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 255C
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 120C
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.
May 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
LM95235CIMM
T36C
MUA08A (MSOP-8)
1000 Units on Tape and Reel
LM95235CIMMX
T36C
MUA08A (MSOP-8)
3500 Units on Tape and Reel
Simplified Block Diagram
20174901
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.
LM95235
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2
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
0C to +125C
Electrical Characteristics
Temperature Range
T
MIN
T
A
T
MAX
LM95235CIMM
0C
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)
Limits
(Note 7)
Units
Temperature Accuracy Using Local
Diode (Note 8)
T
A
= 25C to +100C
1
2
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
C (max)
T
A
= +25C to +85C;
T
D
= +60C to +100C
MMBT3904
0.5
1.0
C (max)
T
A
= +25C to +85C;
T
D
= +40C to +120C
MMBT3904 or
65nm Intel Processor
0.75
1.5
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
ms (max)
Local or Remote Channels
33
ms
Quiescent Current
SMBus Inactive, 1 Hz conversion rate
(Note 11)
350
650
A (max)
Standby Mode
300
A
D- Source Voltage
400
mV
External Diode Current Source
High-level
172
225
A (max)
Low-level
10.75
A
Diode Source Current Ratio
16
Power-On Reset Voltage
2.8
V (max)
1.6
V (min)
T_CRIT Pin Temperature Threshold
Default
+110
C
OS Pin Temperature Threshold
Default
+85
C
LM95235
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4
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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