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
FEATURES
KEY SPECIFICATIONS
•
•
•
•
•
1
2
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Accurately Senses Die Temperature of Remote
ICs or Diode Junctions
Uses TruTherm Technology for Precision
“Thermal Diode” Temperature Measurement
Thermal Diode Input Stage with Analog
Filtering
Thermal Diode Digital Filtering
Intel Pentium 4 Processor on 90nm Process or
2N3904 Non-ideality Selection
Remote Diode Fault Detection
On-board Local Temperature Sensing
Remote Temperature Readings Without Digital
Filtering:
– 0.125°C LSb
– 10-bits Plus Sign or 11-bits Programmable
Resolution
– 11-bits Resolves Temperatures Above
127 °C
Remote Temperature Readings with Digital
Filtering:
– 0.03125°C LSb with Filtering
– 12-bits Plus Sign or 13-bits Programmable
Resolution
– 13-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
Remote Temperature Accuracy ±0.75°C (max)
Local Temperature Accuracy ±3.0°C (max)
Supply Voltage 3.0V to 3.6V
Supply Current 402μA (typ)
APPLICATIONS
•
•
•
Processor/Computer System Thermal
Management
– e.g. Laptop, Desktop, Workstations, Server)
Electronic Test Equipment
Office Electronics
DESCRIPTION
The LM95231 is a precision dual remote diode
temperature sensor (RDTS) that uses Texas
Instruments' TruTherm technology. The 2-wire serial
interface of the LM95231 is compatible with SMBus
2.0. The LM95231 can sense three temperature
zones, it can measure the temperature of its own die
as well as two diode connected transistors. The
LM95231 includes digital filtering and an advanced
input stage that includes analog filtering and
TruTherm technology that reduces processor-toprocessor non-ideality spread. The diode connected
transistors can be a “thermal diode” as found in Intel
and AMD processors or can simply be a diode
connected
MMBT3904
transistor.
TruTherm
technology allows accurate measurement of “thermal
diodes” found on small geometry processes, 90nm
and below. The LM95231 supports user selectable
thermal diode non-ideality of either a Pentium 4
processor on 90nm process or 2N3904.
The LM95231 resolution format for remote
temperature readings can be programmed to be 11bits signed or unsigned with the digital filtering
disabled. When the filtering is enabled the resolution
increases to 13-bits signed or unsigned. In the
unsigned mode the LM95231 remote diode readings
can resolve temperatures above 127°C. Local
temperature readings have a resolution of 9-bits plus
sign.
1
2
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.
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 © 2005–2013, Texas Instruments Incorporated
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.
** Optional may be required in noisy systems; place close to LM95231 pins.
PIN DESCRIPTIONS
2
Label
Pin #
Function
D1+
1
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 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.
Typical Connection
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 diodeconnected 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
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LM95231
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SNIS139E – FEBRUARY 2005 – REVISED MARCH 2013
Simplified Block Diagram
3.0V-3.6V
LM95231
Local
Diode Selector
D+
D-
Remote
Diode1 Selector
D+
D-
Remote
Diode2 Selector
Control
Logic
Local
Temperature
Registers
'-6 Converter
11-Bit or 10-Bit Plus Sign Remote
9-bit Plus Sign Local
TruThermTM
Temperature
Sensor
Circuitry
Remote 1
Temperature
Registers
Remote 2
Temperature
Registers
Diode Type
Selection
Register
Diode
TruTherm
Control
Register
Diode Filter
Control
Registers
SMBus Two Wire Serial Interface
Config
and
Status
Registrer
Revision &
Manufacturer
ID Registers
SMBDAT
SMBCLK
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
−0.3 V to 6.0 V−0.5V to 6.0V
Voltage at SMBDAT, SMBCLK
−0.3 V to (VDD + 0.3 V)
Voltage at Other Pins
Input Current at All Pins (2)
Package Input Current
±5 mA
(2)
30 mA
SMBDAT Output Sink Current
10 mA
Junction Tempeature (3)
125°C
−65°C to +150°C
Storage Temperature
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)
(2)
(3)
(4)
(5)
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.
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.
Thermal resistance junction-to-ambient when attached to a printed circuit board with 1oz. foil and no airflow:
— VSSOP-8 = 210°C/W
Human body model, 100pF discharged through a 1.5kΩ resistor. Machine model, 200pF discharged directly into each pin.
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)
(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. 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.
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. TJ is the junction temperature of the LM95231. TD is the
junction temperature of the remote thermal diode.
PARAMETER
1)
TA = 0°C to +85°C (3) (4)
Accuracy Using Local Diode
Accuracy Using Remote Diode, see
for Thermal Diode Processor Type.
Typical (
TEST CONDITIONS
(5)
±1
LM9523 LM9523
1
1
BIMM
CIMM
(2)
Limits
Limits (2)
±3
±3
UNIT
°C (max)
TA = +20°C to +40°C; TD =
+45°C to +85°C
Intel 90nm Thermal
Diode
±0.75
°C (max)
TA = +20°C to +40°C; TD =
+45°C to +85°C
MMBT3904 Thermal
Diode
±1.25
°C (max)
TA = +20°C to +40°C; TD =
+45°C to +85°C
Intel 90nm and
MMBT3904 Thermal
Diodes
TA = +0°C to +85°C; TD =
+25°C to +140°C
Intel 90nm and
MMBT3904 Thermal
Diodes
±2.5
±1.25
°C (max)
±2.5
°C (max)
Remote Diode Measurement Resolution
with filtering turned off
10+sign/
11
0.125
°C
Remote Diode Measurement Resolution
with digital filtering turned on
12+sign/
13
Bits
Local Diode Measurement Resolution
Conversion Time of All Temperatures at
the Fastest Setting
Average Quiescent Current (7)
See
(6)
TruTherm Mode Disabled
(2)
(3)
(4)
(5)
(6)
(7)
4
0.03125
°C
9+sign
Bits
0.25
°C
75.8
83.9
83.9
ms
(max)
TruTherm Mode enabled
79.2
87.7
87.7
ms
(max)
SMBus Inactive, 1 Hz conversion rate
402
545
545
µA (max)
Shutdown
272
µA
0.4
V
D− Source Voltage
(1)
Bits
Typicals are at TA = 25°C and represent most likely parametric norm at time of product characterization. The typical specifications are
not ensured.
Limits are specified to AOQL (Average Outgoing Quality Level).
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.
Thermal resistance junction-to-ambient when attached to a printed circuit board with 1oz. foil and no airflow:
— VSSOP-8 = 210°C/W
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.
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).
Quiescent current will not increase substantially when the SMBus is active.
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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.
PARAMETER
Typical (
TEST CONDITIONS
1)
Diode Source Current Ratio
LM9523 LM9523
1
1
BIMM
CIMM
Limits (2) Limits (2)
UNIT
16
Diode Source Current
Power-On Reset Threshold
(VD+ − VD−) = + 0.65V;
high-level
176
Low-level
11
Measure on VDD input, falling edge
300
300
µA (max)
100
100
µA (min)
2.7
1.8
2.7
1.8
V (max)
V (min)
µA
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
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
400
mV
5
pF
SMBDAT OUTPUT
IOH
High Level Output Current
VOH = VDD
10
µA (max)
VOL
SMBus Low Level Output Voltage
IOL = 4mA
IOL = 6mA
0.4
0.6
V (max)
(1)
(2)
Typicals are at TA = 25°C and represent most likely parametric norm at time of product characterization. The typical specifications are
not ensured.
Limits are specified to AOQL (Average Outgoing Quality Level).
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LM95231
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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
SMBus Clock Frequency
tLOW
SMBus Clock Low Time
from VIN(0)max to VIN(0)max
Limits (2)
Units
(Limit)
100
10
kHz (max)
kHz (min)
4.7
25
µs (min)
ms (max)
tHIGH
SMBus Clock High Time
from VIN(1)min to VIN(1)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,
IO = 3mA (4)
4.0
µs (min)
250
ns (max)
SMBDAT and SMBCLK Time Low for Reset of
Serial Interface (5)
25
35
ms (min)
ms (max)
tSU;DAT
Data In Setup Time to SMBCLK High
250
ns (min)
tHD;DAT
Data Out Stable after SMBCLK Low
300
1075
ns (min)
ns (max)
tHD;STA
Start Condition SMBDAT Low to SMBCLK Low
(Start condition hold before the first clock falling
edge)
100
ns (min)
tSU;STO
Stop Condition SMBCLK High to SMBDAT Low
(Stop Condition Setup)
100
ns (min)
tSU;STA
SMBus Repeated Start-Condition Setup Time,
SMBCLK High to SMBDAT Low
0.6
µs (min)
SMBus Free Time Between Stop and Start
Conditions
1.3
µs (min)
tBUF
(2)
(3)
(4)
(5)
Typical (1)
Conditions
fSMB
tTIMEOUT
(1)
Parameter
Typicals are at TA = 25°C and represent most likely parametric norm at time of product characterization. The typical specifications are
not ensured.
Limits are specified to AOQL (Average Outgoing Quality Level).
The output rise time is measured from (VIN(0)max + 0.15V) to (VIN(1)min − 0.15V).
The output fall time is measured from (VIN(1)min - 0.15V) to (VIN(1)min + 0.15V).
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.
tLOW
tR
tF
VIH
SMBCLK
VIL
tHD;STA
tHD;DAT
tBUF
tHIGH
tSU;STA
tSU;DAT
tSU;STO
VIH
SMBDAT
VIL
P
S
S
P
Figure 2. SMBus Communication
6
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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
6.5V
GND
6
B
7
C
8
C
Circuit B
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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.
8
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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. 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-significantbit (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
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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.
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 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:
10
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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 .
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
FF00h
−1°C
1111 1111 0000 0000
−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 16bit 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
12
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
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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
A Write 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
Register will point to one of the Read Temperature Registers because that will be the data most frequently
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.
1
9
1
9
SMBCLK
SMBDAT
A6
A5
A4
A3
A2
A1
D7
Ack
by
LM95231
A0 R/W
Start by
Master
D6
D5
Frame 1
Serial Bus Address Byte
D4
D3
D2
Frame 2
Command Byte
D1
D0
Ack by Stop
LM95231 by
Master
Figure 7. Serial Bus Write to the Internal Command Register
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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. Serial Bus Write to the internal Command Register followed by a Data Byte
1
9
1
9
SMBCLK
SMBDAT
A6
A5
A4
A3
A2
A1
D7
Ack
by
LM95231
A0 R/W
Start by
Master
D6
D5
D4
D3
D2
D1
D0
NoAck Stop
by
by
Master Master
Frame 1
Serial Bus Address Byte
Frame 2
Data Byte from the LM95231
Figure 9. Serial Bus byte Read from a Register with the internal Command Register preset to desired
value.
1
9
1
9
SMBCLK
SMBDAT
A6
A5
A4
A3
A2
D7
Ack
by
LM95231
A1
D6
A0 R/W
Start by
Master
D5
Frame 1
Serial Bus Address Byte
SMBCLK
(Continued)
SMBDAT
(Continued)
9
A5
A4
A3
A2
A1
D3
D2
D1
D0
Ack
Repeat
by
Start by
LM95231 Master
Frame 2
Command Byte
1
A6
D4
1
D7
Ack
by
LM95231
A0 R/W
Frame 3
Serial Bus Address Byte
9
D6
D5
D4
D3
D2
D1
D0
No Ack Stop
by
by
Master Master
Frame 4
Data Byte from the LM95231
(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 2535ms. 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
(Hex)
Power-On
Default Value
(Hex)
Read/Write
# of used bits
Comments
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
Select
30h
01h
R/W
2
Selects the 2N3904 or Pentium
4 processor on 90nm process
thermal diode model
Remote Diode TruTherm Mode
Control
07h
01h
8
Enables or disables TruTherm
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
D5
D4
D3
D2
D1
D0
R2TME
R1TME
RD2M
RD1M
STATUS REGISTER
D7
D6
Busy
Reserved
0
0
0
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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
(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.
2
Remote 1 TruTherm Mode Enabled
(R2TME)
When set to "1" indicates that the TruTherm Mode has been activated for
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.
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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:
IF = IS x e
VBE
K x Vt
-1
where
•
•
•
•
•
•
•
•
kT
Vt = q
q = 1.6×10−19 Coulombs (the electron charge),
T = Absolute Temperature in Kelvin
k = 1.38×10−23joules/K (Boltzmann's constant),
η is 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
Vbe
KV
IF = IS e t
(2)
In Equation 2, η and IS are 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 IS term. Solving for the forward voltage difference yields the relationship:
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'VBE = K x K qx T x ln
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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. 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.
T=
'VBE x q
IC2
K x k x ln
IC1
(5)
Pentium® 4
PROCESSOR
IE = IF
100 pF
1
2
3
IC IR
100 pF
4
D1+
D1D2+
D2-
IF
Q1
MMBT3904
LM95231
IR
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 IFRS voltage 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 η and T, the variations in η cannot 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 η from 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)
TACC = ± 0.75°C + (−0.27% of 338 K) = −1.65 °C
(7)
and
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 3.33Ω typical. 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 3.242Ω to 3.594Ω or +0.264Ω to −0.088Ω. The equation to calculate the
temperature error due to series resistance (TER) for the LM95231 is simply:
20
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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.
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.
Diode Equation ηD, non-ideality
Processor Family
Series R
min
typ
max
1
1.0065
1.0125
Pentium III CPUID 68h/PGA370Socket/
Celeron
1.0057
1.008
1.0125
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 III CPUID 67h
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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21
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. 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 1Ω can 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.
22
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LM95231
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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
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23
PACKAGE OPTION ADDENDUM
www.ti.com
23-Sep-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
LM95231BIMM
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T23B
LM95231BIMM-1
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T25B
LM95231BIMM-1/NOPB
ACTIVE
VSSOP
DGK
8
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T25B
LM95231BIMM-2
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T26B
LM95231BIMM-2/NOPB
ACTIVE
VSSOP
DGK
8
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T26B
LM95231BIMM/NOPB
ACTIVE
VSSOP
DGK
8
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T23B
LM95231BIMMX
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T23B
LM95231BIMMX-1
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T25B
LM95231BIMMX-1/NOPB
ACTIVE
VSSOP
DGK
8
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T25B
LM95231BIMMX-2
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T26B
LM95231BIMMX-2/NOPB
ACTIVE
VSSOP
DGK
8
3500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T26B
LM95231BIMMX/NOPB
ACTIVE
VSSOP
DGK
8
3500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T23B
LM95231CIMM
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T23C
LM95231CIMM-1
ACTIVE
VSSOP
DGK
8
1000
TBD
Call TI
Call TI
0 to 85
T25C
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
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T26C
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
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T23C
1000
3500
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
Orderable Device
23-Sep-2013
Status
(1)
Package Type Package Pins Package
Drawing
Qty
LM95231CIMMX-1
ACTIVE
VSSOP
DGK
8
LM95231CIMMX-1/NOPB
ACTIVE
VSSOP
DGK
8
LM95231CIMMX-2
ACTIVE
VSSOP
DGK
8
LM95231CIMMX-2/NOPB
ACTIVE
VSSOP
DGK
8
LM95231CIMMX/NOPB
ACTIVE
VSSOP
DGK
8
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
TBD
Call TI
Call TI
0 to 85
T25C
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T25C
TBD
Call TI
Call TI
0 to 85
T26C
3500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T26C
3500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T23C
3500
(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)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
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.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(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.
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.
Addendum-Page 2
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
23-Sep-2013
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.
Addendum-Page 3
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
12.0
Q1
LM95231BIMMX-1/NOPB VSSOP
DGK
8
3500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM95231BIMMX-2/NOPB VSSOP
DGK
8
3500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM95231BIMMX/NOPB
VSSOP
DGK
8
3500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM95231CIMM-1
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-1/NOPB VSSOP
DGK
8
3500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM95231CIMMX-2/NOPB VSSOP
DGK
8
3500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
DGK
8
3500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM95231CIMMX/NOPB
VSSOP
Pack Materials-Page 1
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
35.0
LM95231BIMMX/NOPB
VSSOP
DGK
8
3500
367.0
367.0
35.0
LM95231CIMM-1
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-1/NOPB
VSSOP
DGK
8
3500
367.0
367.0
35.0
LM95231CIMMX-2/NOPB
VSSOP
DGK
8
3500
367.0
367.0
35.0
LM95231CIMMX/NOPB
VSSOP
DGK
8
3500
367.0
367.0
35.0
Pack Materials-Page 2
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