ADT7481
Dual Channel Temperature
Sensor and Overtemperature
Alarm
The ADT7481 is a 3-channel digital thermometer and under/ over
temperature alarm, intended for use in PCs and thermal management
systems. It can measure its own ambient temperature or the
temperature of two remote thermal diodes. These thermal diodes can
be located in a CPU or GPU, or they can be discrete diode connected
transistors. The ambient temperature, or the temperature of the remote
thermal diode, can be accurately measured to
±1°C.
The temperature
measurement range defaults to 0°C to +127°C, compatible with
ADM1032, but can be switched to a wider measurement range from
−64°C to +191°C.
The ADT7481 communicates over a 2-wire serial interface
compatible with System Management Bus (SMBus) standards. The
SMBus address of the ADT7481 is 0x4C. An ADT7481−1 with an
SMBus address of 0x4B is also available.
An ALERT output signals when the on-chip or remote temperature
is outside the programmed limits. The THERM output is a comparator
output that allows, for example, on/off control of a cooling fan. The
ALERT output can be reconfigured as a second THERM output if
required.
Features
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MSOP−10
CASE 846AC
PIN ASSIGNMENT
V
DD
D1+
D1−
THERM
GND
1
2
3
4
5
10
SCLK
9
SDATA
ALERT/THERM2
D2+
D2−
ADT7481
8
7
6
MARKING DIAGRAM
10
T0x
AYWG
G
1
T0x
A
Y
W
G
= Refer to Ordering Info Table
= Assembly Location
= Year
= Work Week
= Pb-Free Package
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
1 Local and 2 Remote Temperature Sensors
0.25°C Resolution/1°C Accuracy on Remote Channels
1°C Resolution/1°C Accuracy on Local Channel
Extended, Switchable Temperature Measurement Range
0°C to 127°C (Default) or −64°C to +191°C
2-wire SMBus Serial Interface with SMBus ALERT Support
Programmable Over/Undertemperature Limits
Offset Registers for System Calibration
Up to 2 Overtemperature Fail-Safe THERM Outputs
Small 10-lead MSOP Package
240
mA
Operating Current, 5
mA
Standby Current
These Devices are Pb-Free, Halogen Free and are RoHS Compliant
(Note: Microdot may be in either location)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 19 of this data sheet.
Applications
Desktop and Notebook Computers
Industrial Controllers
Smart Batteries
Automotive
Embedded Systems
Burn-In Applications
Instrumentation
©
Semiconductor Components Industries, LLC, 2014
1
September, 2014 − Rev. 8
Publication Order Number:
ADT7481/D
ADT7481
ADDRESS POINTER
REGISTER
ON-CHIP
TEMPERATURE
SENSOR
CONVERSION RATE
REGISTER
LOCAL TEMPERATURE
VALUE REGISTER
DIGITAL MUX
LIMIT COMPARATOR
ONE-SHOT
REGISTER
LOCAL TEMPERATURE
THERM LIMIT REGISTER
LOCAL TEMPERATURE
LOW LIMIT REGISTER
LOCAL TEMPERATURE
HIGH LIMIT REGISTER
REMOTE 1 & 2 TEMP.
THERM LIMIT REG.
REMOTE 1 & 2 TEMP.
LOW LIMIT REGISTERS
REMOTE 1 & 2 TEMP.
HIGH LIMIT REGISTERS
CONFIGURATION
REGISTER
EXTERNAL DIODE OPEN-CIRCUIT
STATUS REGISTERS
INTERRUPT
MASKING
D1+
D1−
D2+
D2−
2
3
7
6
ANALOG
MUX
11-BIT A-TO-D
CONVERTER
BUSY
RUN/STANDBY
REMOTE 1 AND 2 TEMP
VALUE REGISTER
REMOTE 1 AND 2 TEMP
OFFSET REGISTER
ADT7481
1
V
DD
5
GND
SMBUS INTERFACE
9
SDATA
10
SCLK
4
THERM
8
ALERT/THERM2
Figure 1. Functional Block Diagram
Table 1. ABSOLUTE MAXIMUM RATINGS
Parameter
Positive Supply Voltage (V
DD
) to GND
D+
D− to GND
SCLK, SDATA, ALERT, THERM
Input Current, SDATA, THERM
Input Current, D−
ESD Rating, All Pins (Human Body Model)
Maximum Junction Temperature (T
J MAX
)
Storage Temperature Range
IR Reflow Peak Temperature
IR Reflow Peak Temperature for Pb-Free
Lead Temperature, Soldering (10 sec)
Rating
−0.3 to +3.6
−0.3 to V
DD
+ 0.3
−0.3 to +0.6
Unit
V
V
V
V
mA
mA
V
°C
°C
°C
°C
°C
−0.3 to +3.6
−1 to +50
±1
1,500
150
−65 to +150
220
260
300
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
NOTE: This device is ESD sensitive. Use standard ESD precautions when handling.
Table 2. THERMAL CHARACTERISTICS
Package Type
10-lead MSOP
q
JA
142
q
JC
43.74
Unit
°C/W
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ADT7481
Table 3. PIN ASSIGNMENT
Pin No.
1
2
3
4
5
6
7
8
9
10
Mnemonic
V
DD
D1+
D1−
THERM
GND
D2−
D2+
ALERT/THERM2
SDATA
SCLK
Positive Supply, 3.0 V to 3.6 V.
Positive Connection to the Remote 1 Temperature Sensor.
Negative Connection to the Remote 1 Temperature Sensor.
Open-Drain Output. Requires pullup resistor. Signals overtemperature events, could be used to turn a
fan on/off, or throttle a CPU clock.
Supply Ground Connection.
Negative Connection to the Remote 2 Temperature Sensor.
Positive Connection to the Remote 2 Temperature Sensor.
Open-Drain Logic Output. Used as interrupt or SMBALERT. This may also be configured as a second
THERM output. Requires pullup resistor.
Logic Input/Output, SMBus Serial Data. Open-Drain Output. Requires pullup resistor.
Logic Input, SMBus Serial Clock. Requires pullup resistor.
Description
Table 4. TIMING SPECIFICATIONS
(Note 1)
Parameter
f
SCLK
t
LOW
t
HIGH
t
R
t
F
t
SU; STA
t
HD; STA
(Note 2)
t
SU; DAT
(Note 3)
t
HD; DAT
t
SU; STO
(Note 4)
t
BUF
1.
2.
3.
4.
Limit at T
MIN
and T
MAX
400
1.3
0.6
300
300
600
600
100
300
600
1.3
Unit
kHz max
ms
min
ms
min
ns max
ns max
ns min
ns min
ns min
ns min
ns min
ms
min
Clock low period, between 10% points.
Clock high period, between 90% points.
Clock/data rise time.
Clock/data fall time.
Start condition setup time.
Start condition hold time.
Data setup time.
Data hold time.
Stop condition setup time.
Bus free time between stop and start conditions.
Description
Guaranteed by design, not production tested.
Time from 10% of SDATA to 90% of SCLK.
Time for 10% or 90% of SDATA to 10% of SCLK.
Time for 90% of SCLK to 10% of SDATA.
t
LOW
t
R
SCLK
t
F
t
HD; STA
t
HD; STA
t
HD; DAT
t
HIGH
t
SU; DAT
t
SU; STA
t
SU; STO
SDATA
t
BUF
STOP START
START
STOP
Figure 2. Serial Bus Timing
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ADT7481
Table 5. ELECTRICAL CHARACTERISTICS
(T
A
= −40°C to +120°C, V
DD
= 3.0 V to 3.6 V, unless otherwise noted)
Parameter
Power Supply
Supply Voltage, V
DD
Average Operating Supply Current, I
DD
Undervoltage Lockout Threshold
Power-On-Reset Threshold
Temperature-to-Digital Converter
Local Sensor Accuracy (Note 2)
0°C
≤
T
A
≤
+70°C
0°C
≤
T
A
≤
+85°C
−40
≤
T
A
≤
+100°C
0°C
≤
T
A
≤
+70°C, −55°C
≤
T
D
(Note 3)
≤
+150°C
0°C
≤
T
A
≤
+85°C, −55°C
≤
T
D
(Note 3)
≤
+150°C
−40°C
≤
T
A
≤
+100°C, −55°C
≤
T
D
(Note 3)
≤
+150°C
High Level (Note 4)
Low Level (Note 4)
Conversion Time
From Stop Bit to Conversion Complete (Both
Channels) One-shot Mode with Averaging
Switched On
One-shot Mode with Averaging Off
(Conversion Rate = 16, 32, or 64 Conversions
per Second)
Open-Drain Digital Outputs (THERM, ALERT/THERM2)
Output Low Voltage, V
OL
High Level Output Leakage Current, I
OH
SMBus Interface
(Notes 4 and 5)
Logic Input High Voltage, V
IH
SCLK, SDATA
Logic Input Low Voltage, V
IL
SCLK, SDATA
Hysteresis
SDA Output Low Voltage, V
OL
Logic Input Current, I
IH
, I
IL
SMBus Input Capacitance,
SCLK, SDATA
SMBus Clock Frequency
SMBus Timeout (Note 6)
SCLK Falling Edge to SDATA Valid Time
1.
2.
3.
4.
5.
6.
User Programmable
Master Clocking in Data
I
OUT
= −6.0 mA
2.1
−
−
−
−1.0
−
−
−
−
−
−
500
−
−
5.0
−
25
−
−
0.8
−
0.4
+1.0
−
400
32
1.0
V
V
mV
V
mA
pF
kHz
ms
ms
I
OUT
= −6.0 mA
V
OUT
= V
DD
−
−
−
0.1
0.4
1.0
V
mA
−
−
−
−
−
−
−
−
−
−
−
−
−
−
1.0
−
−
−
0.25
233
14
73
±1
±1.5
±2.5
−
±1
±1.5
±2.5
−
−
−
94
°C
0.0625 Conversions/Sec Rate (Note 1)
Standby Mode
V
DD
Input, Disables ADC, Rising Edge
3.0
−
−
−
1.0
3.30
3.0
5.0
2.55
−
3.6
4.0
30
−
2.5
V
mA
mA
V
V
Conditions
Min
Typ
Max
Unit
Resolution
Remote Diode Sensor Accuracy (Note 2)
°C
°C
Resolution
Remote Sensor Source Current
°C
mA
mA
ms
−
11
14
ms
See Table 11 for information on other conversion rates.
Averaging enabled.
Guaranteed by characterization, not production tested.
Guaranteed by design, not production tested.
See Timing Specifications section for more information.
Disabled by default. See the Serial Bus Interface section for details to enable it.
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ADT7481
TYPICAL PERFORMANCE CHARACTERISTICS
3.5
TEMPERATURE ERROR (°C)
TEMPERATURE ERROR (°C)
3.0
2.5
2.0
1.5
1.0
0.5
0
−0.5
−1.0
−50
0
50
TEMPERATURE (°C)
100
150
DEV 1
DEV 2
DEV 3
DEV 4
DEV 5
DEV 6
DEV 7
DEV 8
DEV 9
DEV 10
DEV 11
DEV 12
DEV 13
DEV 14
DEV 15
DEV 16
MEAN
HIGH 4S
LOW 4S
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
−0.5
−1.0
−50
0
50
TEMPERATURE (°C)
100
150
DEV 1
DEV 2
DEV 3
DEV 4
DEV 5
DEV 6
DEV 7
DEV 8
DEV 9
DEV 10
DEV 11
DEV 12
DEV 13
DEV 14
DEV 15
DEV 16
HIGH 4S
LOW 4S
Figure 3. Local Temperature Error vs. Temperature
Figure 4. Remote 1 Temperature Error
vs. Temperature
10
TEMPERATURE ERROR (°C)
3.5
TEMPERATURE ERROR (°C)
3.0
2.5
2.0
1.5
1.0
0.5
0
−0.5
−1.0
−50
0
DEV 1
DEV 2
DEV 3
DEV 4
DEV 5
DEV 6
DEV 7
DEV 8
DEV 9
DEV 10
DEV 11
DEV 12
DEV 13
DEV 14
DEV 15
DEV 16
MEAN
HIGH 4S
LOW 4S
5
0
−5
−10
−15
−20
−25
D+ To GND
D+ To V
CC
50
TEMPERATURE (°C)
100
150
1
10
LEAKAGE RESISTANCE (MW)
100
Figure 5. Remote 2 Temperature Error
vs. Temperature
0
TEMPERATURE ERROR (°C)
−2
−4
−6
−8
−10
DEV 3
−12
−14
DEV 4
−16
−18
0
5
10
15
20
25
CAPACITANCE (nF)
DEV 2
Figure 6. Temperature Error vs. D+/D− Leakage
Resistance
1000
900
800
700
I
DD
(mA)
600
500
400
300
200
100
0
0.01
0.1
1
10
100
DEV 3BC
DEV 4BC
DEV 2BC
CONVERTION RATE (Hz)
Figure 7. Temperature Error vs. D+/D− Capacitance
Figure 8. Operating Supply Current
vs. Conversion Rate
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