Document
LM95221
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SNIS134B – MAY 2004 – REVISED MARCH 2013
LM95221 Dual Remote Diode Digital Temperature Sensor with SMBus Interface
Check for Samples: LM95221
FEATURES
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•2 Accurately Senses Die Temperature of Remote ICs or Diode Junctions
• Remote Diode Fault Detection • On-board Local Temperature Sensing • Remote Temperature Readings
– 0.125°C LSb – 10-bits Plus Sign or 11-bits Programmable
Resolution – 11-bits Resolves Temperatures Above
127°C • Local Temperature Readings
– 0.25°C – 9-bits Plus Sign • Status Register Support • Programmable Conversion Rate Allows User Optimization of Power Consumption • Shutdown Mode One-shot Conversion Control • SMBus 2.0 Compatible Interface, Supports TIMEOUT • 8-pin VSSOP Package
KEY SPECIFICATIONS
• Local Temperature Accuracy – TA = 0°C to 85°C ± 3.0°C (max)
• Remote Diode Temperature Accuracy – TA = 30°C to 50°C, TD = 45°C to 85°C ±1.0 °C (Max) – TA = 0°C to 85°C, TD = 25°C to 140°C ±3.0°C (Max)
• Supply Voltage 3.0 V to 3.6 V • Supply Current 2 mA (Typ)
APPLICATIONS
• Processor/Computer System Thermal Management (e.g. Laptop, Desktop, Workstations, Server)
• Electronic Test Equipment
• Office Electronics
DESCRIPTION
The LM95221 is a dual remote diode temperature sensor in an 8-lead VSSOP 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.
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Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners.
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PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.
Copyright © 2004–2013, Texas Instruments Incorporated
LM95221
SNIS134B – MAY 2004 – REVISED MARCH 2013
Simplified Block Diagram
Local Diode Selector
D+
Remote
D-
Diode1 Selector
D+
Remote
D-
Diode2 Selector
3.0V-3.6V
Temperature Sensor Circuitry
LM95221
'-6 Converter 11-Bit or 10-Bit Plus Sign Remote
9-bit Plus Sign Local
Control Logic
Local Temperature
Registers
Remote 1 Temperature
Registers
Remote 2 Temperature
Registers
Configuration Register
Two-Wire Serial Interface
Status Registrer
Revision & Manufacturer ID Registers
SMBDAT SMBCLK
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Connection Diagram
D1+ 1
8 SMBCLK
D1- 2
7 SMBDAT
LM95221
D2+ 3
6
VDD
D2- 4
5 GND
Figure 1. VSSOP-8 TOP VIEW
Label D1+
D1− D2+
D2− GND VDD
SMBDAT SMBCLK
Pin # 1
2 3
4 5 6
7 8
PIN DESCRIPTIONS
Function
Typical Connection
Diode Current Source
To Diode Anode. Connected to remote discrete diodeconnected transistor junction or to the diode-connected transistor junction on a remote IC whose die temperature is being sensed. A 2.2 nF diode bypass capacitor is recommended to filter high frequency noise. Place the 2.2 nF capacitor between and as close as possible to the LM95221's D+ and D− pins. Make sure the traces to the 2.2 nF capacitor are matched. Ground this pin if this thermal diode is not used.
Diode Return Current Sink
To Diode Cathode. A 2.2 nF capacitor is recommended between D1+ and D1-. Ground this pin if this thermal diode is not used.
Diode Current Source
To Diode Anode. Connected to remote discrete diodeconnected transistor junction or to the diode-connected transistor junction on a remote IC whose die temperature is being sensed. A 2.2 nF diode bypass capacitor is recommended to filter high frequency noise. Place the 2.2 nF capacitor between and as close as possible to the LM95221's D+ and D− pins. Make sure the traces to the 2.2 nF capacitor are matched. Ground this pin if this thermal diode is not used.
Diode Return Current Sink
To Diode Cathode. A 2.2 nF capacitor is recommended between D2+ and D2-. Ground this pin if this thermal diode is not used.
Power Supply Ground
Ground
Positive Supply Voltage Input
DC Voltage from 3.0 V to 3.6 V. VDD s.