The ADM1032 is a dual-channel digital thermometer and
under/over temperature alarm, intended for use in personal
computers and thermal management systems. The higher 1°C
accuracy offered allows systems designers to safely reduce
temperature guardbanding and increase system performance.
The device can measure the temperature of a microprocessor
using a diode-connected NPN or PNP transistor, which may be
provided on-chip or can be a low-cost discrete device such as
the 2N3906. A novel measurement technique cancels out the
absolute value of the transistor’s base emitter voltage, so that no
calibration is required. The second measurement channel measures the output of an on-chip temperature sensor, to monitor
the temperature of the device and its environment.
The ADM1032 communicates over a two-wire serial interface
compatible with System Management Bus (SMBus) standards.
Under and over temperature limits can be programmed into the
device over the serial bus, and an ALERT output signals when
the on-chip or remote temperature measurement is out of range.
This output can be used as an interrupt, or as an SMBus alert.
The THERM output is a comparator output that allows CPU
clock throttling or on/off control of a cooling fan.
*
ON-CHIP
TEMPERATURE
SENSOR
D+
ANALOG
D–
Pentium is a registered trademark of Intel Corporation.
*Patents 5,982,221, 6,097,239, 6,133,753, 6,169,442, 5,867,012.
MUX
BUSY
EXTERNAL DIODE OPEN-CIRCUIT
ADM1032
V
DD
A-TO-D
CONVERTER
GND
LOCAL TEMPERATURE
VALUE REGISTER
RUN/STANDBY
REMOTE TEMPERATURE
VALUE REGISTER
REMOTE OFFSET
REGISTER
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
Conversion Time35.7142.8msFrom Stop Bit to Conversion Complete
(Both Channels) One-Shot Mode with
Averaging Switched On
5.722.8msOne-Shot Mode with Averaging Off
(i.e., Conversion Rate = 32 or 64
Conversions per Second)
OPEN-DRAIN DIGITAL OUTPUTS
(THERM, ALERT)
Output Low Voltage, V
OL
High Level Output Leakage Current, I
SMBus INTERFACE
Logic Input High Voltage, V
2
IH
OH
0.4VI
0.11µAV
= –6.0 mA
OUT
= V
OUT
2.1VVDD = 3 V to 5.5 V
DD
2
2
SCLK, SDATA
Logic Input Low Voltage, V
IL
0.8VVDD = 3 V to 5.5 V
Hysteresis500mV
SCLK, SDATA
SMBus Output Low Sink Current6mASDATA Forced to 0.6 V
ALERT Output Low Sink Current1mAALERT Forced to 0.4 V
Logic Input Current, I
, I
IH
IL
–1+1µA
SMBus Input Capacitance, SCLK, SDATA5pF
SMBus Clock Frequency100kHz
SMBus Timeout2564msNote 3
SMBus Clock Low Time, t
SMBus Clock High Time, t
SMBus Start Condition Setup Time, t
SMBus Start Condition Hold Time, t
LOW
HIGH
SU:STA
HD:STA
4.7µst
4µst
4.7µs
4µsTime from 10% of SDATA to 90%
between 10% Points
LOW
between 90% Points
HIGH
of SCLK
SMBus Stop Condition Setup Time, t
SU:STO
4µsTime from 90% of SCLK to 10%
of SDATA
SMBus Data Valid to SCLK Rising Edge250nsTime for 10% or 90% of SDATA to
Time, t
SU:DAT
SMBus Data Hold Time, t
SMBus Bus Free Time, t
BUF
HD:DAT
300µs
4.7µsBetween Start/Stop Condition
10% of SCLK
SCLK Falling Edge to SDATA1µsMaster Clocking in Data
Valid Time, t
SCLK, SDATA Rise Time, t
SCLK, SDATA Fall Time, t
NOTES
1
See Table VI for information on other conversion rates.
2
Guaranteed by Design, not production tested.
3
The SMBus timeout is a programmable feature. By default it is not enabled. Details on how to enable it are available in the SMBus section of this data sheet.
Specifications subject to change without notice.
VD,DAT
R
F
1µs
300ns
–2–
REV. 0
ADM1032
ABSOLUTE MAXIMUM RATINGS*
Positive Supply Voltage (VDD) to GND . . . . . . –0.3 V, +5.5 V
*Stresses above those listed under Absolute Maximum Ratings may cause
permanent damage to the device. This is a stress rating only; functional operation
of the device at these or any other conditions above those indicated in the
operational section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
V
THERM
DD
D+
D–
1
2
ADM1032
TOP VIEW
3
(Not to Scale)
4
8
7
6
5
SCLK
SDATA
ALERT
GND
ORDERING GUIDE
TemperaturePackagePackageBrandingSMBus
ModelRangeDescriptionOptionInformationAddr
ADM1032AR0°C to 120°C8-Lead SO PackageSO-81032AR4C
ADM1032ARM0°C to 120°C8-Lead Micro_SO PackageRM-8T2A4C
SCLK
SDATA
t
t
BUF
PS
HD;STA
t
LOW
t
R
t
HD;DAT
t
HIGH
t
F
t
SU;DAT
t
HD;STA
t
SU;STA
S
t
SU;STO
P
Figure 1. Diagram for Serial Bus Timing
PIN FUNCTION DESCRIPTIONS
Pin
No.MnemonicDescription
1V
DD
Positive Supply, 3 V to 5.5 V.
2D+Positive Connection to Remote Temperature Sensor.
3D–Negative Connection to Remote Temperature Sensor.
4THERMOpen-drain output that can be used to turn a fan on/off or throttle a CPU clock in the event of an over-
temperature condition. Requires pull-up to V
DD
.
5GNDSupply Ground Connection
6ALERTOpen-Drain Logic Output Used as Interrupt or SMBus Alert.
7SDATALogic Input/Output, SMBus Serial Data. Open-Drain Output. Requires pull-up resistor.
8SCLKLogic Input, SMBus Serial Clock. Requires pull-up resistor.
REV. 0
–3–
ADM1032–Typical Performance Characteristics
20
16
12
8
4
0
–4
–8
TEMPERATURE ERROR – C
–12
–16
D+ TO GND
D+ TO V
DD
010100
LEAKAGE RESISTANCE – M
TPC 1. Temperature Error vs.
Leakage Resistance
12
10
8
6
4
TEMPERATURE ERROR – C
2
0
101M
= 250mV p-p
V
IN
= 100mV p-p
V
IN
FREQUENCY – Hz
1.0
0.5
0
TEMPERATURE ERROR – C
–0.5
0 20406080100120
TEMPERATURE – C
TPC 2. Temperature Error vs. Actual
Temperature Using 2N3906
18
16
14
12
10
8
6
4
TEMPERATURE ERROR – C
2
0
161116212631
CAPACITANCE – nF
36
13
11
9
7
5
3
TEMPERATURE ERROR – C
1
–1
100k100M1M
V
= 40mV p-p
IN
V
= 10mV p-p
IN
FREQUENCY – Hz
10M
TPC 3. Temperature Error vs.
Differential Mode Noise Frequency
2.0
1.5
1.0
= 5V
V
0.5
SUPPLY CURRENT – A
0
0.01
DD
VDD = 3V
0.1110100
CONVERSION RATE – Hz
TPC 4. Temperature Error vs. Power
Supply Noise Frequency
12
10
8
6
4
TEMPERATURE ERROR – C
2
0
100k1M10M100M
VIN = 100mV p-p
VIN = 50mV p-p
VIN = 25mV p-p
FREQUENCY – Hz
TPC 7. Temperature Error vs.
Common-Mode Noise Frequency
TPC 5. Temperature Error vs.
Capacitance between D+ and D–
80
70
60
50
40
30
20
SUPPLY CURRENT – A
10
0
1 5 10 25 50 75 100
SCLK FREQUENCY – kHz
V
5V
DD =
3.3V
V
DD =
250 500 750 1000
TPC 8. Standby Supply Current vs.
Clock Frequency
TPC 6. Operating Supply Current vs.
Conversion Rate
40
35
30
25
20
15
10
5
STANDBY SUPPLY CURRENT – A
0
0
1.52.50.5 1.03.05.03.5 4.0 4.52.0
SUPPLY VOLTAGE – V
TPC 9. Standby Supply Current vs.
Supply Voltage
–4–
REV. 0
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