Range for Listed Accuracy (C)
Remote Temp Resolution (Max) (bits)
Remote Sensor Correction
Temp Resolution (Max) (bits)
Operating Temperature Range (C)
Supply Voltage (Min) (V)
Supply Voltage (Max) (V)
Supply Current (Typ) (uA)
Interface
Features
Rating
Package Group
Package Size: mm2:W x L (PKG)
LM99
1   
3   
1   
120 to 140   
11   
Offset Correction Register   
8   
0 to 85   
2.7   
5.5   
800   
I2C
SMBus   
One shot conversion control
Programmable Alert
Programmable conversion rate
Remote diode fault detection
Shutdown
Thermal diode input stage filtering   
Catalog   
VSSOP   
8VSSOP: 15 mm2: 4.9 x 3(VSSOP)