LM32
Dual Thermal Diode Temperature Sensor with
SensorPath
TM
Bus
General Description
The LM32 is a digital temperature sensor that measures 3
temperature zones and has a single-wire interface compat-
ible with National Semiconductor's SensorPath bus. Sensor-
Path data is pulse width encoded, thereby allowing the LM32
to be easily connected to many general purpose micro-
controllers. Several National Semiconductor Super I/O prod-
ucts include a fully integrated SensorPath master, that when
connected to an LM32 can realize a hardware monitor func-
tion that includes limit checking for measured values, au-
tonomous fan speed control and many other functions.
The LM32 measures the temperature of its own die as well
as two external devices such as a processor thermal diode
or a diode connected transistor. The LM32 can resolve tem-
peratures up to 255C and down to -256C. The operating
temperature range of the LM32 is 0C to +125C. The ad-
dress programming pin allows two LM32s to be placed on
one SensorPath bus.
Features
n
SensorPath Interface
-- 2 hardware programmable addresses
n
2 remote diode temperature sensor zones
n
Internal local temperature zone
n
0.5 C resolution
n
Measures temperatures up to 140 C
n
14-lead TSSOP package
Key Specifications
n
Temperature Sensor Accuracy
3 C (max)
n
Temperature Range:
-- LM32 junction
0 C to +85 C
-- Remote Temp Accuracy
0 C to +100 C
n
Power Supply Voltage
+3.0 V to +3.6 V
n
Average Power Supply Current
0.5 mA (typ)
n
Conversion Time (all Channels)
22.5ms to 1456ms
Applications
n
Microprocessor based equipment
(Motherboards, Video Cards, Base-stations, Routers,
ATMs, Point of Sale, ...)
n
Power Supplies
Typical Application
20071101
SensorPath
TM
is a trademark of National Semiconductor Corporation
May 2004
LM32
Dual
Thermal
Diode
T
emperature
Sensor
with
SensorPath
TM
Bus
2004 National Semiconductor Corporation
DS200711
www.national.com
Connection Diagram
TSSOP-14
20071102
Top View
National Package Number MTC14C
Order
Number
Package
Marking
NS
Package
Number
Transport
Media
LM32CIMT
LM32
CIMT
MTC14C
94 units per
rail
LM32CIMTX
LM32
CIMT
MTC14C
2500 units in
tape and reel
Pin Description
Pin Number
Pin Name
Description
Typical Connection
1, 6, 7,12, 13,
14
NC
No Connect
May be tied to V+, GND or left floating
2
GND
Ground
System ground
3
V+/+3.3V_SBY
Positive power supply pin
Connected system 3.3 V standby power and
to a 0.1 F bypass capacitor in parallel with
100 pF. A bulk capacitance of approximately
10 F needs to be in the near vicinity of the
LM32.
4
SWD
SensorPath Bus line; Open-drain
output
Super I/O, Pull-up resistor, 1.6k
5
ADD
Digital input - device number select
input for the serial bus device
number
Pull-up to 3.3 V or pull-down to GND resistor,
10k; must never be left floating
8, 10
D1-, D2-
Thermal diode analog voltage
output and negative monitoring
input
Remote Thermal Diode cathode
(THERM_DC) - Diode 1 should always be
connected to the processor thermal diode.
Diode 2 may be connected to an MMBT3904
or GPU thermal diode. A 100 pF capacitor
should be connected between respective D-
and D+ for noise filtering.
9, 11
D1+, D2+
Thermal diode analog current
output and positive monitoring input
Remote Thermal Diode anode (THERM_DA) -
Diode 1 should always be connected to the
processor thermal diode. Diode 2 may be
connected to an MMBT3904 or GPU thermal
diode. A 100 pF capacitor should be
connected between respective D- and D+ for
noise filtering.
LM32
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2
Block Diagram
20071103
LM32
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3
Absolute Maximum Ratings
(Notes 2, 1)
Supply Voltage (V
+
)
-0.5 V to 6.0 V
Voltage at Any Digital Input or
Output Pin
-0.5 V to 6.0 V
Voltage on D1+ and D2+
-0.5 V to (V+ + 0.05 V)
Current on D1- and D2-
1 mA
Input Current per Pin(Note 3)
5 mA
Package Input Current (Note 3)
30 mA
Package Power Dissipation
(Note 4)
Output Sink Current
10 mA
ESD Susceptibility (Note 5)
Human Body Model
2500 V
Machine Model
250 V
Storage Temperature
-65C to +150C
Soldering process must comply with National's reflow
temperature profile specifications. Refer to
www.national.com/packaging/. (Note 6)
Operating Ratings
(Notes 1, 2)
Temperature Range for Electrical Characteristics
LM32CIMT (T
MIN
T
A
T
MAX
)
0C
T
A
+85C
Operating Temperature Range
0C
T
A
+125C
Remote Diode Temperature (T
D
)
Range
-5C
T
D
+140 C
Supply Voltage Range (V+)
+3.0 V to +3.6 V
DC Electrical Characteristics
The following specifications apply for V+ = +3.0 V
DC
to +3.6 V
DC
, and all analog source impedance R
S
= 50
unless other-
wise specified in the conditions. Boldface limits apply for LM32CIMT T
A
= T
J
= T
MIN
=0C to T
MAX
=85C; all other limits
T
A
= +25C. T
A
is the ambient temperature of the LM32; T
J
is the junction temperature of the LM32; T
D
is the junction tem-
perature of the remote thermal diode.
POWER SUPPLY CHARACTERISTICS
Symbol
Parameter
Conditions
Typical
(Note 7)
Limits
(Note 8)
Units
(Limit)
V+
Power Supply Voltage
3.3
3.0
3.6
V (min)
V (max)
I+
Shutdown
Shutdown Power Supply Current
SensorPath Bus Inactive
(Note 9)
260
420
A (max)
I+
Average
Average Power Supply Current
SensorPath Bus Inactive; all
sensors enabled;
t
CONV
=182 ms; (Note 9)
900
A (max)
I+
Peak
Peak Power Supply Current
SensorPath Bus Inactive
(Note 9)
3.3
mA (max)
Power-On Reset Threshold Voltage
1.6
V (min)
2.8
V (max)
TEMPERATURE-TO-DIGITAL CONVERTER CHARACTERISTICS
Parameter
Conditions
Typical
(Note 7)
Limits
(Note 8)
Units
(Limits)
Temperature Accuracy Using the Remote Thermal
Diode, see (Note 11) for Thermal Diode Processor
Type.
T
J
= 0C to
+85C
T
D
= +25C
1
2.5
C (max)
T
J
= 0C to
+85C
T
D
= 0C to
+100C
3
C (max)
T
J
= 0C to
+85C
T
D
= +100C to
+125C
4
C (max)
Temperature Accuracy Using the Local Diode
T
J
= 0C to +85C (Note 10)
1
3
C (max)
Remote Diode and Local Temperature Resolution
10
Bits
0.5
C
D- Source Voltage
0.7
V
Diode Source Current
(V
D+
- V
D-
) = +0.65 V; High Current
188
280
A (max)
Low Current
11.75
A
Diode Source Current High Current to Low Current
Ratio
16
LM32
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4
SWD and ADD DIGITAL INPUT CHARACTERISTICS
Symbol
Parameter
Conditions
Typical
(Note 7)
Limits
(Note 8)
Units
(Limit)
V
IH
SWD Logical High Input Voltage
2.1
V (min)
V+ + 0.5
V (max)
V
IL
SWD Logical Low Input Voltage
0.8
V (max)
-0.5
V (min)
V
IH
ADD Logical High Input Voltage
90% x V+
V (min)
V
IL
ADD Logical Low Input Voltage
10% x V+
V (max)
V
HYST
Input Hysteresis
300
mV
I
L
SWD and ADD Input Current
GND
V
IN
V+
0.005
10
A (max)
SWD Input Current with V+ Open or
Grounded
GND
V
IN
3.6V,
and V+ Open or
GND
0.005
A
C
IN
Digital Input Capacitance
10
pF
SWD DIGITAL OUTPUT CHARACTERISTICS
Symbol
Parameter
Conditions
Typical
(Note 7)
Limits
(Note 8)
Units
(Limit)
V
OL
Open-drain Output Logic "Low"
Voltage
I
OL
= 4mA
0.4
V (max)
I
OL
= 50A
0.2
V (max)
I
OH
Open-drain Output Off Current
0.005
10
A (max)
C
OUT
Digital Output Capacitance
10
pF
AC Electrical Characteristics
The following specification apply for V+ = +3.0 V
DC
to +3.6 V
DC
, unless otherwise specified. Boldface limits apply for
T
A
= T
J
= T
MIN
=0C to T
MAX
=85C; all other limits T
A
= T
J
= 25C. The SensorPath Characteristics conform to the SensorPath
specification revision 0.98. Please refer to that speciation for further details.
Symbol
Parameter
Conditions
Typical
(Note 7)
Limits
(Note 8)
Units
(Limits)
HARDWARE MONITOR CHARACTERISTICS
t
CONV
Total Monitoring Cycle Time (Note 12)
All Temperature readings
(Default)
182
163.8
ms (min)
200.2
ms (max)
SensorPath Bus CHARACTERISTICS
t
f
SWD fall time (Note 15)
R
pull-up
=1.25 k
30%,
C
L
=400 pF
300
ns (max)
t
r
SWD rise time (Note 15)
R
pull-up
=1.25 k
30%,
C
L
=400 pF
1000
ns (max)
t
INACT
Minimum inactive time (bus at high level)
guaranteed by the slave before an attention
request
11
s (min)
t
Mtr0
Master drive for Data Bit 0 write and for Data
Bit 0-1read
11.8
s (min)
17.0
s (max)
t
Mtr1
Master drive for Data Bit 1 write
35.4
s (min)
48.9
s (max)
t
SFEdet
Time allowed for LM32 activity detection
9.6
s (max)
t
SLout1
LM32 drive for Data Bit 1 read by master
28.3
s (min)
38.3
s (max)
t
MtrS
Master drive for Start Bit
80
s (min)
109
s (max)
t
SLoutA
LM32 drive for Attention Request
165
s (min)
228
s (max)
t
RST
Master or LM32 drive for Reset
354
s (min)
LM32
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