1FEATURES

2? 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

APPLICATIONS

? Graphics Processor Thermal Management

? Computer Processor Thermal Management

? Electronic Test Equipment

? Office Electronics

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)

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.