LM95235
Precision Remote Diode Temperature Sensor with
SMBus Interface and TruTherm
TM
Technology
General Description
The LM95235 is an 11-bit digital temperature sensor with a
2-wire System Management Bus (SMBus) interface and Tru-
Therm technology that can monitor the temperature of a
remote diode as well as its own temperature. The LM95235
can be used to very accurately monitor the temperature of
external devices such as microprocessors, graphics proces-
sors, or a diode-connected MMBT3904 transistor. TruTherm
technology allows the LM95235 to precisely monitor thermal
diodes found in 90 nm and smaller geometry processes.
LM95235 reports temperature in two different formats for
+127.875C/-128C range and 0C/255C range. The
LM95235 T_CRIT and OS outputs are asserted when either
unmasked channel exceeds its programmed limit and can be
used to shutdown the system, to turn on the system fans, or
as a microcontroller interrupt function. The current status of
the T_CRIT and OS pins can be read back from the status
registers via the SMBus interface. All limits have a shared
programmable hysteresis register.
The remote temperature channel of the LM95235 has a
programmable digital filter. The LM95235 contains a diode
model selection bit to select between a typical Intel
proces-
sor on a 65 nm or 90 nm process or MMBT3904, as well as
an offset register for maximum flexibility and best accuracy.
The LM95235 has a three-level address pin to connect up to
3 devices to the same SMBus master, that is shared with the
OS output. The LM95235 has a programmable conversion
rate register and a standby mode to save power. One con-
version can be triggered in standby mode by writing to the
one-shot register.
Features
n
Remote and Local temperature channels
n
Diode Model Selection Bit - MMBT3904 or 65/90 nm
processor diodes
n
Two Formats: -128C to +127.875C and 0C to
255.875C
n
Digital filter for remote channel
n
Programmable TCRIT and OS thresholds
n
Programmable shared hysteresis register
n
Diode Fault Detection
n
Mask, Offset, and Status Registers
n
SMBus 2.0 compatible interface, supports TIMEOUT
n
Programmable conversion rate for best power
consumption
n
Three-level address pin
n
Standby mode one-shot conversion control
n
Pin-for-pin compatible with the LM86/LM89
n
8-pin MSOP package
Key Specifications
j
Supply Voltage
3.0 V to 3.6 V
j
Supply Current, Conv. Rate = 1 Hz
350 A (typ)
j
Remote Diode Temperature Accuracy
T
A
= 25C to 85C; T
D
= 60C to 100C
0.75C (max)
T
A
= 25C to 85C; T
D
= 40C to 125C
1.5C (max)
j
Local Temperature Accuracy
T
A
= 25C to 100C
2.0C (max)
j
Conversion Rate, Both Channels
16 to 0.4 Hz
Applications
n
Processor/Computer System Thermal Management
(e.g. Laptops, Desktops, Workstations, Servers)
n
Electronic Test Equipment
n
Office Electronics
Connection Diagram
MSOP-8
20174902
TOP VIEW
TruTherm
TM
is a trademark of National Semiconductor Corporation.
Intel
is a registered trademark of Intel Corporation.
Pentium
is a registered trademark of Intel Corporation.
Intel
Core
TM
Duo is a trademark of Intel Corporation.
Intel
Core
TM
Solo is a trademark of Intel Corporation.
June 2006
LM95235
Precision
Remote
Diode
T
emperature
Sensor
with
SMBus
Interface
and
T
ruTherm
T
echnology
2006 National Semiconductor Corporation
DS201749
www.national.com
Ordering Information
Order Code
Package
Marking
NS Package
Number
Transport Media
Features
LM95235CIMM
T36C
MUA08A
(MSOP-8)
1000 Units on Tape and Reel
T
A
= 25C to 85C
LM95235CIMMX
T36C
MUA08A
(MSOP-8)
3500 Units on Tape and Reel
T
A
= 25C to 85C
LM95235DIMM
T36D
MUA08A
(MSOP-8)
1000 Units on Tape and Reel
T
A
= -40C to 85C, T
D
= -40C
to 125C
LM95235DIMMX
T36D
MUA08A
(MSOP-8)
3500 Units on Tape and Reel
T
A
= -40C to 85C, T
D
= -40C
to 125C
LM95235EIMM
T36E
MUA08A
(MSOP-8)
1000 Units on Tape and Reel
T
A
= -40C to 85C, T
D
= -40C
to 125C, 3904 only
LM95235EIMMX
T36E
MUA08A
(MSOP-8)
3500 Units on Tape and Reel
T
A
= -40C to 85C, T
D
= -40C
to 125C, 3904 only
Simplified Block Diagram
20174901
LM95235
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2
Pin Descriptions
Pin
Number
Name
Type
Function and Connection
1
V
DD
Power
Device power supply. Requires bypass capacitor of 10 F in parallel with
0.1 F and 100 pF. Place 100 pF closest to device pin.
2
D+
Analog Input/Output
Positive input from the thermal diode.
3
D-
Analog Input/Output
Negative input from the thermal diode.
4
T_CRIT
Digital Output
Critical temperature output. Open-drain output requires pull-up resistor.
Active "LOW".
5
GND
Ground
Device ground.
6
OS/A0
Digital Input/Output
Over-temperature shutdown comparator output or SMBus slave address
input. Defaults as an SMBus slave address input that selects one of
three addresses. Can be tied to V
DD
, GND, or to the middle of a resistor
divider connected between V
DD
and GND. When programmed as an OS
comparator output it is active "Low" and open drain.
7
SMBDAT
Digital Input/Output
SMBus interface data pin. Open-drain output requires pull-up resistor.
8
SMBCLK
Digital Input
SMBus interface clock pin.
Typical Application
20174903
LM95235
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3
Absolute Maximum Ratings
(Note 1)
Supply Voltage, V
DD
-0.3V to 6.0V
Voltage at SMBDAT, SMBCLK,
-0.5V to 6.0V
T_CRIT, OS/A0 Pins
Voltage at Other Pins
(V
DD
+0.3V)
Input Current at D- Pin (Note 4)
1 mA
Input Current at All Other Pins
(Note 4)
5 mA
Output Sink Current
SMBDAT, T_Crit, OS Pins
10 mA
Package Input Current (Note 4)
30 mA
ESD Susceptibility (Note 3)
Human Body Model
Machine Model
Charged Device Model
2500V
250V
1000V
Junction Temperature (Note 2)
+125C
Storage Temperature
-65C to +150C
Operating Ratings
(Note 1)
Operating Temperature Range
-40C to +125C
Electrical Characteristics
Temperature Range
T
MIN
T
A
T
MAX
LM95235CIMM
0C
T
A
+85C
LM95235DIMM
-40C
T
A
+85C
LM95235EIMM
-40C
T
A
+85C
Supply Voltage (V
DD
)
+3.0V to +3.6V
Soldering process must comply with National Semiconduc-
tor's Reflow Temperature Profile specifications. Refer to
www.national.com/packaging. (Note 5)
Temperature-to-Digital Converter Characteristics
Unless otherwise noted, these specifications apply for V
DD
= +3.0 Vdc to 3.6 Vdc. 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 LM95235. T
D
is the junction temperature of the remote thermal diode.
Parameter
Conditions
Typical
(Note 6)
LM95235
CIMM
Limits
(Note 7)
LM95235
DIMM
Limits
(Note 7)
LM95235
EIMM
Limits
(Note 7)
Units
Temperature Accuracy
Using Local Diode (Note 8)
T
A
= 25C to +100C
1
2
2
2
C (max)
T
A
= -40C to +25C
6.0
6.0
C (max)
Temperature Accuracy
Using Remote Diode
(Note 9)
T
A
= +25C to +85C;
T
D
= +60C to +100C
65nm Intel
Processor
0.5
0.75
0.75
0.75
C (max)
T
A
= +25C to +85C;
T
D
= +60C to +100C
MMBT3904
0.5
1.0
1.0
1.0
C (max)
T
A
= +25C to +85C;
T
D
= +40C to +120C
MMBT3904 or
65nm Intel
Processor
0.75
1.5
1.5
1.5
C (max)
T
A
= -40C to +25C;
T
D
= +25C to +125C
MMBT3904 or
65nm Intel
Processor
3.0
C (max)
T
A
= -40C to +25C;
T
D
= +25C to +125C
MMBT3904
3.0
C (max)
T
A
= -40C to +25C;
T
D
= -40C to +25C
MMBT3904
5.0
5.0
C (max)
Remote Diode
Measurement Resolution
Digital Filter Off
11
Bits
0.125
C
Digital Filter On
13
Bits
0.03125
C
Local Diode Measurement
Resolution
11
Bits
0.125
C
Conversion Time, Fastest
Setting (Note 10)
Local and Remote Channels
63
72
72
72
ms (max)
Local or Remote Channels
33
ms
Quiescent Current
SMBus Inactive, 1 Hz conversion rate
(Note 11)
350
650
650
650
A (max)
Standby Mode
300
A
LM95235
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4
Temperature-to-Digital Converter Characteristics
(Continued)
Unless otherwise noted, these specifications apply for V
DD
= +3.0 Vdc to 3.6 Vdc. 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 LM95235. T
D
is the junction temperature of the remote thermal diode.
Parameter
Conditions
Typical
(Note 6)
LM95235
CIMM
Limits
(Note 7)
LM95235
DIMM
Limits
(Note 7)
LM95235
EIMM
Limits
(Note 7)
Units
D- Source Voltage
400
mV
External Diode Current
Source
High-level
172
225
225
225
A (max)
Low-level
10.75
A
Diode Source Current Ratio
16
Power-On Reset Voltage
2.8
2.8
2.8
V (max)
1.6
1.6
1.6
V (min)
T_CRIT Pin Temperature
Threshold
Default
+110
C
OS Pin Temperature
Threshold
Default
+85
C
Logic Electrical Characteristics
Digital DC Characteristics
Unless otherwise noted, these specifications apply for V
DD
= +3.0 Vdc 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
A0 DIGITAL INPUT
V
IH
Input High Voltage
0.90 x V
DD
V (min)
V
IM
Input Middle Voltage
0.57 x V
DD
V (max)
0.43 x V
DD
V (min)
V
IL
Input Low Voltage
0.10 x V
DD
V (max)
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, T_CRIT, OS DIGITAL OUTPUTS
I
OH
High Level Output Leakage Current
V
OUT
= V
DD
10
A (max)
V
OL(T_CRIT, OS)
T_CRIT, OS Low Level Output Voltage
I
OL
= 6 mA
0.4
V (max)
V
OL(SMBDAT)
SMBDAT Low Level Output Voltage
I
OL
= 4 mA
I
OL
= 6 mA
0.4
0.6
V (max)
V (max)
C
OUT
Digital Output Capacitance
5
pF
LM95235
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