LM77
9-Bit + Sign Digital Temperature Sensor and Thermal
Window Comparator with Two-Wire Interface
General Description
The LM77 is a digital temperature sensor and thermal win-
dow comparator with an I
2
C
TM
Serial Bus interface. The
window-comparator architecture of the LM77 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 LM77's 3.0V to 5.5V supply voltage range, Serial Bus
interface, 9-bit + sign output, and full-scale range of over
128C make it ideal for a wide range of applications. These
include thermal management and protection applications in
personal computers, electronic test equipment, office elec-
tronics, automotive, and HVAC 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 LM77s can be connected to a single bus
n
9-bit + sign output; full-scale reading of over 128C
n
SOP and MSOP 8-lead packages
Key Specifications
j
Supply Voltage
3.0V to 5.5V
j
Supply Current
operating
250 A (typ)
500 A (max)
shutdown
5 A (typ)
j
Temperature
Accuracy
-10C to 65C
1.5C(max)
-25C to 100C
2C(max)
-55C to 125C
3C(max)
Applications
n
System Thermal Management
n
Personal Computers
n
Office Electronics
n
Electronic Test Equipment
n
Automotive
n
HVAC
I2C
is a registered trademark of Philips Corporation.
July 2001
LM77
9-Bit
+
Sign
Digital
T
emperature
Sensor
and
Thermal
W
indow
Comparator
with
T
wo-W
ire
Interface
2001 National Semiconductor Corporation
DS100136
www.national.com
Simplified Block Diagram
Connection Diagram
Ordering Information
Order Number
Supply Voltage
Package
Supplied In
LM77CIM-3
3.3V
SOP8, M08A
Rail
LM77CIMX-3
3.3V
SOP8, M08A
2500 Units on Tape and Reel
LM77CIM-5
5V
SOP8, M08A
Rail
LM77CIMX-5
5V
SOP8, M08A
2500 Units on Tape and Reel
LM77CIMM-3
3.3V
MSOP8,
MUA08A
Rail
LM77CIMMX-3
3.3V
MSOP8,
MUA08A
3500 Units on Tape and Reel
LM77CIMM-5
5V
MSOP8,
MUA08A
Rail
LM77CIMMX-5
5V
MSOP8,
MUA08A
3500 Units on Tape and Reel
Pin Description
Label
Pin #
Function
Typical Connection
SDA
1
Serial Bi-Directional Data Line. Open Drain Output
From Controller
SCL
2
Serial Bus Clock Input
From Controller
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 3V to 5.5V
A0A1
7,6
User-Set Address Inputs
Ground (Low, "0") or +V
S
(High, "1")
DS100136-1
SOP8 or MSOP
DS100136-2
LM77 See NS Package Number M08A or MM08A
LM77
www.national.com
2
Pin Description
(Continued)
DS100136-3
FIGURE 1. Typical Application
LM77
www.national.com
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
5 mA
Package Input Current (Note 2)
20 mA
T_CRIT_A and INT Output Sink
Current
10 mA
T_CRIT_A and INT Output
Voltage
6.5V
Storage Temperature
-65C to +125C
Soldering Information, Lead
Temperature
SOP and MSOP Package (Note 3)
Vapor Phase (60 seconds)
215C
Infrared (15 seconds)
220C
ESD Susceptibility (Note 4)
Human Body Model
2500V
Machine Model
250V
Operating Ratings
(Notes 1, 5)
Specified Temperature Range
T
MIN
to T
MAX
(Note 6)
-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
=+5 Vdc
10% for LM77CIM-5, LM77CIMM-5 and +V
S
=+3.3 Vdc
10% for LM77CIM-3, LM77CIMM-3 (Note 7). 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
(Note 8)
Limits
(Note 9)
Units
(Limit)
Accuracy
T
A
= -10C to +65C
1.5
C (max)
T
A
= -25C to +100C
2.0
T
A
= -55C to +125C
3.0
Resolution
(Note 10)
10
0.5
Bits
C
Temperature Conversion Time
(Note 11)
70
125
ms
Quiescent Current
I
2
C Inactive
0.25
mA
I
2
C Active
0.25
0.5
mA (max)
Shutdown Mode
5
10
A
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
C
Default Temperature
(Note 14)
80
C
Logic Electrical Characteristics
DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for +V
S
=+5 Vdc
10% for LM77CIM-5,
LM77CIMM-5 and +V
S
=+3.3 Vdc
10% for LM77CIM-3, LM77CIMM-3. 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)
V
IN(0)
SDA and SCL Logical "0" Input
Voltage
-0.3
V (min)
+V
S
x 0.3
V (max)
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
LM77
www.national.com
4
Logic Electrical Characteristics
(Continued)
DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for +V
S
=+5 Vdc
10% for LM77CIM-5,
LM77CIMM-5 and +V
S
=+3.3 Vdc
10% for LM77CIM-3, LM77CIMM-3. 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)
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
LM77
www.national.com
5
PDF 
ZIP