LM95231
Precision Dual Remote Diode Temperature Sensor with
SMBus Interface and TruTherm
TM
Technology
General Description
The LM95231 is a precision dual remote diode temperature
sensor (RDTS) that uses National's 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-to-processor non-ideality spread. The diode con-
nected 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 11-bits signed or un-
signed with the digital filtering disabled. When the filtering is
enabled the resolution increases to 13-bits signed or un-
signed. In the unsigned mode the LM95231 remote diode
readings can resolve temperatures above 127C. Local tem-
perature readings have a resolution of 9-bits plus sign.
Features
n
Accurately senses die temperature of remote ICs or
diode junctions
n
Uses TruTherm technology for precision "thermal diode"
temperature measurement
n
Thermal diode input stage with analog filtering
n
Thermal diode digital filtering
n
Intel Pentium 4 processor on 90nm process or 2N3904
non-ideality selection
n
Remote diode fault detection
n
On-board local temperature sensing
n
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
n
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
n
Local temperature readings:
-- 0.25 C
-- 9-bits plus sign
n
Status register support
n
Programmable conversion rate allows user optimization
of power consumption
n
Shutdown mode one-shot conversion control
n
SMBus 2.0 compatible interface, supports TIMEOUT
n
8-pin MSOP package
Key Specifications
j
Remote Temperature Accuracy
0.75C (max)
j
Local Temperature Accuracy
3.0C (max)
j
Supply Voltage
3.0V to 3.6V
j
Supply Current
363A (typ)
Applications
n
Processor/Computer System Thermal Management
(e.g. Laptop, Desktop, Workstations, Server)
n
Electronic Test Equipment
n
Office Electronics
Connection Diagram
MSOP-8
20120202
TOP VIEW
TruTherm
TM
is a trademark of National Semiconductor Corporation.
I2C
is a registered trademark of Philips Corporation.
Pentium
is a registered trademark of Intel Corporation.
January 2006
LM95231
Precision
Dual
Remote
Diode
T
emperature
Sensor
with
SMBus
Interface
and
T
ruTherm
T
echnology
2006 National Semiconductor Corporation
DS201202
www.national.com
Ordering Information
Part Number
Package
Marking
NS Package
Number
Transport
Media
SMBus Device
Address
Thermal Diode
Accuracy
LM95231BIMM*
T23B
MUA08A (MSOP-8)
1000 Units on Tape
and Reel
010 1011
0.75
LM95231BIMMX*
T23B
MUA08A (MSOP-8)
3500 Units on Tape
and Reel
010 1011
0.75
LM95231BIMM-1*
T25B
MUA08A (MSOP-8)
1000 Units on Tape
and Reel
001 1001
0.75
LM95231BIMMX-1*
T25B
MUA08A (MSOP-8)
3500 Units on Tape
and Reel
001 1001
0.75
LM95231BIMM-2*
T26B
MUA08A (MSOP-8)
1000 Units on Tape
and Reel
010 1010
0.75
LM95231BIMMX-2*
T26B
MUA08A (MSOP-8)
3500 Units on Tape
and Reel
010 1010
0.75
LM95231CIMM
T23C
MUA08A (MSOP-8)
1000 Units on Tape
and Reel
010 1011
1.25
LM95231CIMMX
T23C
MUA08A (MSOP-8)
3500 Units on Tape
and Reel
010 1011
1.25
LM95231CIMM-1
T25C
MUA08A (MSOP-8)
1000 Units on Tape
and Reel
001 1001
1.25
LM95231CIMMX-1
T25C
MUA08A (MSOP-8)
3500 Units on Tape
and Reel
001 1001
1.25
LM95231CIMM-2
T26C
MUA08A (MSOP-8)
1000 Units on Tape
and Reel
010 1010
1.25
LM95231CIMMX-2
T26C
MUA08A (MSOP-8)
3500 Units on Tape
and Reel
010 1010
1.25
* Not released to production yet.
Typical Application
20120203
Pin Descriptions
Label
Pin #
Function
Typical Connection
D1+
1
Diode Current Source
To Diode Anode. Connected to remote discrete
diode-connected transistor junction or to the
diode-connected transistor junction on a remote IC
whose die temperature is being sensed. A capacitor
is not required between D1+ and D1-. A 100 pF
capacitor between D1+ and D1- can be added and
may improve performance in noisy systems.
LM95231
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2
Pin Descriptions
(Continued)
Label
Pin #
Function
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
diode-connected transistor junction or to the
diode-connected transistor junction on a remote IC
whose die temperature is being sensed. A capacitor
is not required between D2+ and D2-. A 100 pF
capacitor between D2+ and D2- can be added and
may improve performance in noisy systems.
D2-
4
Diode Return Current Sink
To Diode Cathode. A capacitor is not required
between D2+ and D2-. A 100 pF capacitor between
D2+ and D2- can be added and may improve
performance in noisy systems.
GND
5
Power Supply Ground
System low noise ground
V
DD
6
Positive Supply Voltage
Input
DC Voltage from 3.0 V to 3.6 V. V
DD
should be
bypassed with a 0.1 F 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 F capacitor
may be required to achieve this.
SMBDAT
7
SMBus Bi-Directional Data
Line, Open-Drain Output
From and to Controller; may require an external
pull-up resistor
SMBCLK
8
SMBus Clock Input
From Controller; may require an external pull-up
resistor
Simplified Block Diagram
20120201
LM95231
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3
Absolute Maximum Ratings
(Note 1)
Supply Voltage
-0.3 V to 6.0 V
Voltage at SMBDAT, SMBCLK
-0.5V to 6.0V
Voltage at Other Pins
-0.3 V to (V
DD
+ 0.3 V)
Input Current at All Pins (Note 2)
5 mA
Package Input Current (Note 2)
30 mA
SMBDAT Output Sink Current
10 mA
Junction Tempeature (Note 3)
125C
Storage Temperature
-65C to +150C
ESD Susceptibility (Note 4)
Human Body Model
2000 V
Machine Model
200 V
Soldering process must comply with National's reflow
temperature profile specifications. Refer to
http://www.national.com/packaging/. (Note 5)
Operating Ratings
(Notes 1, 3)
Operating Temperature Range
0C to +125C
Electrical Characteristics
Temperature Range
T
MIN
T
A
T
MAX
LM95231BIMM, LM95231CIMM
0C
T
A
+85C
Supply Voltage Range (V
DD
)
+3.0V to +3.6V
Temperature-to-Digital Converter Characteristics
Unless otherwise noted, these specifications apply for V
DD
=+3.0Vdc to 3.6Vdc. Boldface limits apply for T
A
= T
J
=
T
MIN
T
A
T
MAX
; all other limits T
A
= T
J
=+25C, unless otherwise noted. T
J
is the junction temperature of the LM95231. T
D
is the
junction temperature of the remote thermal diode.
Parameter
Conditions
Typical
LM95231
BIMM
LM95231
CIMM
Units
(Note 6)
Limits
(Note 7)
Limits
(Note 7)
(Limit)
Accuracy Using Local Diode
T
A
= 0C to +85C, (Note 8)
1
3
3
C (max)
Accuracy Using Remote Diode, see (Note 9)
for Thermal Diode Processor Type.
T
A
= +20C to
+40C
T
D
= +45C
to +85C
1.25
C (max)
T
A
= TBD
T
D
= TBD
0.75
C (max)
T
A
= +0C to
+85C
T
D
= +25C
to +140C
2
2.5
C (max)
Remote Diode Measurement Resolution with
filtering turned off
10+sign/11
Bits
0.125
C
Remote Diode Measurement Resolution with
digital filtering turned on
12+sign/13
Bits
0.03125
C
Local Diode Measurement Resolution
9+sign
Bits
0.25
C
Conversion Time of All Temperatures at the
Fastest Setting
(Note 11) TruTherm Mode
Disabled
66
73
73
ms (max)
TruTherm Mode enabled
67.5
74.6
74.6
ms (max)
Average Quiescent Current (Note 10)
SMBus Inactive, 1 Hz
conversion rate
367
521
521
A (max)
Shutdown
272
A
D- Source Voltage
0.4
V
Diode Source Current Ratio
16
Diode Source Current
(V
D+
- V
D-
) = + 0.65V;
high-level
176
300
300
A (max)
100
100
A (min)
Low-level
11
A
Power-On Reset Threshold
Measure on V
DD
input, falling
edge
2.7
1.8
2.7
1.8
V (max)
V (min)
LM95231
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4
Logic Electrical Characteristics
Digital DC Characteristics
Unless otherwise noted, these specifications apply for V
DD
=+3.0 to 3.6 Vdc. Boldface limits apply for T
A
= T
J
= T
MIN
to
T
MAX
; all other limits T
A
= T
J
=+25C, unless otherwise noted.
Symbol
Parameter
Conditions
Typical
Limits
Units
(Note 6)
(Note 7)
(Limit)
SMBDAT, SMBCLK INPUTS
V
IN(1)
Logical "1" Input Voltage
2.1
V (min)
V
IN(0)
Logical "0"Input Voltage
0.8
V (max)
V
IN(HYST)
SMBDAT and SMBCLK Digital Input
Hysteresis
400
mV
I
IN(1)
Logical "1" Input Current
V
IN
= V
DD
0.005
10
A (max)
I
IN(0)
Logical "0" Input Current
V
IN
= 0 V
-0.005
10
A (max)
C
IN
Input Capacitance
5
pF
SMBDAT OUTPUT
I
OH
High Level Output Current
V
OH
= V
DD
10
A (max)
V
OL
SMBus Low Level Output Voltage
I
OL
= 4mA
I
OL
= 6mA
0.4
0.6
V (max)
SMBus Digital Switching Characteristics
Unless otherwise noted, these specifications apply for V
DD
=+3.0 Vdc to +3.6 Vdc, C
L
(load capacitance) on output lines = 80
pF. Boldface limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other limits T
A
= T
J
= +25C, unless otherwise noted. The switching
characteristics of the LM95231 fully meet or exceed the published specifications of the SMBus version 2.0. The following pa-
rameters are the timing relationships between SMBCLK and SMBDAT signals related to the LM95231. They adhere to but are
not necessarily the SMBus bus specifications.
Symbol
Parameter
Conditions
Typical
Limits
Units
(Note 6)
(Note 7)
(Limit)
f
SMB
SMBus Clock Frequency
100
10
kHz (max)
kHz (min)
t
LOW
SMBus Clock Low Time
from V
IN(0)
max to V
IN(0)
max
4.7
25
s (min)
ms (max)
t
HIGH
SMBus Clock High Time
from V
IN(1)
min to V
IN(1)
min
4.0
s (min)
t
R,SMB
SMBus Rise Time
(Note 12)
1
s (max)
t
F,SMB
SMBus Fall Time
(Note 13)
0.3
s (max)
t
OF
Output Fall Time
C
L
= 400pF,
I
O
= 3mA, (Note 13)
250
ns (max)
t
TIMEOUT
SMBDAT and SMBCLK Time Low for Reset of
Serial Interface (Note 14)
25
35
ms (min)
ms (max)
t
SU;DAT
Data In Setup Time to SMBCLK High
250
ns (min)
t
HD;DAT
Data Out Stable after SMBCLK Low
300
1075
ns (min)
ns (max)
t
HD;STA
Start Condition SMBDAT Low to SMBCLK
Low (Start condition hold before the first clock
falling edge)
100
ns (min)
t
SU;STO
Stop Condition SMBCLK High to SMBDAT
Low (Stop Condition Setup)
100
ns (min)
t
SU;STA
SMBus Repeated Start-Condition Setup Time,
SMBCLK High to SMBDAT Low
0.6
s (min)
t
BUF
SMBus Free Time Between Stop and Start
Conditions
1.3
s (min)
LM95231
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5
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