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LM95231

www.ti.com

SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

LM95231 Precision Dual Remote Diode Temperature Sensor with SMBus Interface and

TruTherm™ Technology

Check for Samples: LM95231

FEATURES

KEY SPECIFICATIONS

• Accurately Senses Die Temperature of Remote

• Remote Temperature Accuracy ±0.75°C (max)

ICs or Diode Junctions

• Local Temperature Accuracy ±3.0°C (max)

• Uses TruTherm Technology for Precision

• Supply Voltage 3.0V to 3.6V

“Thermal Diode” Temperature Measurement

• Supply Current 402μA (typ)

• Thermal Diode Input Stage with Analog

Filtering

APPLICATIONS

• Thermal Diode Digital Filtering

• Processor/Computer System Thermal

• Intel Pentium 4 Processor on 90nm Process or

Management

2N3904 Non-ideality Selection

– e.g. Laptop, Desktop, Workstations, Server)

• Remote Diode Fault Detection

• Electronic Test Equipment

• On-board Local Temperature Sensing

• Office Electronics

• Remote Temperature Readings Without Digital

Filtering:

DESCRIPTION

– 0.125°C LSb

The LM95231 is a precision dual remote diode

temperature sensor (RDTS) that uses Texas

– 10-bits Plus Sign or 11-bits Programmable

Instruments' TruTherm technology. The 2-wire serial

Resolution

interface of the LM95231 is compatible with SMBus

– 11-bits Resolves Temperatures Above

2.0. The LM95231 can sense three temperature

127 °C

zones, it can measure the temperature of its own die

as well as two diode connected transistors. The

• Remote Temperature Readings with Digital

LM95231 includes digital filtering and an advanced

Filtering:

input stage that includes analog filtering and

– 0.03125°C LSb with Filtering

TruTherm technology that reduces processor-to-

– 12-bits Plus Sign or 13-bits Programmable

processor non-ideality spread. The diode connected

Resolution

transistors can be a “thermal diode” as found in Intel

and AMD processors or can simply be a diode

– 13-bits Resolves Temperatures Above

connected MMBT3904 transistor. TruTherm

127°C

technology allows accurate measurement of “thermal

• Local Temperature Readings:

diodes” found on small geometry processes, 90nm

– 0.25°C

and below. The LM95231 supports user selectable

thermal diode non-ideality of either a Pentium 4

– 9-bits Plus Sign

processor on 90nm process or 2N3904.

• Status Register Support

The LM95231 resolution format for remote

• Programmable Conversion Rate Allows User

temperature readings can be programmed to be 11-

Optimization of Power Consumption

bits signed or unsigned with the digital filtering

• Shutdown Mode One-shot Conversion Control

disabled. When the filtering is enabled the resolution

• SMBus 2.0 Compatible Interface, Supports

increases to 13-bits signed or unsigned. In the

unsigned mode the LM95231 remote diode readings

TIMEOUT

can resolve temperatures above 127°C. Local

• 8-pin VSSOP Package

temperature readings have a resolution of 9-bits plus

sign.

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.

2All trademarks are the property of their respective owners.

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.

Summary of content (29 pages)

PAGE 1
LM95231 www.ti.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com Connection Diagram D1+ 1 D1- 2 8 SMBCLK 7 D2+ 3 6 SMBDAT VDD D2- 4 5 GND LM95231 Figure 1. VSSOP-8 TOP VIEW Typical Application +3.3V Standby Pentium® 4 PROCESSOR C4** 100 pF 1 2 3 C5** 100 pF 4 D1+ SMBCLK D1- SMBDAT D2+ VDD D2- GND SMBCLK 7 SMBDAT 6 5 LM95231 Q1 MMBT3904 R2 1.3k R1 1.3k 8 C1* 100 pF C2 0.1 PF C3 10 PF + SMBus Master * Place close to LM95231 pins.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 Simplified Block Diagram 3.0V-3.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com Operating Ratings (1) (2) Operating Temperature Range 0°C to +125°C Electrical Characteristics Temperature Range TMIN≤TA≤TMAX LM95231BIMM, LM95231CIMM 0°C≤TA≤+85°C Supply Voltage Range (VDD) +3.0V to +3.6V (1) (2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is ensured to be functional, but do not ensure specific performance limits.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 Temperature-to-Digital Converter Characteristics (continued) Unless otherwise noted, these specifications apply for VDD=+3.0Vdc to 3.6Vdc. Boldface limits apply for TA = TJ = TMIN≤TA≤TMAX; all other limits TA= TJ=+25°C, unless otherwise noted. TJ is the junction temperature of the LM95231. TD is the junction temperature of the remote thermal diode.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com Logic Electrical Characteristics SMBus Digital Switching Characteristics Unless otherwise noted, these specifications apply for VDD=+3.0 Vdc to +3.6 Vdc, CL (load capacitance) on output lines = 80 pF. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = +25°C, unless otherwise noted. The switching characteristics of the LM95231 fully meet or exceed the published specifications of the SMBus version 2.0.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 Table 1. Parasitic components and ESD protection circuitry Pin # Circuit 1 A 2 A Pin ESD Protection Structure Circuits V+ PIN D2 D1 SNP PIN 3 D3 6.5V D1 A ESD CLAMP GND GND 4 A Circuit A Circuit C V+ 5 B ESD Clamp D2 160 k D3 80 k D1 6.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics Thermal Diode Capacitor or PCB Leakage Current Effect Remote Diode Temperature Reading Remote Temperature Reading Sensitivity to Thermal Diode Filter Capacitance Figure 3. Figure 4. Conversion Rate Effect on Average Power Supply Current 2.0 VDD = +3.3V AVERAGE I DD (mA) 1.75 TA = 25oC 1.5 1.25 1.0 0.75 0.5 0.25 0.0 10 100 1000 10000 CONVERSION TIME (ms) Figure 5.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 FUNCTIONAL DESCRIPTION The LM95231 is a digital sensor that can sense the temperature of 3 thermal zones using a sigma-delta analogto-digital converter. It can measure its local die temperature and the temperature of two external transistor junctions using a ΔVbe temperature sensing method. The LM95231 can support two external transistor types, a Pentium 4 processor on 90nm process thermal diode or a 2N3904 diode connected transistor.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com CONVERSION SEQUENCE In the power up default state the LM95231 takes maximum a 77.5 ms to convert the Local Temperature, Remote Temperature 1 and 2, and to update all of its registers. Only during the conversion process is the busy bit (D7) in the Status register (02h) high. These conversions are addressed in a round robin sequence. The conversion rate may be modified by the Conversion Rate bits found in the Configuration Register (03h).
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 Part Number A6 A5 A4 A3 A2 A1 A0 LM95231BIMM, LM95231CIMM 1 0 1 0 1 1 1 LM95231BIMM-1, LM95231CIMM-1 0 0 1 1 0 0 1 LM95231BIMM-2, LM95231CIMM-2 0 1 0 1 0 1 0 TEMPERATURE DATA FORMAT Temperature data can only be read from the Local and Remote Temperature registers .
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com Table 4. 13-bit, 2's complement (12-bit plus sign) Temperature Digital Output Binary Hex +125°C 0111 1101 0000 0000 7D00h +25°C 0001 1001 0000 0000 1900h +1°C 0000 0001 0000 0000 0100h +0.03125°C 0000 0000 0000 1000 0008h 0°C 0000 0000 0000 0000 0000h −0.03125°C 1111 1111 1111 1000 FFF8h −1°C 1111 1111 0000 0000 FF00h −25°C 1110 0111 0000 0000 E700h −55°C 1100 1001 0000 0000 C900h Table 5.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 SMBDAT OPEN-DRAIN OUTPUT The SMBDAT output is an open-drain output and does not have internal pull-ups. A “high” level will not be observed on this pin until pull-up current is provided by some external source, typically a pull-up resistor. Choice of resistor value depends on many system factors but, in general, the pull-up resistor should be as large as possible without effecting the SMBus desired data rate.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com 1 9 1 9 SMBCLK SMBDAT A6 A5 A4 A3 A2 D7 Ack by LM95231 A1 D6 A0 R/W Start by Master D5 D4 Frame 1 Serial Bus Address Byte D3 D2 SMBDAT (Continued) D0 Ack by LM95231 Frame 2 Command Byte 1 SMBCLK (Continued) D1 9 D7 D6 D5 D4 D3 D2 D1 D0 Ack by Stop LM95231 by Master Frame 3 Data Byte Figure 8.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 2. When SMBDAT is HIGH, have the master initiate an SMBus start. The LM95231 will respond properly to an SMBus start condition at any point during the communication. After the start the LM95231 will expect an SMBus Address address byte. ONE-SHOT CONVERSION The One-Shot register is used to initiate a single conversion and comparison cycle when the device is in standby mode, after which the device returns to standby.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com Bits Name Description 7 Busy When set to "1" the part is converting. 6-4 Reserved Reports "0" when read. 3 Remote 2 TruTherm Mode Enabled (R2TME) When set to "1" indicates that the TruTherm Mode has been activated for Remote diode 2. After being enabled TruTherm Mode will take at most one conversion cycle to be fully active.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 REMOTE DIODE FILTER CONTROL REGISTER D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 0 0 R2FE 0 R1FE Bits Name Description 7-3 Reserved Reports "0" when read. 2 Remote 2 Filter Enable (R2FE) 0: Filter Off 1: Noise Filter On 1 Reserved Reports "0" when read. 0 Remote 1 Filter Enable (R1FE) 0: Filter Off 1: Noise Filter On Power up default is 05h.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com LOCAL and REMOTE MSB and LSB TEMPERATURE REGISTERS Local Temperature MSB (Read Only Address 10h) 9-bit plus sign format: BIT D7 D6 D5 D4 D3 D2 D1 D0 Value SIGN 64 32 16 8 4 2 1 Temperature Data: LSb = 1°C. Local Temperature LSB (Read Only Address 20h) 9-bit plus sign format: BIT D7 D6 D5 D4 D3 D2 D1 D0 Value 0.5 0.25 0 0 0 0 0 0 Temperature Data: LSb = 0.25°C.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 DIE REVISION CODE REGISTER (Read Address FFh) The default value is A1h. This register will increment by 1 every time there is a revision to the die by Texas Instruments. Applications Hints The LM95231 can be applied easily in the same way as other integrated-circuit temperature sensors, and its remote diode sensing capability allows it to be used in new ways as well.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 'VBE = K x K qx T x ln www.ti.com IF2 IF1 (3) Solving Equation 3 for temperature yields: T= 'VBE x q IF2 K x k x ln IF1 (4) Equation 4 holds true when a diode connected transistor such as the MMBT3904 is used. When this “diode” equation is applied to an integrated diode such as a processor transistor with its collector tied to GND as shown in Figure 11 it will yield a wide non-ideality spread.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 TER = RPCB x 0.62°C/ : (9) Solving Equation 9 for RPCB equal to +0.264Ω and −0.088Ω results in the additional error due to the spread in the series resistance of +0.16°C to −0.05°C. The spread in error cannot be canceled out, as it would require measuring each individual thermal diode device. This is quite difficult and impractical in a large volume production environment.
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LM95231 SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 www.ti.com PCB LAYOUT FOR MINIMIZING NOISE Figure 12. Ideal Diode Trace Layout In a noisy environment, such as a processor mother board, layout considerations are very critical. Noise induced on traces running between the remote temperature diode sensor and the LM95231 can cause temperature conversion errors. Keep in mind that the signal level the LM95231 is trying to measure is in microvolts. The following guidelines should be followed: 1.
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LM95231 www.ti.com SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision D (March 2013) to Revision E • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM95231BIMM-1/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1 LM95231BIMM-2/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1 LM95231BIMM/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM95231BIMM-1/NOPB VSSOP DGK 8 1000 210.0 185.0 35.0 LM95231BIMM-2/NOPB VSSOP DGK 8 1000 210.0 185.0 35.0 LM95231BIMM/NOPB VSSOP DGK 8 1000 210.0 185.0 35.0 LM95231BIMMX-1/NOPB VSSOP DGK 8 3500 367.0 367.0 35.0 LM95231BIMMX-2/NOPB VSSOP DGK 8 3500 367.0 367.0 35.
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