LM95221| Datasheet

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LM95221 Dual Remote Diode Digital Temperature Sensor with SMBus Interface

May 2004

LM95221 Dual Remote Diode Digital Temperature Sensor with SMBus Interface
General Description
The LM95221 is a dual remote diode temperature sensor in an 8-lead MSOP package. The 2-wire serial interface of the LM95221 is compatible with SMBus 2.0. The LM95221 can sense three temperature zones, it can measure the temperature of its own die as well as two diode connected transistors. The diode connected transistors can be a thermal diode as found in Pentium and AMD processors or can simply be a diode connected MMBT3904 transistor. The LM95221 resolution format for remote temperature readings can be programmed to be 10-bits plus sign or 11-bits unsigned. In the unsigned mode the LM95221 remote diode readings can resolve temperatures above 127 C. Local temperature readings have a resolution of 9-bits plus sign. The temperature of any ASIC can be accurately determined using the LM95221 as long as a dedicated diode (semiconductor junction) is available on the target die. The LM95221 remote sensor accuracy of 1 C is factory trimmed for a series resistance of 2.7 ohms and 1.008 non-ideality factor. -- 11-b
its resolves temperatures above 127 C n Local temperature readings: -- 0.25 C -- 9-bits plus sign n Status register support n Programmable conversion rate allows user optimization of power consumption n Shutdown mode one-shot conversion control n SMBus 2.0 compatible interface, supports TIMEOUT n 8-pin MSOP package

Key Specifications
j Local Temperature Accuracy

TA=0 C to 85 C
j Remote Diode Temperature Accuracy

3.0 C (max) 1.0 C (max) 3.0 C (max)
3.0 V to 3.6 V 2 mA (typ)

TA=30 C to 50 C, TD=45 C to 85 C TA=0 C to 85 C, TD=25 C to 140 C
j Supply Voltage j Supply Current

Features
n Accurately senses die temperature of remote ICs or diode junctions n Remote diode fault detection n On-board local temperature sensing n Remote temperature readings: -- 0.125 C LSb -- 10-bits plus sign or 11-bits programmable resolution

Applications
n Processor/Computer System Thermal Management (e.g. Laptop, Desktop, Workstations, Server) n Electronic Test Equipment n Office Electronics

Simplified Block Diagram

20094301

PentiumTM is a trademark of Intel Corporation.

2004 National Semiconductor Corporation

DS200943

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