ADM1032ARM ON Semiconductor, ADM1032ARM Datasheet - Page 15

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ADM1032ARM

Manufacturer Part Number
ADM1032ARM
Description
IC TEMP MONITOR 85DEG C 8MSOP
Manufacturer
ON Semiconductor
Datasheet

Specifications of ADM1032ARM

Rohs Status
RoHS non-compliant
Function
Temp Monitoring System (Sensor)
Topology
ADC, Comparator, Multiplexer, Register Bank
Sensor Type
External & Internal
Sensing Temperature
0°C ~ 100°C, External Sensor
Output Type
SMBus™
Output Alarm
Yes
Output Fan
Yes
Voltage - Supply
3 V ~ 5.5 V
Operating Temperature
0°C ~ 100°C
Mounting Type
Surface Mount
Package / Case
8-MSOP, Micro8™, 8-uMAX, 8-uSOP,

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Layout Considerations
the ADM1032 is measuring very small voltages from the
remote sensor, so care must be taken to minimize noise
induced at the sensor inputs. The following precautions
should be taken.
GND
GND
D+
D–
Digital boards can be electrically noisy environments, and
Figure 18. Typical Arrangement of Signal Tracks
1. Place the ADM1032 as close as possible to the
2. Route the D+ and D− tracks close together, in
3. Use wide tracks to minimize inductance and
4. Try to minimize the number of copper/solder
5. Place a 0.1 mF bypass capacitor close to the V
6. If the distance to the remote sensor is more than
7. For really long distances (up to 100 feet), use
remote sensing diode. Provided that the worst
noise sources, that is, clock generators,
data/address buses, and CRTs, are avoided, this
distance can be four to eight inches.
parallel, with grounded guard tracks on each side.
Provide a ground plane under the tracks if
possible.
reduce noise pickup. 10 mil track minimum width
and spacing is recommended.
joints, which can cause thermocouple effects.
Where copper/solder joints are used, make sure
that they are in both the D+ and D− path and at the
same temperature.
Thermocouple effects should not be a major
problem since 1°C corresponds to about 200 mV
and thermocouple voltages are about 3 mV/°C of
temperature difference. Unless there are two
thermocouples with a big temperature differential
between them, thermocouple voltages should be
much less than 200 mV.
pin. In very noisy environments, place a 1000 pF
input filter capacitor across D+ and D− close to the
ADM1032.
eight inches, the use of twisted pair cable is
recommended. This works up to about six feet to
12 feet.
shielded twisted pair, such as Belden #8451
http://onsemi.com
DD
10MIL
10MIL
10MIL
10MIL
10MIL
10MIL
10MIL
15
current sources, excessive cable and/or filter capacitance
can affect the measurement. When using long cables, the
filter capacitor can be reduced or removed.
resistance introduces about 1°C error.
Power Sequencing Considerations
Power Supply Slew Rate
the slew rate of V
than this may cause power−on−reset issues and yield
unpredictable results.
THERM Pin Pullup
requires a pullup to V
be pulled up to the same power supply as the ADM1032,
unlike the SMBus signals (SDA, SCL and ALERT) that can
be pulled to a different power rail. The only time the
THERM pin can be pulled to a different supply rail (other
than V
with, or after the ADM1032 main V
internal circuitry of the ADM1032. If the THERM pullup
supply rail were to rise before V
not operate correctly.
Application Circuit
ADM1032, using a discrete sensor transistor connected via
a shielded, twisted pair cable. The pullups on SCLK,
SDATA, and ALERT are required only if they are not
already provided elsewhere in the system.
interfaced directly to the SMBus of an I/O controller, such
as the Intel 820 chipset.
CPU THERMAL
Because the measurement technique uses switched
Cable resistance can also introduce errors. 1 W series
When powering up the ADM1032 you must ensure that
As mentioned above, the THERM signal is open drain and
Figure 20 shows a typical application circuit for the
The SCLK and SDATA pins of the ADM1032 can be
2N3906
DIODE
OR
DD
microphone cable. Connect the twisted pair to D+
and D− and the shield to GND close to the
ADM1032. Leave the remote end of the shield
unconnected to avoid ground loops.
) is if the other supply is powered up simultaneous
Figure 19. Typical Application Circuit
SHIELD
DD
D+
D–
ADM1032
is less than 18 mV/ms. A slew rate larger
DD
GND
SDATA
THERM
ALERT
. The THERM signal must always
SCLK
V
DD
0.1m F
ENABLE
DD
FAN
V
DD
TYP 10kW
DD
, the POR circuitry may
. This is to protect the
TYP 10kW
CONTROL
CIRCUIT
FAN
CONTROLLER
SMBUS
3V TO 3.6V
5V OR 12V

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