LM76
0.5C,
1C, 12-Bit + Sign Digital Temperature Sensor
and Thermal Window Comparator with Two-Wire
Interface
General Description
The LM76 is a digital temperature sensor and thermal win-
dow comparator with an I
2
C
TM
Serial Bus interface with an
accuracy of
1C. This accuracy for the LM76CHM is speci-
fied for a -10C to 45C temperature range, while for the
LM76CNM the temperature range is 70C to 100C. The
LM76CHM is specified with an accuracy
0.5C at 25C. The
window-comparator architecture of the LM76 eases the de-
sign of temperature control systems conforming to the ACPI
(Advanced Configuration and Power Interface) specification
for personal computers. The open-drain Interrupt (INT) out-
put becomes active whenever temperature goes outside a
programmable window, while a separate Critical Tempera-
ture Alarm (T_CRIT_A) output becomes active when the
temperature exceeds a programmable critical limit. The INT
output can operate in either a comparator or event mode,
while the T_CRIT_A output operates in comparator mode
only.
The host can program both the upper and lower limits of the
window as well as the critical temperature limit. Program-
mable hysterisis as well as a fault queue are available to
minimize false tripping. Two pins (A0, A1) are available for
address selection. The sensor powers up with default thresh-
olds of 2C T
HYST
, 10C T
LOW
, 64C T
HIGH
, and 80C
T_CRIT.
The LM76's 3.3V and 5.0V supply voltage, Serial Bus inter-
face, 12-bit + sign output, and full-scale range of over 127C
make it ideal for a wide range of applications. These include
thermal management and protection applications in personal
computers, electronic test equipment, office electronics and
bio-medical applications.
Features
n
Window comparison simplifies design of ACPI
compatible temperature monitoring and control.
n
Serial Bus interface
n
Separate open-drain outputs for Interrupt and Critical
Temperature shutdown
n
Shutdown mode to minimize power consumption
n
Up to 4 LM76s can be connected to a single bus
n
12-bit + sign output; full-scale reading of over 127C
Key Specifications
n
Supply Voltage
3.3V or 5.0V
n
Supply Current
operating
250 A (typ)
450 A (max)
shutdown
8 A (max)
n
Temperature
Accuracy
+25C
-10C to +45C
0.5C(max)
1.0C(max)
70C to 100C
1.0C(max)
n
Resolution
0.0625C
Applications
n
System Thermal Management
n
Personal Computers
n
Office Electronics
n
HVAC
I2C
is a registered trademark of Philips Corporation.
January 2000
LM76
0.5C,
1C,
12-Bit
+
Sign
Digital
T
emperature
Sensor
and
Thermal
W
indow
Comparator
with
T
wo-W
ire
Interface
2000 National Semiconductor Corporation
DS101015
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Simplified Block Diagram
Connection Diagram
Ordering Information
Order Number
Supply Voltage
Acurracy
Temperature
Range for
Accuracy
Transport Media
LM76CHM-5
5.0V
0.5C
1.0C
25C
-10C to 45C
95 units in Rail
LM76CHMX-5
5.0V
0.5C
1.0C
25C
-10C to 45C
2500 Units on Tape and
Reel
LM76CNM-3
3.3V
1C
70C to 100C
95 units in Rail
LM76CNMX-3
3.3V
1C
70C to 100C
2500 Units on Tape and
Reel
Pin Description
Label
Pin #
Function
Typical Connection
SDA
1
Serial Bi-Directional Data Line, Open Drain Output,
CMOS Logic Level
Pull Up Resistor, Controller I
2
C Data Line
SCL
2
Serial Bus Clock Input, CMOS Logic Level
From Controller I
2
C Clock Line
T_CRIT_A
3
Critical Temperature Alarm, Open Drain Output
Pull Up Resistor, Controller Interrupt Line
or System Hardware Shutdown
GND
4
Power Supply Ground
Ground
INT
5
Interrupt, Open Drain Output
Pull Up Resistor, Controller Interrupt Line
+V
S
8
Positive Supply Voltage Input
DC Voltage from 3.3V power supply or
5V.
A0A1
7,6
User-Set Address Inputs, TTL Logic Level
Ground (Low, "0") or +V
S
(High, "1")
DS101015-1
SO-8
DS101015-2
LM76 See NS Package Number M08A
LM76
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2
Pin Description
(Continued)
DS101015-3
FIGURE 1. Typical Application
LM76
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3
Absolute Maximum Ratings
(Note 1)
Supply Voltage
-0.3V to 6.5V
Voltage at any Pin
-0.3V to (+V
S
+ 0.3V)
Input Current at any Pin
5mA
Package Input Current (Note 2)
20mA
T_CRIT_A and INT Output Sink
Current
10mA
T_CRIT_A and INT Output
Voltage
6.5V
Storage Temperature
-65C to +125C
Soldering Information, Lead
Temperature
SOP Package (Note 3)
Vapor Phase (60 seconds)
215C
Infrared (15 seconds)
220C
ESD Susceptibility (Note 4)
Human Body Model
3000V
Machine Model
250V
Operating Ratings
(Notes 1, 5)
Operating Temperature Range
-55C to +150C
Specified Temperature Range
(Note 6)
T
MIN
to T
MAX
LM76CHM-5
-20C to +85C
LM76CNM-3
-55C to +125C
Supply Voltage Range (+V
S
)(Note 7)
+3.0V to +5.5V
Temperature-to-Digital Converter Characteristics
Unless otherwise noted, these specifications apply for +V
S
=+3.3 Vdc
5% for the LM76CNM-3 and for +V
S
=+5.0 Vdc
10%
for the LM76CHM-5. (Note 7). Boldface limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other limits T
A
= T
J
=+25C, unless oth-
erwise noted.
Parameter
Conditions
Typical
(Note 8)
LM76CNM-3
Limits
(Note 9)
LM76CHM-5
Limits
(Note 9)
Units
(Limit)
Accuracy (Note 7)
T
A
= -25C to +125C for
LM76CNM-3
2.5
C (max)
T
A
= +70C to +100C
1.0
T
A
= -20C to +85C for
LM76CHM-5
1.5
T
A
= -10C to +45C
1.0
T
A
= +25C
0.5
Resolution
(Note 10)
13
0.0625
Bits
C
Temperature Conversion
Time
(Note 11)
400
500
1000
ms
Quiescent Current
I
2
C Inactive
0.25
mA
I
2
C Active
0.25
0.5
0.45
mA (max)
Shutdown Mode:
5
A
12
18
A (max)
T
A
=+85C
8
A (max)
T
A
=+25C
12
A (max)
T
HYST
Default Temperature
(Notes 13, 14)
2
C
T
LOW
Default Temperature
(Note 14)
10
C
T
HIGH
Default Temperature
(Note 14)
64
C
T
CRIT
Default Temperature
(Note 14)
80
C
Logic Electrical Characteristics
DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for for +V
S
=+3.3 Vdc
5% for the
LM76CNM-3 and for +V
S
=+5.0 Vdc
10% for the LM76CHM-5. . 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
(Note 8)
Limits
(Note 9)
Units
(Limit)
V
IN(1)
SDA and SCL Logical "1" Input
Voltage
+V
S
x 0.7
V (min)
+V
S
+0.3
V (max)
LM76
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4
Logic Electrical Characteristics
(Continued)
DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for for +V
S
=+3.3 Vdc
5% for the
LM76CNM-3 and for +V
S
=+5.0 Vdc
10% for the LM76CHM-5. . 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
(Note 8)
Limits
(Note 9)
Units
(Limit)
V
IN(0)
SDA and SCL Logical "0" Input
Voltage
-0.3
V (min)
+V
S
x 0.3
V (max)
V
IN(HYST)
SDA and SCL Digital Input
Hysteresis
500
250
mV (min)
V
IN(1)
A0 and A1 Logical "1" Input
Voltage
2.0
V (min)
+V
S
+0.3
V (max)
V
IN(0)
A0 and A1 Logical "0" Input
Voltage
-0.3
V (min)
0.8
V (max)
I
IN(1)
Logical "1" Input Current
V
IN
= + V
S
0.005
1.0
A (max)
I
IN(0)
Logical "0" Input Current
V
IN
= 0V
-0.005
-1.0
A (max)
C
IN
Capacitance of All Digital Inputs
20
pF
I
OH
High Level Output Current
V
OH
= + V
S
10
A (max)
V
OL
Low Level Output Voltage
I
OL
= 3 mA
0.4
V (max)
T_CRIT_A Output Saturation
Voltage
I
OUT
= 4.0 mA
(Note 12)
0.8
V (max)
T_CRIT_A Delay
1
Conversions
(max)
t
OF
Output Fall Time
C
L
= 400 pF
250
ns (max)
I
O
= 3 mA
SERIAL BUS DIGITAL SWITCHING CHARACTERISTICS Unless otherwise noted, these specifications apply for +V
S
=+3.3
Vdc
5% for the LM76CNM-3 and for +V
S
=+5.0 Vdc
10% for the LM76CHM-5, CL (load capacitance) on output lines = 80
pF unless otherwise specified. Boldface limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other limits T
A
= T
J
= +25C, unless oth-
erwise noted.
The switching characteristics of the LM76 fully meet or exceed the published specifications of the I
2
C bus. The following pa-
rameters are the timing relationship between SCL and SDA signal related to the LM76. They are not the I
2
C bus specifica-
tions.
Symbol
Parameter
Conditions
Typical
(Note 8)
Limits
(Note 9)
Units
(Limit)
t
1
SCL (Clock) Period
2.5
s(min)
t
2
Data in Set-Up Time to SCL High
100
ns(min)
t
3
Data Out Stable after SCL Low
0
ns(min)
t
4
SDA Low Set-Up Time to SCL Low (Start Condition)
100
ns(min)
t
5
SDA High Hold Time after SCL High (Stop Condition)
100
ns(min)
DS101015-4
LM76
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