LM95231BIMM-1/NOPB - Texas Instruments

LM95231

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SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

LM95231 Precision Dual Remote Diode Temperature Sensor with SMBus Interface and

TruTherm™ Technology

Check for Samples: LM95231

1FEATURES KEY SPECIFICATIONS

2• 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.

1Please 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.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

SMBus

Master

* Place close to LM95231 pins.

** Optional may be required in noisy systems; place close to LM95231 pins.

MMBT3904

LM95231

D1+

D1-

D2+

D2- 5

VDD

SMBCLK

SMBDAT

GND C1*

100 pF

0.1 PF

SMBCLK

SMBDAT

C4**

100 pF

Pentium® 4

PROCESSOR

C5**

100 pF

+3.3V

Standby

1.3k

10 PF

LM95231 VDD

SMBCLK

SMBDAT

D1+

D1-

D2+

D2-

4 5

GND

LM95231

SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

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Connection Diagram

Figure 1. VSSOP-8

TOP VIEW

Typical Application

PIN DESCRIPTIONS

Label Pin # Function Typical Connection

D1+ 1 Diode Current Source To Diode Anode. Connected to remote discrete diode-

connected transistor junction or to the diode-connected

transistor junction on a remote IC whose die temperature is

being sensed. A capacitor is not required between D1+ and

D1-. A 100 pF capacitor between D1+ and D1−can be added

and may improve performance in noisy systems.

D1−2 Diode Return Current Sink To Diode Cathode. A capacitor is not required between D1+

and D1-. A 100 pF capacitor between D1+ and D1−can be

added and may improve performance in noisy systems.

D2+ 3 Diode Current Source To Diode Anode. Connected to remote discrete diode-

connected transistor junction or to the diode-connected

transistor junction on a remote IC whose die temperature is

being sensed. A capacitor is not required between D2+ and

D2-. A 100 pF capacitor between D2+ and D2−can be added

and may improve performance in noisy systems.

D2−4 Diode Return Current Sink To Diode Cathode. A capacitor is not required between D2+

and D2-. A 100 pF capacitor between D2+ and D2−can be

added and may improve performance in noisy systems.

GND 5 Power Supply Ground System low noise ground

VDD 6 Positive Supply Voltage Input DC Voltage from 3.0 V to 3.6 V. VDD should be bypassed with

a 0.1 µF capacitor in parallel with 100 pF. The 100 pF

capacitor should be placed as close as possible to the power

supply pin. Noise should be kept below 200 mVp-p, a 10 µF

capacitor may be required to achieve this.

SMBDAT 7 SMBus Bi-Directional Data Line, From and to Controller; may require an external pull-up resistor

Open-Drain Output

SMBCLK 8 SMBus Clock Input From Controller; may require an external pull-up resistor

Product Folder Links: LM95231

Local

Temperature

Registers

Remote 1

Temperature

Registers

SMBus Two Wire Serial Interface

Remote

Diode2 Selector

'-6Converter

11-Bit or 10-Bit Plus Sign Remote

9-bit Plus Sign Local

3.0V-3.6V

D+

D-

SMBDAT

SMBCLK

Remote 2

Temperature

Registers

Diode Filter

Control

Registers

Config

and

Status

Registrer

Revision &

Manufacturer

ID Registers

Remote

Diode1 Selector

D+

D-

Local

Diode Selector

TruThermTM

Temperature

Sensor

Circuitry

LM95231

Control

Logic

Diode Type

Selection

Diode

TruTherm

Control

LM95231

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SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

Simplified Block Diagram

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

Absolute Maximum Ratings(1)

Supply Voltage

Voltage at SMBDAT, SMBCLK −0.3 V to 6.0 V−0.5V to 6.0V

Voltage at Other Pins −0.3 V to (VDD + 0.3 V)

Input Current at All Pins(2) ±5 mA

Package Input Current(2) 30 mA

SMBDAT Output Sink Current 10 mA

Junction Tempeature(3) 125°C

Storage Temperature −65°C to +150°C

ESD Susceptibility(4) Human Body Model 2000 V

Machine Model 200 V

Soldering process must comply with Texas Instruments' reflow temperature profile specifications. Refer to http://www.ti.com/packaging/.(5)

(1) 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. For ensured specifications and test

conditions, see the Electrical Characteristics. The ensured specifications apply only for the test condition listed. Some performance

characteristics may degrade when the device is not operated under the listed test conditions. Operation of the device beyond the

Maximum Operating Ratings is not recommended.

(2) When the input voltage (VI) at any pin exceeds the power supplies (VI< GND or VI> VDD), the current at that pin should be limited to 5

mA. Parasitic components and or ESD protection circuitry are shown in Figure 2 and Table 1 for the LM95231's pins. Care should be

taken not to forward bias the parasitic diode, D1, present on pins: D1+, D2+, D1−, D2−. Doing so by more than 50 mV may corrupt the

temperature measurements.

(3) Thermal resistance junction-to-ambient when attached to a printed circuit board with 1oz. foil and no airflow:

— VSSOP-8 = 210°C/W

(4) Human body model, 100pF discharged through a 1.5kΩresistor. Machine model, 200pF discharged directly into each pin.

(5) Reflow temperature profiles are different for packages containing lead (Pb) than for those that do not.

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LM95231

SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

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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) 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. For ensured specifications and test

conditions, see the Electrical Characteristics. The ensured specifications apply only for the test condition listed. Some performance

characteristics may degrade when the device is not operated under the listed test conditions. Operation of the device beyond the

Maximum Operating Ratings is not recommended.

(2) Thermal resistance junction-to-ambient when attached to a printed circuit board with 1oz. foil and no airflow:

— VSSOP-8 = 210°C/W

Temperature-to-Digital Converter Characteristics

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. TJis the junction temperature of the LM95231. TDis the

junction temperature of the remote thermal diode.

PARAMETER TEST CONDITIONS Typical(LM9523 LM9523 UNIT

1) 1 1

BIMM CIMM

Limits(2) Limits(2)

Accuracy Using Local Diode TA= 0°C to +85°C(3)(4) ±1 ±3 ±3 °C (max)

Accuracy Using Remote Diode, see(5) TA= +20°C to +40°C; TD= Intel 90nm Thermal ±0.75 °C (max)

for Thermal Diode Processor Type. +45°C to +85°C Diode

TA= +20°C to +40°C; TD= MMBT3904 Thermal ±1.25 °C (max)

+45°C to +85°C Diode

TA= +20°C to +40°C; TD= Intel 90nm and ±1.25 °C (max)

+45°C to +85°C MMBT3904 Thermal

Diodes

TA= +0°C to +85°C; TD= Intel 90nm and ±2.5 ±2.5 °C (max)

+25°C to +140°C MMBT3904 Thermal

Diodes

Remote Diode Measurement Resolution 10+sign/ Bits

with filtering turned off 11

0.125 °C

Remote Diode Measurement Resolution 12+sign/ Bits

with digital filtering turned on 13

0.03125 °C

Local Diode Measurement Resolution 9+sign Bits

0.25 °C

Conversion Time of All Temperatures at See(6) TruTherm Mode Disabled 75.8 83.9 83.9 ms

the Fastest Setting (max)

TruTherm Mode enabled 79.2 87.7 87.7 ms

(max)

Average Quiescent Current(7) SMBus Inactive, 1 Hz conversion rate 402 545 545 µA (max)

Shutdown 272 µA

D−Source Voltage 0.4 V

(1) Typicals are at TA= 25°C and represent most likely parametric norm at time of product characterization. The typical specifications are

not ensured.

(2) Limits are specified to AOQL (Average Outgoing Quality Level).

(3) Local temperature accuracy does not include the effects of self-heating. The rise in temperature due to self-heating is the product of the

internal power dissipation of the LM95231 and the thermal resistance. See Note 2 of the Operating Ratings table for the thermal

resistance to be used in the self-heating calculation.

(4) Thermal resistance junction-to-ambient when attached to a printed circuit board with 1oz. foil and no airflow:

— VSSOP-8 = 210°C/W

(5) The accuracy of the LM95231 is ensured when using the thermal diode of Pentium 4 processor on 90nm process or an MMBT3904 type

transistor, as selected in the Remote Diode Model Select register.

(6) This specification is provided only to indicate how often temperature data is updated. The LM95231 can be read at any time without

regard to conversion state (and will yield last conversion result).

(7) Quiescent current will not increase substantially when the SMBus is active.

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LM95231

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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. TJis the junction temperature of the LM95231. TDis the

junction temperature of the remote thermal diode.

PARAMETER TEST CONDITIONS Typical(LM9523 LM9523 UNIT

1) 1 1

BIMM CIMM

Limits(2) Limits(2)

Diode Source Current Ratio 16

Diode Source Current (VD+ −VD−) = + 0.65V; 176 300 300 µA (max)

high-level 100 100 µA (min)

Low-level 11 µA

Power-On Reset Threshold Measure on VDD input, falling edge 2.7 2.7 V (max)

1.8 1.8 V (min)

Logic Electrical Characteristics

Digital DC Characteristics

Unless otherwise noted, these specifications apply for VDD=+3.0 to 3.6 Vdc. Boldface limits apply for TA= TJ= TMIN to

TMAX;all other limits TA= TJ=+25°C, unless otherwise noted.

Symbol Parameter Conditions Typical(1) Limits(2) Units

(Limit)

SMBDAT, SMBCLK INPUTS

VIN(1) Logical “1” Input Voltage 2.1 V (min)

VIN(0) Logical “0”Input Voltage 0.8 V (max)

VIN(HYST) SMBDAT and SMBCLK Digital Input 400 mV

Hysteresis

IIN(1) Logical “1” Input Current VIN = VDD 0.005 ±10 µA (max)

IIN(0) Logical “0” Input Current VIN = 0 V −0.005 ±10 µA (max)

CIN Input Capacitance 5 pF

SMBDAT OUTPUT

IOH High Level Output Current VOH = VDD 10 µA (max)

VOL SMBus Low Level Output Voltage IOL = 4mA 0.4 V (max)

IOL = 6mA 0.6

(1) Typicals are at TA= 25°C and represent most likely parametric norm at time of product characterization. The typical specifications are

not ensured.

(2) Limits are specified to AOQL (Average Outgoing Quality Level).

Product Folder Links: LM95231

VIH

VIL

SMBCLK

VIH

VIL

SMBDAT

tBUF tHD;STA

tLOW

tHD;DAT tHIGH

tSU;DAT tSU;STA tSU;STO

LM95231

SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

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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. The

following parameters are the timing relationships between SMBCLK and SMBDAT signals related to the LM95231. They

adhere to but are not necessarily the SMBus bus specifications.

Symbol Parameter Conditions Typical(1) Limits(2) Units

(Limit)

fSMB SMBus Clock Frequency 100 kHz (max)

10 kHz (min)

tLOW SMBus Clock Low Time from VIN(0)max to VIN(0)max 4.7 µs (min)

25 ms (max)

tHIGH SMBus Clock High Time from VIN(1)min to VIN(1)min 4.0 µs (min)

tR,SMB SMBus Rise Time See(3) 1 µs (max)

tF,SMB SMBus Fall Time See(4) 0.3 µs (max)

tOF Output Fall Time CL= 400pF, 250 ns (max)

IO= 3mA(4)

tTIMEOUT SMBDAT and SMBCLK Time Low for Reset of 25 ms (min)

Serial Interface(5) 35 ms (max)

tSU;DAT Data In Setup Time to SMBCLK High 250 ns (min)

tHD;DAT Data Out Stable after SMBCLK Low 300 ns (min)

1075 ns (max)

tHD;STA Start Condition SMBDAT Low to SMBCLK Low 100 ns (min)

(Start condition hold before the first clock falling

edge)

tSU;STO Stop Condition SMBCLK High to SMBDAT Low 100 ns (min)

(Stop Condition Setup)

tSU;STA SMBus Repeated Start-Condition Setup Time, 0.6 µs (min)

SMBCLK High to SMBDAT Low

tBUF SMBus Free Time Between Stop and Start 1.3 µs (min)

Conditions

(1) Typicals are at TA= 25°C and represent most likely parametric norm at time of product characterization. The typical specifications are

not ensured.

(2) Limits are specified to AOQL (Average Outgoing Quality Level).

(3) The output rise time is measured from (VIN(0)max + 0.15V) to (VIN(1)min −0.15V).

(4) The output fall time is measured from (VIN(1)min - 0.15V) to (VIN(1)min + 0.15V).

(5) Holding the SMBDAT and/or SMBCLK lines Low for a time interval greater than tTIMEOUT will reset the LM95231's SMBus state machine,

therefore setting SMBDAT and SMBCLK pins to a high impedance state.

Figure 2. SMBus Communication

Product Folder Links: LM95231

V+

GND

ESD

Clamp 6.5V

160 k

80 k

GND

V+

6.5V

D3 ESD

CLAMP

SNP

GND

LM95231

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SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

Table 1. Parasitic components and ESD protection circuitry

Pin # Circuit Pin ESD Protection Structure Circuits

1 A

2 A

3 A

4 A Circuit A Circuit C

5 B

6 B Circuit B

7 C

8 C

Product Folder Links: LM95231

10 100 1000 10000

CONVERSION TIME (ms)

0.0

0.25

0.5

0.75

1.0

1.25

1.5

1.75

2.0

AVERAGE IDD (mA)

VDD = +3.3V

TA= 25oC

LM95231

SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

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Typical Performance Characteristics

Thermal Diode Capacitor or PCB Leakage Current Effect Remote Temperature Reading Sensitivity to Thermal Diode

Remote Diode Temperature Reading Filter Capacitance

Figure 3. Figure 4.

Conversion Rate Effect on Average Power Supply Current

Figure 5.

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LM95231

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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 analog-

to-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. The transistor

type is register programmable and does not require software intervention after initialization. The LM95231 has an

advanced input stage using Texas Instruments' TruTherm technology that reduces the spread in non-ideality

found in Pentium 4 processors on 90nm process. Internal analog filtering has been included in the thermal diode

input stage thus minimizing the need for external thermal diode filter capacitors. In addition a digital filter has

been added. These noise immunity improvements in the analog input stage along with the digital filtering will

allow longer trace tracks or cabling to the thermal diode than previous thermal diode sensor devices.

The 2-wire serial interface, of the LM95231, is compatible with SMBus 2.0 and I2C. Please see the SMBus 2.0

specification for a detailed description of the differences between the I2C bus and SMBus.

The temperature conversion rate is programmable to allow the user to optimize the current consumption of the

LM95231 to the system requirements. The LM95231 can be placed in shutdown to minimize power consumption

when temperature data is not required. While in shutdown, a 1-shot conversion mode allows system control of

the conversion rate for ultimate flexibility.

The remote diode temperature resolution is variable and depends on whether the digital filter is activated. When

the digital filter is active the resolution is thirteen bits and is programmable to 13-bits unsigned or 12-bits plus

sign, with a least-significant-bit (LSb) weight for both resolutions of 0.03125°C. When the digital filter is inactive

the resolution is eleven bits and is programmable to 11-bits unsigned or 10-bits plus sign, with a least-significant-

bit (LSb) weight for both resolutions of 0.125°C. The unsigned resolution allows the remote diodes to sense

temperatures above 127°C. Local temperature resolution is not programmable and is always 9-bits plus sign and

has a 0.25°C LSb.

The LM95231 remote diode temperature accuracy will be trimmed for the thermal diode of a Pentium 4 processor

on 90nm process or a 2N3904 transistor and the accuracy will be ensured only when using either of these diodes

when selected appropriately. TruTherm mode should be enabled when measuring a Pentium 4 processor on

90nm process and disabled when measuring a 2N3904 transistor. Enabling TruTherm mode with a 2N3904

transistor connected may produce unexpected temperature readings.

Diode fault detection circuitry in the LM95231 can detect the presence of a remote diode: whether D+ is shorted

to VDD, D- or ground, or whether D+ is floating.

The LM95231 register set has an 8-bit data structure and includes:

1. Most-Significant-Byte (MSB) Local Temperature Register

2. Least-Significant-Byte (LSB) Local Temperature Register

3. MSB Remote Temperature 1 Register

4. LSB Remote Temperature 1 Register

5. MSB Remote Temperature 2 Register

6. LSB Remote Temperature 2 Register

7. Status Register: busy, diode fault

8. Configuration Register: resolution control, conversion rate control, standby control

9. Remote Diode Filter Setting

10. Remote Diode Model Select

11. Remote Diode TruTherm Mode Control

12. 1-shot Register

13. Manufacturer ID

14. Revision ID

Product Folder Links: LM95231

10 100 1000 10000

CONVERSION TIME (ms)

0.0

0.25

0.5

0.75

1.0

1.25

1.5

1.75

2.0

AVERAGE IDD (mA)

VDD = +3.3V

TA= 25oC

LM95231

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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). When the conversion

rate is modified a delay is inserted between conversions, the actual maximum conversion time remains at 87.7

ms. Different conversion rates will cause the LM95231 to draw different amounts of supply current as shown in

Figure 6.

Figure 6. Conversion Rate Effect on Power Supply Current

POWER-ON-DEFAULT STATES

LM95231 always powers up to these known default states. The LM95231 remains in these states until after the

first conversion.

1. Command Register set to 00h

2. Local Temperature set to 0°C until the end of the first conversion

3. Remote Diode Temperature set to 0°C until the end of the first conversion

4. Remote Diode digital filters are on.

5. Remote Diode 1 model is set to Pentium 4 processor on 90nm process with TruTherm mode enabled.

Remote Diode 2 model is set to 2N3904 with TruTherm mode disabled.

6. Status Register depends on state of thermal diode inputs

7. Configuration register set to 00h; continuous conversion, typical time = 85.8 ms when TruTherm Mode is

enabled for Remote 1 only

SMBus INTERFACE

The LM95231 operates as a slave on the SMBus, so the SMBCLK line is an input and the SMBDAT line is

bidirectional. The LM95231 never drives the SMBCLK line and it does not support clock stretching. According to

SMBus specifications, the LM95231 has a 7-bit slave address. All bits A6 through A0 are internally programmed

and can not be changed by software or hardware. The SMBus slave address is dependent on the LM95231 part

number ordered:

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LM95231

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SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

Part Number A6 A5 A4 A3 A2 A1 A0

LM95231BIMM, 1 0 1 0 1 1 1

LM95231CIMM

LM95231BIMM-1, 0 0 1 1 0 0 1

LM95231CIMM-1

LM95231BIMM-2, 0 1 0 1 0 1 0

LM95231CIMM-2

TEMPERATURE DATA FORMAT

Temperature data can only be read from the Local and Remote Temperature registers .

Remote temperature data with the digital filter off is represented by an 11-bit, two's complement word or

unsigned binary word with an LSb (Least Significant Bit) equal to 0.125°C. The data format is a left justified 16-bit

word available in two 8-bit registers. Unused bits will always report "0".

Table 2. 11-bit, 2's complement (10-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

+0.125°C 0000 0000 0010 0000 0020h

0°C 0000 0000 0000 0000 0000h

−0.125°C 1111 1111 1110 0000 FFE0h

−1°C 1111 1111 0000 0000 FF00h

−25°C 1110 0111 0000 0000 E700h

−55°C 1100 1001 0000 0000 C900h

Table 3. 11-bit, unsigned binary

Temperature Digital Output

Binary Hex

+255.875°C 1111 1111 1110 0000 FFE0h

+255°C 1111 1111 0000 0000 FF00h

+201°C 1100 1001 0000 0000 C900h

+125°C 0111 1101 0000 0000 7D00h

+25°C 0001 1001 0000 0000 1900h

+1°C 0000 0001 0000 0000 0100h

+0.125°C 0000 0000 0010 0000 0020h

0°C 0000 0000 0000 0000 0000h

Remote temperature data with the digital filter on is represented by a 13-bit, two's complement word or unsigned

binary word with an LSb (Least Significant Bit) equal to 0.03125°C (1/32°C). The data format is a left justified 16-

bit word available in two 8-bit registers. Unused bits will always report "0".

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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. 13-bit, unsigned binary

Temperature Digital Output

Binary Hex

+255.875°C 1111 1111 1110 0000 FFE0h

+255°C 1111 1111 0000 0000 FF00h

+201°C 1100 1001 0000 0000 C900h

+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

Local Temperature data is represented by a 10-bit, two's complement word with an LSb (Least Significant Bit)

equal to 0.25°C. The data format is a left justified 16-bit word available in two 8-bit registers. Unused bits will

always report "0". Local temperature readings greater than +127.875°C are clamped to +127.875°C, they will not

roll-over to negative temperature readings.

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

+0.25°C 0000 0000 0100 0000 0040h

0°C 0000 0000 0000 0000 0000h

−0.25°C 1111 1111 1100 0000 FFC0h

−1°C 1111 1111 0000 0000 FF00h

−25°C 1110 0111 0000 0000 E700h

−55°C 1100 1001 0000 0000 C900h

Product Folder Links: LM95231

D7 D6 D5 D4 D3 D2 D1 D0

1 9 1 9

Ack

LM95231

Start by

Master

R/W

Frame 1

Serial Bus Address Byte

Frame 2

Command Byte

Ack by

LM95231

SMBCLK

SMBDAT A5 A3 A2 A0A6 A4 A1

Stop

Master

LM95231

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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. This will minimize any internal temperature reading

errors due to internal heating of the LM95231. The maximum resistance of the pull-up to provide a 2.1V high

level, based on LM95231 specification for High Level Output Current with the supply voltage at 3.0V, is 82kΩ

(5%) or 88.7kΩ(1%).

1.6 DIODE FAULT DETECTION

The LM95231 is equipped with operational circuitry designed to detect fault conditions concerning the remote

diodes. In the event that the D+ pin is detected as shorted to GND, D−, VDD or D+ is floating, the Remote

Temperature reading is –128.000 °C if signed format is selected and +255.875 if unsigned format is selected. In

addition, the appropriate status register bits RD1M or RD2M (D1 or D0) are set. When TruTherm mode is active

the condition of diode short of D+ to D−will not be detected. Connecting a 2N3904 transistor with TruTherm

mode active may cause a detection of a diode fault.

1.7 COMMUNICATING with the LM95231

The data registers in the LM95231 are selected by the Command Register. At power-up the Command Register

is set to “00”, the location for the Read Local Temperature Register. The Command Register latches the last

location it was set to. Each data register in the LM95231 falls into one of four types of user accessibility:

1. Read only

2. Write only

3. Write/Read same address

4. Write/Read different address

AWrite to the LM95231 will always include the address byte and the command byte. A write to any register

requires one data byte.

Reading the LM95231 can take place either of two ways:

1. If the location latched in the Command Register is correct (most of the time it is expected that the Command

read from the LM95231), then the read can simply consist of an address byte, followed by retrieving the data

byte.

2. If the Command Register needs to be set, then an address byte, command byte, repeat start, and another

address byte will accomplish a read.

The data byte has the most significant bit first. At the end of a read, the LM95231 can accept either acknowledge

or No Acknowledge from the Master (No Acknowledge is typically used as a signal for the slave that the Master

has read its last byte). When retrieving all 11 bits from a previous remote diode temperature measurement, the

master must insure that all 11 bits are from the same temperature conversion. This may be achieved by reading

the MSB register first. The LSB will be locked after the MSB is read. The LSB will be unlocked after being read. If

the user reads MSBs consecutively, each time the MSB is read, the LSB associated with that temperature will be

locked in and override the previous LSB value locked-in.

Figure 7. Serial Bus Write to the Internal Command Register

Product Folder Links: LM95231

D7 D6 D5 D4 D3 D2 D1 D0

1 9 1 9

Ack

LM95231

Start by

Master

Repeat

Start by

Master

R/W

Frame 1

Serial Bus Address Byte

Frame 2

Command Byte

Ack

LM95231

D7 D6 D5 D4 D3 D2 D1 D0

1 9 1 9

Ack

LM95231

R/W

Frame 3

Serial Bus Address Byte

Frame 4

Data Byte from the LM95231

No Ack

Master

Stop

Master

SMBCLK

SMBDAT

SMBCLK

(Continued)

SMBDAT

(Continued)

A5 A3 A2 A0A6 A4 A1

D7 D6 D5 D4 D3 D2 D1 D0

1 9 1 9

Ack

LM95231

Start by

Master

R/W

Frame 1

Serial Bus Address Byte

Frame 2

Data Byte from the LM95231

NoAck

Master

SMBCLK

SMBDAT

Stop

Master

A5 A3 A2 A0

A6 A4 A1

D7 D6 D5 D4 D3 D2 D1 D0

1 9 1 9

Ack

LM95231

Start by

Master

R/W

Frame 1

Serial Bus Address Byte

Frame 2

Command Byte

Ack

LM95231

D7 D6 D5 D4 D3 D2 D1 D0

1 9

Frame 3

Data Byte

Ack by

LM95231

Stop

Master

SMBCLK

SMBDAT

SMBCLK

(Continued)

SMBDAT

(Continued)

A5 A3 A2 A0A6 A4 A1

LM95231

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Figure 8. Serial Bus Write to the internal Command Register followed by a Data Byte

Figure 9. Serial Bus byte Read from a Register with the internal Command Register preset to desired

value.

(d) Serial Bus Write followed by a Repeat Start and Immediate Read

Figure 10. SMBus Timing Diagrams for Access of Data

SERIAL INTERFACE RESET

In the event that the SMBus Master is RESET while the LM95231 is transmitting on the SMBDAT line, the

LM95231 must be returned to a known state in the communication protocol. This may be done in one of two

ways:

1. When SMBDAT is LOW, the LM95231 SMBus state machine resets to the SMBus idle state if either

SMBDAT or SMBCLK are held low for more than 35ms (tTIMEOUT). Note that according to SMBus

specification 2.0 all devices are to timeout when either the SMBCLK or SMBDAT lines are held low for 25-

35ms. Therefore, to insure a timeout of all devices on the bus the SMBCLK or SMBDAT lines must be held

low for at least 35ms.

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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. This is not a data register and it is the write operation that

causes the one-shot conversion. The data written to this address is irrelevant and is not stored. A zero will

always be read from this register.

LM95231 Registers

Command register selects which registers will be read from or written to. Data for this register should be

transmitted during the Command Byte of the SMBus write communication.

P7 P6 P5 P4 P3 P2 P1 P0

Command

P0-P7: Command

Table 6. Register Summary

Name Command Power-On Read/Write # of used bits Comments

(Hex) Default Value

(Hex)

Status Register 02h - RO 5 4 status bits and 1 busy bit

Configuration Register 03h 00h R/W 5 Includes conversion rate control

Remote Diode Filter Control 06h 05h R/W 2 Controls thermal diode filter

setting

Remote Diode Model Type 30h 01h R/W 2 Selects the 2N3904 or Pentium

Select 4 processor on 90nm process

thermal diode model

Remote Diode TruTherm Mode 07h 01h 8 Enables or disables TruTherm

Control technology for Remote Diode

measurements

1-shot 0Fh - WO - Activates one conversion for all

3 channels if the chip is in

standby mode (i.e. RUN/STOP

bit = 1). Data transmitted by the

host is ignored by the LM95231.

Local Temperature MSB 10h - RO 8

Remote Temperature 1 MSB 11h - RO 8

Remote Temperature 2 MSB 12h - RO 8

Local Temperature LSB 20h - RO 2 All unused bits will report zero

Remote Temperature 1 LSB 21h - RO 3/5 All unused bits will report zero

Remote Temperature 2 LSB 22h - RO 3/5 All unused bits will report zero

Manufacturer ID FEh 01h RO

Revision ID FFh A1h RO

STATUS REGISTER

D7 D6 D5 D4 D3 D2 D1 D0

Busy Reserved R2TME R1TME RD2M RD1M

000

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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 When set to "1" indicates that the TruTherm Mode has been activated for

(R2TME) Remote diode 2. After being enabled TruTherm Mode will take at most one

conversion cycle to be fully active.

2 Remote 1 TruTherm Mode Enabled When set to "1" indicates that the TruTherm Mode has been activated for

(R2TME) Remote diode 1. After being enabled TruTherm Mode will take at most one

conversion cycle to be fully active.

1 Remote Diode 2 Missing (RD2M) When set to "1" Remote Diode 2 is missing. (i.e. D2+ shorted to VDD, Ground

or D2-, or D2+ is floating). Temperature Reading is FFE0h which converts to

255.875 °C if unsigned format is selected or 8000h which converts to

–128.000 °C if signed format is selected. Note, connecting a 2N3904 transistor

to Remote 2 inputs with TruTherm mode active may also cause this bit to be

set.

0 Remote Diode 1 Missing (RD1M) When set to "1" Remote Diode 1 is missing. (i.e. D1+ shorted to VDD, Ground

or D1-, or D1+ is floating). Temperature Reading is FFE0h which converts to

255.875 °C if unsigned format is selected or 8000h which converts to

–128.000 °C if signed format is selected. Note, connecting a 2N3904 transistor

to Remote 1 inputs with TruTherm mode active may also cause this bit to be

set.

CONFIGURATION REGISTER

D7 D6 D5 D4 D3 D2 D1 D0

0 RUN/STOP CR1 CR0 0 R2DF R1DF 0

Bits Name Description

7 Reserved Reports "0" when read.

6 RUN/STOP Logic 1 disables the conversion and puts the part in standby mode.

Conversion can be activated by writing to one-shot register.

5-4 Conversion Rate (CR1:CR0) 00: continuous mode 75.8 ms, 13.2 Hz (typ), when diode mode is selected for

both remote channels; 77.5 ms, 12.9 Hz (typ), when TruTherm Mode is

enabled for one remote channel.

01: converts every 182 ms, 5.5 Hz (typ)

10: converts every 1 second, 1 Hz (typ)

11: converts every 2.7 seconds, 0.37 Hz (typ)

Note: typically a remote diode conversion takes 30 ms with diode mode is

selected; when the TruTherm Mode is selected a conversion takes an

additional 1.7 ms; a local conversion takes 15.8 ms.

3 Reserved Reports "0" when read.

2 Remote 2 Data Format (R2DF) Logic 0: unsigned Temperature format (0 °C to +255.875 °C)

Logic 1: signed Temperature format (-128 °C to +127.875 °C)

1 Remote 1 Data Format (R1DF) Logic 0: unsigned Temperature format (0 °C to +255.875 °C)

Logic 1: signed Temperature format (-128 °C to +127.875 °C)

0 Reserved Reports "0" when read.

Power up default is with all bits “0” (zero)

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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.

REMOTE DIODE MODEL TYPE SELECT REGISTER

D7 D6 D5 D4 D3 D2 D1 D0

0 0 0 0 0 R2MS 0 R1MS

Bits Name Description

7-3 Reserved Reports "0" when read.

2 Remote Diode 2 Model Select (R2MS) 0: 2N3904 model (make sure TruTherm mode is disabled)

1: Pentium 4 processor on 90nm process model (make sure TruTherm mode

is enabled)

Power up default is 0.

1 Reserved Reports "0" when read.

0 Remote Diode 1 Model Select (R1MS) 0: 2N3904 model (make sure TruTherm mode is disabled)

1: Pentium 4 processor on 90nm process model (make sure TruTherm mode

is enabled)

Power up default is 1.

Power up default is 01h.

REMOTE TruTherm MODE CONTROL

D7 D6 D5 D4 D3 D2 D1 D0

Reserved R2M2 R2M1 R2M0 Reserved R1M2 R1M1 R1M0

Bits Description

7 Reserved Must be left at 0.

6-4 R2M2:R2M0 000: Remote 2 TruTherm Mode disabled; used when measuring MMBT3904

transistors

001: Remote 2 TruTherm Mode enabled; used when measuring Processors

111: Remote 2 TruTherm Mode enabled; used when measuring Processors

Note, all other codes provide unspecified results and should not be used.

3 Reserved Must be left at 0.

2-0 R1M2:R1M0 000: Remote 1 TruTherm Mode disabled; used when measuring MMBT3904

transistors

001: Remote 1 TruTherm Mode enabled; used when measuring Processors

111: Remote 1 TruTherm Mode enabled; used when measuring Processors

Note, all other codes provide unspecified results and should not be used.

Power up default is 01h.

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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.

Remote Temperature MSB

(Read Only Address 11h, 12h) 10 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.

(Read Only Address 11h, 12h) 11-bit unsigned format:

BIT D7 D6 D5 D4 D3 D2 D1 D0

Value 128 64 32 16 8 4 2 1

Temperature Data: LSb = 1°C.

Remote Temperature LSB

12-bit plus sign or 13-bit unsigned binary formats with filter on:

BIT D7 D6 D5 D4 D3 D2 D1 D0

Value 0.5 0.25 0.125 0 0 0 0 0

Temperature Data: LSb = 0.125°C or 1/8°C.

12-bit plus sign or 13-bit unsigned binary formats with filter on:

BIT D7 D6 D5 D4 D3 D2 D1 D0

Value 0.5 0.25 0.125 0.0625 0.03125 0 0 0

Temperature Data: LSb = 0.03125°C or 1/32°C.

For data synchronization purposes, the MSB register should be read first if the user wants to read both MSB and

LSB registers. The LSB will be locked after the MSB is read. The LSB will be unlocked after being read. If the

user reads MSBs consecutively, each time the MSB is read, the LSB associated with that temperature will be

locked in and override the previous LSB value locked-in.

MANUFACTURERS ID REGISTER

(Read Address FEh) The default value is 01h.

Product Folder Links: LM95231

IF = IS e

Vbe

KVt

Vt = k T

IF = IS x e -1

VBE

Kx Vt

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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. It can be soldered to a printed circuit

board, and because the path of best thermal conductivity is between the die and the pins, its temperature will

effectively be that of the printed circuit board lands and traces soldered to the LM95231's pins. This presumes

that the ambient air temperature is almost the same as the surface temperature of the printed circuit board; if the

air temperature is much higher or lower than the surface temperature, the actual temperature of the LM95231 die

will be at an intermediate temperature between the surface and air temperatures. Again, the primary thermal

conduction path is through the leads, so the circuit board temperature will contribute to the die temperature much

more strongly than will the air temperature.

To measure temperature external to the LM95231's die, use a remote diode. This diode can be located on the

die of a target IC, allowing measurement of the IC's temperature, independent of the LM95231's temperature. A

discrete diode can also be used to sense the temperature of external objects or ambient air. Remember that a

discrete diode's temperature will be affected, and often dominated, by the temperature of its leads. Most silicon

diodes do not lend themselves well to this application. It is recommended that an MMBT3904 transistor base

emitter junction be used with the collector tied to the base.

The LM95231's TruTherm technology allows accurate sensing of integrated thermal diodes, such as those found

on processors. With TruTherm technology turned off, the LM95231 can measure a diode connected transistor

such as the MMBT3904.

The LM95231 has been optimized to measure the remote thermal diode integrated in a Pentium 4 processor on

90nm process or an MMBT3904 transistor. Using the Remote Diode Model Select register either pair of remote

inputs can be assigned to be either a Pentium 4 processor on 90nm process or an MMBT3904.

DIODE NON-IDEALITY

Diode Non-Ideality Factor Effect on Accuracy

When a transistor is connected as a diode, the following relationship holds for variables VBE, T and IF:

where

•

• q = 1.6×10−19 Coulombs (the electron charge),

• T = Absolute Temperature in Kelvin

• k = 1.38×10−23joules/K (Boltzmann's constant),

•ηis the non-ideality factor of the process the diode is manufactured on,

• IS= Saturation Current and is process dependent,

• If= Forward Current through the base emitter junction

• VBE = Base Emitter Voltage drop (1)

In the active region, the -1 term is negligible and may be eliminated, yielding the following equation

(2)

In Equation 2,ηand ISare dependant upon the process that was used in the fabrication of the particular diode.

By forcing two currents with a very controlled ratio(IF2/IF1) and measuring the resulting voltage difference, it is

possible to eliminate the ISterm. Solving for the forward voltage difference yields the relationship:

Product Folder Links: LM95231

MMBT3904

LM95231

D1+

D1-

D2+

D2-

100 pF

Pentium® 4

PROCESSOR

100 pF

ICIR

IE = IF

T = 'VBE x q

IC2

K x k x ln IC1

T = 'VBE x q

K x k x ln IF2

IF1

'VBE = K x x ln IF2

IF1

K x T

LM95231

SNIS139E –FEBRUARY 2005–REVISED MARCH 2013

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(3)

Solving Equation 3 for temperature yields:

(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. This wide non-ideality spread is not due to true process

variation but due to the fact that Equation 4 is an approximation.

TruTherm technology uses the transistor equation, Equation 5, which is a more accurate representation of the

topology of the thermal diode found in an FPGA or processor.

(5)

Figure 11. Thermal Diode Current Paths

TruTherm should only be enabled when measuring the temperature of a transistor integrated as shown in the

processor of Figure 11, because Equation 5 only applies to this topology.

Calculating Total System Accuracy

The voltage seen by the LM95231 also includes the IFRSvoltage drop of the series resistance. The non-ideality

factor, η, is the only other parameter not accounted for and depends on the diode that is used for measurement.

Since ΔVBE is proportional to both ηand T, the variations in ηcannot be distinguished from variations in

temperature. Since the non-ideality factor is not controlled by the temperature sensor, it will directly add to the

inaccuracy of the sensor. For the Pentium 4 processor on 90nm process, Intel specifies a +1.19%/−0.27%

variation in ηfrom part to part when the processor diode is measured by a circuit that assumes diode equation,

Equation 4, as true. As an example, assume a temperature sensor has an accuracy specification of ±0.75°C at a

temperature of 65 °C (338 Kelvin) and the processor diode has a non-ideality variation of +1.19%/−0.27%. The

resulting system accuracy of the processor temperature being sensed will be:

TACC = ± 0.75°C + (+1.19% of 338 K) = +4.76 °C (6)

and TACC = ± 0.75°C + (−0.27% of 338 K) = −1.65 °C (7)

TrueTherm technology uses the transistor equation, Equation 5, resulting in a non-ideality spread that truly

reflects the process variation which is very small. The transistor equation non-ideality spread is ±0.1% for the

Pentium 4 processor on 90nm process. The resulting accuracy when using TruTherm technology improves to:

TACC = ±0.75°C + (±0.1% of 338 K) = ± 1.08 °C (8)

The next error term to be discussed is that due to the series resistance of the thermal diode and printed circuit

board traces. The thermal diode series resistance is specified on most processor data sheets. For the Pentium 4

processor on 90 nm process, this is specified at 3.33Ωtypical. The LM95231 accommodates the typical series

resistance of the Pentium 4 processor on 90 nm process. The error that is not accounted for is the spread of the

Pentium's series resistance, that is 3.242Ωto 3.594Ωor +0.264Ωto −0.088Ω. The equation to calculate the

temperature error due to series resistance (TER) for the LM95231 is simply:

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TER = RPCB x 0.62°C/:

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(9)

Solving Equation 9 for RPCB equal to +0.264Ωand −0.088Ωresults 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.

Equation 9 can also be used to calculate the additional error caused by series resistance on the printed circuit

board. Since the variation of the PCB series resistance is minimal, the bulk of the error term is always positive

and can simply be cancelled out by subtracting it from the output readings of the LM95231.

Processor Family Diode Equation ηD, non-ideality Series R

min typ max

Pentium III CPUID 67h 1 1.0065 1.0125

Pentium III CPUID 68h/PGA370Socket/ 1.0057 1.008 1.0125

Celeron

Pentium 4, 423 pin 0.9933 1.0045 1.0368

Pentium 4, 478 pin 0.9933 1.0045 1.0368

Pentium 4 on 0.13 micron process, 2-3.06GHz 1.0011 1.0021 1.0030 3.64 Ω

Pentium 4 on 90 nm process 1.0083 1.011 1.023 3.33 Ω

Pentium M Processor (Centrino) 1.00151 1.00220 1.00289 3.06 Ω

MMBT3904 1.003

AMD Athlon MP model 6 1.002 1.008 1.016

AMD Athlon 64 1.008 1.008 1.096

AMD Opteron 1.008 1.008 1.096

AMD Sempron 1.00261 0.93 Ω

Compensating for Different Non-Ideality

In order to compensate for the errors introduced by non-ideality, the temperature sensor is calibrated for a

particular processor. Texas Instruments temperature sensors are always calibrated to the typical non-ideality and

series resistance of a given processor type. The LM95231 is calibrated for two non-ideality factors and series

resistance values thus supporting the MMBT3904 transistor and the Pentium 4 processor on 90nm process

without the requirement for additional trims. For most accurate measurements TruTherm mode should be turned

on when measuring the Pentium 4 processor on the 90nm process to minimize the error introduced by the false

non-ideality spread (see Diode Non-Ideality Factor Effect on Accuracy). When a temperature sensor calibrated

for a particular processor type is used with a different processor type, additional errors are introduced.

Temperature errors associated with non-ideality of different processor types may be reduced in a specific

temperature range of concern through use of software calibration. Typical Non-ideality specification differences

cause a gain variation of the transfer function, therefore the center of the temperature range of interest should be

the target temperature for calibration purposes. The following equation can be used to calculate the temperature

correction factor (TCF) required to compensate for a target non-ideality differing from that supported by the

LM95231.

TCF = [(ηS−ηProcessor) ÷ ηS] × (TCR+ 273 K) (10)

where

•ηS= LM95231 non-ideality for accuracy specification

•ηT= target thermal diode typical non-ideality

• TCR = center of the temperature range of interest in °C

The correction factor of Equation 10 should be directly added to the temperature reading produced by the

LM95231. For example when using the LM95231, with the 3904 mode selected, to measure a AMD Athlon

processor, with a typical non-ideality of 1.008, for a temperature range of 60 °C to 100 °C the correction factor

would calculate to:

TCF=[(1.003−1.008)÷1.003]×(80+273) =−1.75°C (11)

Therefore, 1.75°C should be subtracted from the temperature readings of the LM95231 to compensate for the

differing typical non-ideality target.

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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. VDD should be bypassed with a 0.1µF capacitor in parallel with 100pF. The 100pF capacitor should be placed

as close as possible to the power supply pin. A bulk capacitance of approximately 10µF needs to be in the

near vicinity of the LM95231.

2. A 100pF diode bypass capacitor is recommended to filter high frequency noise but may not be necessary.

Make sure the traces to the 100pF capacitor are matched. Place the filter capacitors close to the LM95231

pins.

3. Ideally, the LM95231 should be placed within 10cm of the Processor diode pins with the traces being as

straight, short and identical as possible. Trace resistance of 1Ωcan cause as much as 0.62°C of error. This

error can be compensated by using simple software offset compensation.

4. Diode traces should be surrounded by a GND guard ring to either side, above and below if possible. This

GND guard should not be between the D+ and D−lines. In the event that noise does couple to the diode

lines it would be ideal if it is coupled common mode. That is equally to the D+ and D−lines.

5. Avoid routing diode traces in close proximity to power supply switching or filtering inductors.

6. Avoid running diode traces close to or parallel to high speed digital and bus lines. Diode traces should be

kept at least 2cm apart from the high speed digital traces.

7. If it is necessary to cross high speed digital traces, the diode traces and the high speed digital traces should

cross at a 90 degree angle.

8. The ideal place to connect the LM95231's GND pin is as close as possible to the Processors GND

associated with the sense diode.

9. Leakage current between D+ and GND and between D+ and D−should be kept to a minimum. Thirteen

nano-amperes of leakage can cause as much as 0.2°C of error in the diode temperature reading. Keeping

the printed circuit board as clean as possible will minimize leakage current.

Noise coupling into the digital lines greater than 400mVp-p (typical hysteresis) and undershoot less than 500mV

below GND, may prevent successful SMBus communication with the LM95231. SMBus no acknowledge is the

most common symptom, causing unnecessary traffic on the bus. Although the SMBus maximum frequency of

communication is rather low (100kHz max), care still needs to be taken to ensure proper termination within a

system with multiple parts on the bus and long printed circuit board traces. An RC lowpass filter with a 3db

corner frequency of about 40MHz is included on the LM95231's SMBCLK input. Additional resistance can be

added in series with the SMBDAT and SMBCLK lines to further help filter noise and ringing. Minimize noise

coupling by keeping digital traces out of switching power supply areas as well as ensuring that digital lines

containing high speed data communications cross at right angles to the SMBDAT and SMBCLK lines.

Product Folder Links: LM95231

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 .......................................................................................................... 22

Product Folder Links: LM95231

PACKAGE OPTION ADDENDUM

www.ti.com 23-Aug-2017

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM95231BIMM-1/NOPB ACTIVE VSSOP DGK 8 1000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM 0 to 85 T25B

LM95231CIMM-1/NOPB ACTIVE VSSOP DGK 8 1000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM 0 to 85 T25C

LM95231CIMM-2/NOPB ACTIVE VSSOP DGK 8 1000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM 0 to 85 T26C

LM95231CIMM/NOPB ACTIVE VSSOP DGK 8 1000 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM 0 to 85 T23C

LM95231CIMMX/NOPB ACTIVE VSSOP DGK 8 3500 Green (RoHS

& no Sb/Br) CU SN Level-1-260C-UNLIM 0 to 85 T23C

(1) The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance

do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may

reference these types of products as "Pb-Free".

RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.

Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based

flame retardants must also meet the <=1000ppm threshold requirement.

(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation

of the previous line and the two combined represent the entire Device Marking for that device.

(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish

value exceeds the maximum column width.

PACKAGE OPTION ADDENDUM

www.ti.com 23-Aug-2017

Addendum-Page 2

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.

TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

LM95231BIMM-1/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1

LM95231CIMM-1/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1

LM95231CIMM-2/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1

LM95231CIMM/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1

LM95231CIMMX/NOPB VSSOP DGK 8 3500 330.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1

PACKAGE MATERIALS INFORMATION

www.ti.com 24-Aug-2017

Pack Materials-Page 1

*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

LM95231CIMM-1/NOPB VSSOP DGK 8 1000 210.0 185.0 35.0

LM95231CIMM-2/NOPB VSSOP DGK 8 1000 210.0 185.0 35.0

LM95231CIMM/NOPB VSSOP DGK 8 1000 210.0 185.0 35.0

LM95231CIMMX/NOPB VSSOP DGK 8 3500 367.0 367.0 35.0

PACKAGE MATERIALS INFORMATION

www.ti.com 24-Aug-2017

Pack Materials-Page 2

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LM95231BIMM LM95231BIMM-1 LM95231BIMM-1/NOPB LM95231BIMM-2 LM95231BIMM-2/NOPB

LM95231BIMM/NOPB LM95231BIMMX LM95231BIMMX-1 LM95231BIMMX-1/NOPB LM95231BIMMX-2

LM95231BIMMX-2/NOPB LM95231BIMMX/NOPB LM95231CIMM LM95231CIMM-1/NOPB LM95231CIMM-2

LM95231CIMM-2/NOPB LM95231CIMM/NOPB LM95231CIMMX LM95231CIMMX-1 LM95231CIMMX-1/NOPB

LM95231CIMMX-2 LM95231CIMMX-2/NOPB LM95231CIMMX/NOPB