LM82
Remote Diode and Local Digital Temperature Sensor
with Two-Wire Interface
General Description
The LM82 is a digital temperature sensor with a 2 wire serial
interface that senses the voltage and thus the temperature of
a remote diode using a Delta-Sigma analog-to-digital con-
verter with a digital over-temperature detector. The LM82 ac-
curately senses its own temperature as well as the tempera-
ture of external devices, such as Pentium II
Processors or
diode connected 2N3904s. The temperature of any ASIC
can be detected using the LM82 as long as a dedicated di-
ode (semiconductor junction) is available on the die. Using
the SMBus interface a host can access the LM82's registers
at any time. Activation of a T_CRIT_A output occurs when
any temperature is greater than a programmable comparator
limit, T_CRIT. Activation of an INT output occurs when any
temperature is greater than its corresponding programmable
comparator HIGH limit.
The host can program as well as read back the state of the
T_CRIT register and the 2 T_HIGH registers. Three state
logic inputs allow two pins (ADD0, ADD1) to select up to 9
SMBus address locations for the LM82. The sensor powers
up with default thresholds of 127C for T_CRIT and all
T_HIGHs. The LM82 is pin for pin and register compatible
with the LM84, Maxim MAX1617 and Analog Devices
ADM1021.
Features
n
Accurately senses die temperature of remote ICs, or
diode junctions
n
On-board local temperature sensing
n
SMBus and I
2
C compatible interface, supports
SMBus 1.1 TIMEOUT
n
Two interrupt outputs: INT and T_CRIT_A
n
Register readback capability
n
7 bit plus sign temperature data format, 1 C resolution
n
2 address select pins allow connection of 9 LM82s on a
single bus
Key Specifications
j
Supply Voltage
3.0V to 3.6V
j
Supply Current
0.8mA (max)
j
Local Temp Accuracy (includes quantization error)
0C to +85C
3.0C (max)
j
Remote Diode Temp Accuracy (includes quantization
error)
+25C to +100C
3C (max)
0C to +125C
4C (max)
Applications
n
System Thermal Management
n
Computers
n
Electronic Test Equipment
n
Office Electronics
n
HVAC
Simplified Block Diagram
SMBus
TM
is a trademark of the Intel Corporation.
Pentium II
is a registered trademark of the Intel Corporation.
I2C
is a registered trademark of the Philips Corporation.
DS101297-1
January 2000
LM82
Remote
Diode
and
Local
Digital
T
emperature
Sensor
with
T
wo-W
ire
Interface
2000 National Semiconductor Corporation
DS101297
www.national.com
Connection Diagram
Ordering Information
Order
Number
NS
Package
Number
Transport
Media
LM82CIMQA
MQA16A
(QSOP-16)
95 Units in
Rail
LM82CIMQAX
MQA16A
(QSOP-16)
2500 Units on
Tape and
Reel
Typical Application
QSOP-16
DS101297-2
TOP VIEW
DS101297-3
LM82
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2
Pin Description
Label
Pin #
Function
Typical Connection
NC
1, 5
floating, unconnected
Left floating. PC board traces may be routed
through the pads for these pins. No restrictions
applied.
V
CC
2
Positive Supply Voltage
Input
DC Voltage from 3.0 V to 3.6 V
D+
3
Diode Current Source
To Diode Anode. Connected to remote discrete
diode junction or to the diode junction on a remote
IC whose die temperature is being sensed. When
not used they should be left floating.
D-
4
Diode Return Current
Sink
To Diode Cathode. Must float when not used.
ADD0ADD1
10, 6
User-Set SMBus (I
2
C)
Address Inputs
Ground (Low, "0"), V
CC
(High, "1") or open
("TRI-LEVEL")
GND
7, 8
Power Supply Ground
Ground
NC
9, 13, 15
Manufacturing test pins.
Left floating. PC board traces may be routed
through the pads for these pins, although the
components that drive these traces should share
the same supply as the LM82 so that the Absolute
Maximum Rating, Voltage at Any Pin, is not
violated.
INT
11
Interrupt Output,
open-drain
Pull Up Resistor, Controller Interrupt or Alert Line
SMBData
12
SMBus (I
2
C) Serial
Bi-Directional Data Line,
open-drain output
From and to Controller, Pull-Up Resistor
SMBCLK
14
SMBus (I
2
C) Clock Input
From Controller, Pull-Up Resistor
T_CRIT_A
16
Critical Temperature
Alarm, open-drain output
Pull Up Resistor, Controller Interrupt Line or
System Shutdown
LM82
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3
Absolute Maximum Ratings
(Note 1)
Supply Voltage
-0.3 V to 6.0 V
Voltage at SMBData,
SMBCLK, T_CRIT_A & INT pins
-0.5V to 6V
Voltage at Other Pins
-0.3 V to
(V
CC
+ 0.3 V)
D- Input Current
1 mA
Input Current at All Other Pins (Note
2)
5 mA
Package Input Current (Note 2)
20 mA
SMBData, T_CRIT_A, INT Output
Sink Current
10 mA
Storage Temperature
-65C to +150C
Soldering Information, Lead Temperature
QSOP Package (Note 3)
Vapor Phase (60 seconds)
215C
Infrared (15 seconds)
220C
ESD Susceptibility (Note 4)
Human Body Model
2000 V
Machine Model
250 V
Operating Ratings
(Notes 1, 5)
Specified Temperature Range
T
MIN
to T
MAX
LM82
-40C to +125C
Supply Voltage Range (V
CC
)
+3.0V to +3.6V
Temperature-to-Digital Converter Characteristics
Unless otherwise noted, these specifications apply for V
CC
=+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.
Parameter
Conditions
Typical
Limits
Units
(Note 6)
(Note 7)
(Limit)
Temperature Error using Local
Diode ((Note 8))
T
A
= 0 C to +85C,
V
CC
=+3.3V
1
3
C (max)
T
A
= -40 C to +125C,
V
CC
=+3.3V
4
C (max)
Temperature Error using Remote
Diode ((Note 8))
T
A
= +60 C to +100C,
V
CC
=+3.3V
3
C (max)
T
A
= 0 C to +100C,
V
CC
=+3.3V
3
C (max)
T
A
= 0 C to +125C,
V
CC
=+3.3V
4
C (max)
Resolution
8
Bits
1
C
Conversion Time of All
Temperatures
(Note 10)
460
600
ms (max)
Quiescent Current (Note 9)
SMBus (I
2
C) Inactive
0.500
0.80
mA (max)
D- Source Voltage
0.7
V
Diode Source Current
(D+ - D-)=+ 0.65V; high
level
125
A (max)
60
A (min)
Low level
15
A (max)
5
A (min)
T_CRIT_A and INT Output
Saturation Voltage
I
OUT
= 3.0 mA
0.4
V (max)
Power-On Reset Threshold
On V
CC
input, falling
edge
2.3
1.8
V (max)
V (min)
Local and Remote T_CRIT and
HIGH Default Temperature settings
(Note 11)
+127
C
LM82
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Logic Electrical Characteristics
DIGITAL DC CHARACTERISTICS
Unless otherwise noted, these specifications apply for V
CC
=+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)
SMBData, SMBCLK
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)
SMBData and SMBCLK Digital
Input Hysteresis
300
mV
I
IN(1)
Logical "1" Input Current
V
IN
= V
CC
0.005
1.5
A (max)
I
IN(0)
Logical "0" Input Current
V
IN
= 0 V
-0.005
1.5
A (max)
ADD0, ADD1
V
IN(1)
Logical "1" Input Voltage
V
CC
1.5
V (min)
V
IN(0)
Logical "0"Input Voltage
GND
0.6
V (max)
I
IN(1)
Logical "1" Input Current
V
IN
= V
CC
2
A (max)
I
IN(0)
Logical "0" Input Current
V
IN
= 0 V
-2
A (max)
ALL DIGITAL INPUTS
C
IN
Input Capacitance
20
pF
ALL DIGITAL OUTPUTS
I
OH
High Level Output Current
V
OH
= V
CC
100
A (max)
V
OL
SMBus Low Level Output
Voltage
I
OL
= 3 mA
I
OL
= 6 mA
0.4
0.6
V (max)
LM82
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