LM95241
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SNIS143E – AUGUST 2006 – REVISED MARCH 2013
LM95241 Dual Remote Diode Temperature Sensor with SMBus Interface and TruTherm™
Technology (65nm/90nm)
Check for Samples: LM95241
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 Processor on 65nm or 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 Diode Temperature Accuracy
– TA = 20°C to 40°C, TD = 45°C to 85°C ±1.25
°C (Max)
– TA = 0°C to 85°C, TD = 25°C to 140°C ±2.5 °C
(Max)
Local Temperature Accuracy
– TA = 0°C to 85°C ±3.0 °C (Max)
Supply Voltage 3.0 V to 3.6 V
Average Supply Current 471 μA (Typ)
APPLICATIONS
•
•
•
Processor/Computer System Thermal
Management
– (e.g. Laptop, Desktop, Workstations,
Server)
Electronic Test Equipment
Office Electronics
DESCRIPTION
The LM95241 is a precision dual remote diode
temperature sensor (RDTS) that uses TI's TruTherm
technology. The 2-wire serial interface of the
LM95241 is compatible with SMBus 2.0. The
LM95241 can sense three temperature zones, it can
measure the temperature of its own die as well as
two diode connected transistors. The LM95241
includes digital filtering and an advanced input stage
that includes analog filtering and TruTherm
technology that reduces processor-to-processor nonideality 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 such as 90nm and 65nm.
The LM95241 supports user selectable thermal diode
non-ideality of either Intel processor on 90nm or
65nm process or 2N3904.
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 © 2006–2013, Texas Instruments Incorporated
LM95241
SNIS143E – AUGUST 2006 – REVISED MARCH 2013
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DESCRIPTION (CONTINUED)
The LM95241 resolution format for remote temperature readings can be programmed to be 11-bits 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 LM95241 remote diode readings can resolve temperatures above 127°C.
Local temperature readings have a resolution of 9-bits plus sign.
Connection Diagram
D1+
1
D1-
2
8
SMBCLK
7
D2+
3
6
SMBDAT
VDD
D2-
4
5
GND
LM95241
Figure 1. VSSOP-8
TOP VIEW
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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Simplified Block Diagram
3.0V-3.6V
LM95241
Local
Diode Selector
D+
DD+
D-
'-6 Converter
11-Bit or 10-Bit Plus Sign Remote
9-bit Plus Sign Local
TruThermTM
Temperature
Sensor
Circuitry
Remote
Diode1 Selector
Remote
Diode2 Selector
Local
Remote 1
Remote 2
Diode Type
Control Temperature Temperature Temperature Selection
Logic
Registers
Registers
Registers
Register
Diode
TruTherm
Control
Register
Config
and
Status
Register
Diode Filter
Control
Registers
Revision and
Manufacturer
ID Registers
SMBDAT
SMBCLK
SMBus Two Wire Serial Interface
Typical Application
+3.3V
Standby
C4**
100 pF
65nm/90nm
PROCESSOR
1
2
3
C5**
100 pF
4
D1+
D1D2+
D2-
SMBCLK
7
SMBDAT
VDD 6
5
GND
LM95241
Q1
MMBT3904
R2
1.3k
R1
1.3k
8
SMBCLK
SMBDAT
C1*
100 pF
C2
0.1 PF
C3
10 PF
+
SMBus
Master
* Place close to LM95241 pins.
** Optional may be required in noisy systems; place close to LM95241 pins.
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.
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Absolute Maximum Ratings (1)
−0.3 V to 6.0 V
Supply Voltage
−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 Temperature (3)
+125°C
−65°C to +150°C
Storage Temperature
ESD Susceptibility (4)
Human Body Model
Machine Model
Charged Device Model Model
2000 V
200 V
1000 V
For soldering specifications, see http://www.ti.com/lit/SNOA549. (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 conditions 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 LM95241'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 air flow:
— VSSOP-8 = 210°C/W
Human body model (HBM), 100pF discharged through a 1.5kΩ resistor. Machine model (MM), 200pF discharged directly into each pin.
Charged Device Model (CDM) simulates a pin slowly acquiring charge (such as from a device sliding down the feeder in an automated
assembler) then rapidly being discharged.
Reflow temperature profiles are different for packages containing lead (Pb) than for those that do not.
Operating Ratings (1) (2)
Operating Temperature Range
0°C to +125°C
Electrical Characteristics Temperature Range
TMIN≤TA≤TMAX
LM95241CIMM
0°C≤TA≤+85°C
Supply Voltage Range (VDD)
+3.0V to +3.6V
(1)
(2)
4
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 conditions 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 air flow:
— VSSOP-8 = 210°C/W
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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 LM95241. TD is the
junction temperature of the remote thermal diode.
Parameter
Conditions
TA = 0°C to +85°C (3)
Accuracy Using Local Diode
Accuracy Using Remote Diode, see
Diode Processor Type.
(4)
for Thermal
Typical (1)
Limits (2)
Units
(Limit)
±1
±3
°C (max)
TA = +20°C to
+40°C
TD = +45°C to
+85°C
±1.25
°C (max)
TA = +0°C to +85°C
TD = +25°C to
+140°C
±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
Bits
0.03125
°C
9+sign
Bits
0.25
Conversion Time of All Temperatures at the Fastest
Setting (5)
Average Quiescent Current (6)
76.5
86.1
ms (max)
TruTherm Mode Enabled for All
Remote Channels
79.1
88.9
ms (max)
SMBus Inactive, 1 Hz conversion
rate
471
640
µA (max)
Shutdown
356
µA
0.4
V
D− Source Voltage
Diode Source Current Ratio
Diode Source Current
16
(VD+ − VD−)=+ 0.65V; high-level
Low-level
Power-On Reset Threshold
(1)
(2)
(3)
(4)
(5)
(6)
°C
TruTherm Mode Disabled for All
Remote Channels
Measure on VDD input, falling edge
172
230
µA (max)
100
µA (min)
2.7
1.6
V (max)
V (min)
11
µA
Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical
specifications are not ensured.
Limits are specified to Texas Instruments' 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 LM95241 and the thermal resistance. See Note 2 of the Operating Ratings table for the thermal
resistance to be used in the self-heating calculation.
The accuracy of the LM95241CIMM is ensured when using a typical thermal diode of an Intel processor on a 65 nm process or an
MMBT3904 diode-connected transistor, as selected in the Remote Diode Model Select register. See typical performance curve for
performance with Intel processor on a 90nm process.
This specification is provided only to indicate how often temperature data is updated. The LM95241 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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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)
Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical
specifications are not ensured.
Limits are specified to Texas Instruments' AOQL (Average Outgoing Quality Level).
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 LM95241 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 LM95241. They
adhere to but are not necessarily the SMBus bus specifications.
Symbol
(2)
(3)
(4)
(5)
6
Conditions
fSMB
SMBus Clock Frequency
tLOW
SMBus Clock Low Time
from VIN(0)max to VIN(0)max
Typical (1)
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)
tTIMEOUT
(1)
Parameter
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)
Typical figures are at TA = 25°C and represent most likely parametric norms at the time of product characterization. The typical
specifications are not ensured.
Limits are specified to Texas Instruments' 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 LM95241's SMBus state machine,
therefore setting SMBDAT and SMBCLK pins to a high impedance state.
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Logic Electrical Characteristics SMBus Digital Switching Characteristics (continued)
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 LM95241 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 LM95241. They
adhere to but are not necessarily the SMBus bus specifications.
Symbol
tBUF
Parameter
Typical (1)
Conditions
SMBus Free Time Between Stop and Start
Conditions
Limits (2)
Units
(Limit)
1.3
µs (min)
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
Table 1. Parasitic components and ESD protection circuitry
Pin
#
Label
Circ
uit
1
D1+
A
2
D1−
A
3
D2+
A
4
D2−
A
5
GND
B
6
VDD
B
7
SMBDAT
C
8
SMBCLK
C
All Input ESD Protection Structure Circuits
V+
V+
D2
ESD
Clamp
PIN
D1
D3
6.5V
ESD
CLAMP
D2
160 k
D3
80 k
D1
6.5V
GND
GND
PIN
D1
SNP
GND
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Typical Performance Characteristics
8
Intel Processor on 65nm Process or 90nm Process Thermal
Diode Performance Comparison
Thermal Diode Capacitor or PCB Leakage Current Effect
Remote Diode Temperature Reading
Figure 3.
Figure 4.
Remote Temperature Reading Sensitivity to Thermal Diode
Filter Capacitance
Conversion Rate Effect on Average Power Supply Current
Figure 5.
Figure 6.
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FUNCTIONAL DESCRIPTION
The LM95241 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 LM95241 can support two external transistor types, a
Intel processor on 65nm or 90mn process thermal diode or a 2N3904 diode connected transistor. The transistor
type is register programmable and does not require software intervention after initialization. The LM95241 has an
advanced input stage using Texas Instruments' TruTherm technology that reduces the spread in non-ideality
found in Intel processors on 65nm or 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 LM95241, 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
LM95241 to the system requirements. The LM95241 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 LM95241 remote diode temperature accuracy is trimmed for the typical thermal diode of a Intel processor on
65nm or 90nm process or a typical 2N3904 transistor and the accuracy is ensured only when using either of
these diodes when selected appropriately. TruTherm mode should be enabled when measuring a Intel processor
on 65nm or 90nm process and disabled when measuring a 3904 transistor.
Diode fault detection circuitry in the LM95241 can detect the presence of a remote diode.
The LM95241 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 LM95241 typically takes 77.8 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 88.9
ms. Different conversion rates will cause the LM95241 to draw different amounts of supply current as shown in
Figure 7.
Figure 7. Conversion Rate Effect on Power Supply Current
POWER-ON-DEFAULT STATES
LM95241 always powers up to these known default states. The LM95241 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 Intel processor on 65nm or 90nm process with TruTherm Mode enabled.
Remote Diode 2 model is set to 2N3904/MMBT3904 with TruTherm mode disabled.
6. Status Register depends on state of thermal diode inputs
7. Configuration register set to 00h; continuous conversion
SMBus INTERFACE
The LM95241 operates as a slave on the SMBus, so the SMBCLK line is an input and the SMBDAT line is
bidirectional. The LM95241 never drives the SMBCLK line and it does not support clock stretching. According to
SMBus specifications, the LM95241 has a 7-bit slave address. All bits A6 through A0 are internally programmed
and cannot be changed by software or hardware. The SMBus slave address is dependent on the LM95241 part
number ordered:
Version
A6
A5
A4
A3
A2
A1
A0
LM95241CIMM
0
1
0
1
0
1
1
LM95241CIMM-1
0
0
1
1
0
0
1
LM95241CIMM-2
0
1
0
1
0
1
0
10
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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 16bit word available in two 8-bit registers. Unused bits will always report "0".
Table 4. 13-bit, 2's complement
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 0111
FFF7h
−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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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 +127.75°C are clamped to +127.75°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
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 LM95241. The maximum resistance of the pull-up to provide a 2.1V high
level, based on LM95241 specification for High Level Output Current with the supply voltage at 3.0V, is
82kΩ(5%) or 88.7kΩ(1%).
DIODE FAULT DETECTION
The LM95241 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.
COMMUNICATING WITH THE LM95241
The data registers in the LM95241 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 LM95241 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
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A Write to the LM95241 will always include the address byte and the command byte. A write to any register
requires one data byte.
Reading the LM95241 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 LM95241), 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 LM95241 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.
SMBus Timing Diagrams for Access of Data
1
9
1
9
SMBCLK
SMBDAT
A6
A5
A4
A3
A2
A1
D7
R/W
A0
D6
D5
D4
D3
D2
D1
Ack
by
LM95241
Start by
Master
D0
Ack by Stop
LM95241 by
Master
Frame 1
Serial Bus Address Byte
Frame 2
Command Byte
Figure 8. Serial Bus Write to the Internal Command Register
1
9
1
9
SMBCLK
SMBDAT
A6
A5
A4
A3
A2
A1
A0
R/W
D7
D6
D5
D4
D3
D2
D1
D0
Ack
by
LM95241
Start by
Master
Ack
by
LM95241
Frame 1
Serial Bus Address Byte
SMBCLK
(Continued)
SMBDAT
(Continued)
Frame 2
Command Byte
1
D7
9
D6
D5
D4
D3
D2
D1
D0
Ack by Stop
LM95241 by
Master
Frame 3
Data Byte
Figure 9. Serial Bus Write to the internal Command Register followed by a Data Byte
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1
9
1
9
SMBCLK
SMBDAT
A6
A4
A5
A3
A2
A1
A0
D7
R/W
D6
D5
D4
D3
D2
D1
D0
Ack
by
LM95241
Start by
Master
NoAck
Stop
by
by
Master Master
Frame 1
Serial Bus Address Byte
Frame 2
Data Byte from the LM95241
Figure 10. 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
A1
A0 R/W
Start by
Master
D7
Ack
by
LM95241
D6
D5
Frame 1
Serial Bus Address Byte
SMBCLK
(Continued)
SMBDAT
(Continued)
9
A5
A4
A3
A2
A1
Frame 3
Serial Bus Address Byte
D3
D2
D1
D0
Ack
Repeat
by
Start by
LM95241 Master
Frame 2
Command Byte
1
A6
D4
A0 R/W
1
D7
Ack
by
LM95241
9
D6
D5
D4
D3
D2
D1
D0
No Ack Stop
by
by
Master Master
Frame 4
Data Byte from the LM95241
Figure 11. Serial Bus Write followed by a Repeat Start and Immediate Read
SERIAL INTERFACE RESET
In the event that the SMBus Master is RESET while the LM95241 is transmitting on the SMBDAT line, the
LM95241 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 LM95241 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.
2. When SMBDAT is HIGH, have the master initiate an SMBus start. The LM95241 will respond properly to an
SMBus start condition at any point during the communication. After the start the LM95241 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.
LM95241 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.
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P7
P6
P5
P4
P3
P2
P1
P0
Command
P0-P7: Command
Table 6. Register Summary
Command
(Hex)
Name
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 Intel
processor on 65nm or 90nm
process thermal diode model
Remote Diode TruTherm Mode
Control
07h
01h
6
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 LM95241.
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
A4h
RO
D5
D4
STATUS REGISTER
(Read Only Address 02h):
D7
D6
Busy
Reserved
0
0
D3
D2
D1
D0
R2TME
R1TME
RD2M
RD1M
0
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. This bit will be set even if the diode is
desconnected.
2
Remote 1 TruTherm Mode Enabled
(R1TME)
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. This bit will be set even if the diode is
disconnected.
1
Remote Diode 2 Missing (RD2M)
When set to "1" Remote Diode 2 is missing. (See DIODE FAULT DETECTION
for further details.) 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 3904 transistor to Remote 2
inputs with TruTherm mode active may also cause this bit to be set.
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Bits
Name
Description
0
Remote Diode 1 Missing (RD1M)
When set to "1" Remote Diode 1 is missing. (See DIODE FAULT DETECTION
for further details.) 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 3904 transistor to Remote 1
inputs with TruTherm mode active may also cause this bit to be set.
CONFIGURATION REGISTER
(Read Address 03h /Write Address 03h):
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 76.5 ms, 13.1 Hz (typ), when TruTherm Mode is disabled
(Diode Equation) for both remote channels; 77.8 ms, 12.9 Hz (typ), when
TruTherm Mode is enabled (Transistor Equation) 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)
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 +127.75 °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 +127.75 °C)
0
Reserved
Reports "0" when read.
Power up default is with all bits “0” (zero)
REMOTE DIODE FILTER CONTROL REGISTER
(Read/write Address 06h):
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 1Filter Enable (R1FE)
0: Filter Off
1: Noise Filter On
Power up default is 05h.
REMOTE DIODE MODEL TYPE SELECT REGISTER
(Read/Write Address 30h):
16
D7
D6
D5
D4
D3
D2
D1
D0
0
0
0
0
0
R2MS
0
R1MS
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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: Intel processor on 65nm or 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: Intel processor on 65nm or 90nm process model (make sure TruTherm
mode is enabled)
Power up default is 1.
Power up default is 01h.
REMOTE DIODE TruTherm MODE CONTROL
(Read/Write Address 07h):
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.
LOCAL AND REMOTE MSB AND LSB TEMPERATURE REGISTERS
Local Temperature MSB
(Read Only Address 10h) 9-bit plus sign format:
BIT
D7
D6
D5
D4
D3
D2
D1
D0
Value
SIGN
64
32
16
8
4
2
1
Temperature Data: LSb = 1°C.
Local Temperature LSB
(Read Only Address 20h) 9-bit plus sign format:
BIT
D7
D6
D5
D4
D3
D2
D1
D0
Value
0.5
0.25
0
0
0
0
0
0
Temperature Data: LSb = 0.25°C.
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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.
Remote Temperature MSB
(Read Only Address 11h, 12h) 11-bit plus sign 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
(Read Only Address 21, 22h) 10-bit plus sign or 11-bit unsigned binary formats with filter off:
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.
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
0.0625
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.
DIE REVISION CODE REGISTER
(Read Address FFh) The default value is A4h. This register will increment by 1 every time there is a revision to
the die by Texas Instruments.
Applications Hints
The LM95241 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 LM95241'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 LM95241 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.
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To measure temperature external to the LM95241'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 LM95241'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 a 2N3904 transistor base emitter
junction be used with the collector tied to the base.
The LM95241's TruTherm technology allows accurate sensing of integrated thermal diodes, such as those found
on sub-micron geometry processors. With TruTherm technology turned off, the LM95241 can measure a diode
connected transistor such as the 2N3904 or MMBT3904.
The LM95241 has been optimized to measure the remote thermal diode integrated in a Intel processor on 65nm
or 90nm process or an MMBT3904 transistor. Using the Remote Diode Model Select register either pair of
remote inputs can be assigned to measure either a Intel processor on 65nm or 90nm process or an MMBT3904
transistor.
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
IF = IS e KVt
(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:
'VBE = K x K qx T x ln
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 12 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.
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'VBE x q
IC2
K x k x ln
IC1
(5)
65nm/90nm
PROCESSOR
IE = IF
100 pF
1
2
3
IC IR
100 pF
4
D1+
D1D2+
D2-
LM95241
IF
Q1
MMBT3904
IR
Figure 12. Thermal Diode Current Paths
TruTherm should only be enabled when measuring the temperature of a transistor integrated as shown in the
processor of Figure 12, because Equation 5 only applies to this topology.
Calculating Total System Accuracy
The voltage seen by the LM95241 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 D processor on 65nm process, Intel specifies a +4.06%/−0.89%
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 ±1.25°C at a
temperature of 65 °C (338 Kelvin) and the processor diode has a non-ideality variation of +4.06%/−0.89%. The
resulting system accuracy of the processor temperature being sensed will be:
TACC = + 1.25°C + (+4.06% of 338 K) = +14.97 °C
(6)
TACC = - 1.25°C + (−0.89% of 338 K) = −4.26 °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 ±0.4% for the
Pentium D processor on 65nm process. The resulting accuracy when using TruTherm technology improves to:
TACC = ±1.25°C + (±0.4% of 338 K) = ± 2.60 °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 D
processor on 65 nm process, this is specified at 4.52Ω typical. The LM95241 accommodates the typical series
resistance of the Pentium D processor on 65nm process. The error that is not accounted for is the spread of the
Pentium's series resistance, that is 2.79Ω to 6.24Ω or ±1.73Ω. The equation to calculate the temperature error
due to series resistance (TER) for the LM95241 is simply:
TER = RPCB x 0.62°C/ :
(9)
Solving Equation 9 for RPCB equal to ±1.73Ω results in the additional error due to the spread in the series
resistance of ±1.07°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 LM95241.
Processor Family
Intel processor on 65nm process
20
Transistor Equation nD, non-ideality
min
typ
max
0.997
1.001
1.005
Submit Documentation Feedback
Series R
4.52 Ω
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: LM95241
LM95241
www.ti.com
SNIS143E – AUGUST 2006 – REVISED MARCH 2013
Diode Equation ηD, non-ideality
Processor Family
Pentium III CPUID 67h
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 4 on 90 nm process
1.0083
1.011
1.023
3.33 Ω
Pentium on 65 nm porcess
Pentium M Processor (Centrino)
1.000
1.009
1.050
4.52 Ω
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 LM95241 is calibrated for two non-ideality factors and series
resistance values thus supporting the MMBT3904 transistor and the Intel processor on 65nm or 90nm process
without the requirement for additional trims. For most accurate measurements TruTherm mode should be turned
on when measuring the Intel processor on the 65nm or 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
LM95241.
TCF = [(ηS−ηProcessor) ÷ ηS] × (TCR+ 273 K)
where
•
•
•
ηS = LM95241 non-ideality for accuracy specification
ηT = target thermal diode typical non-ideality
TCR = center of the temperature range of interest in °C
(10)
The correction factor of Equation 10 should be directly added to the temperature reading produced by the
LM95233. For example when using the LM95241, 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 LM95241 to compensate for the
differing typical non-ideality target.
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Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: LM95241
21
LM95241
SNIS143E – AUGUST 2006 – REVISED MARCH 2013
www.ti.com
PCB LAYOUT FOR MINIMIZING NOISE
Figure 13. 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 LM95241 can cause temperature
conversion errors. Keep in mind that the signal level the LM95241 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 LM95241.
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 LM95241
pins.
3. Ideally, the LM95241 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 1°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 LM95241's GND pin is as close as possible to the Processor's GND that is
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 LM95241. 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 LM95241'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
Submit Documentation Feedback
Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: LM95241
LM95241
www.ti.com
SNIS143E – AUGUST 2006 – 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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Copyright © 2006–2013, Texas Instruments Incorporated
Product Folder Links: LM95241
23
PACKAGE OPTION ADDENDUM
www.ti.com
23-Sep-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
LM95241CIMM-1
ACTIVE
VSSOP
DGK
8
LM95241CIMM-1/NOPB
ACTIVE
VSSOP
DGK
8
LM95241CIMM-2
ACTIVE
VSSOP
DGK
8
LM95241CIMM-2/NOPB
ACTIVE
VSSOP
DGK
8
LM95241CIMM/NOPB
ACTIVE
VSSOP
DGK
8
LM95241CIMMX
ACTIVE
VSSOP
DGK
LM95241CIMMX-1
ACTIVE
VSSOP
LM95241CIMMX-1/NOPB
ACTIVE
LM95241CIMMX-2
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
T29C
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T29C
TBD
Call TI
Call TI
0 to 85
T30C
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T30C
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T28C
8
TBD
Call TI
Call TI
0 to 85
T28C
DGK
8
TBD
Call TI
Call TI
0 to 85
T29C
VSSOP
DGK
8
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T29C
ACTIVE
VSSOP
DGK
8
TBD
Call TI
Call TI
0 to 85
T30C
LM95241CIMMX-2/NOPB
ACTIVE
VSSOP
DGK
8
3500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T30C
LM95241CIMMX/NOPB
ACTIVE
VSSOP
DGK
8
3500
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
0 to 85
T28C
1000
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.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
23-Sep-2013
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.
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 2
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
LM95241CIMM-1/NOPB
VSSOP
DGK
8
1000
178.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM95241CIMM-2/NOPB
VSSOP
DGK
8
1000
178.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM95241CIMM/NOPB
VSSOP
DGK
8
1000
178.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM95241CIMMX-1/NOPB VSSOP
DGK
8
3500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
LM95241CIMMX-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
LM95241CIMMX/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)
LM95241CIMM-1/NOPB
VSSOP
DGK
8
1000
210.0
185.0
35.0
LM95241CIMM-2/NOPB
VSSOP
DGK
8
1000
210.0
185.0
35.0
LM95241CIMM/NOPB
VSSOP
DGK
8
1000
210.0
185.0
35.0
LM95241CIMMX-1/NOPB
VSSOP
DGK
8
3500
367.0
367.0
35.0
LM95241CIMMX-2/NOPB
VSSOP
DGK
8
3500
367.0
367.0
35.0
LM95241CIMMX/NOPB
VSSOP
DGK
8
3500
367.0
367.0
35.0
Pack Materials-Page 2
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