ADM1032
Thermocouple effects should not be a major problem as 1°C
corresponds to about 200 V, and thermocouple voltages are
about 3 V/°C of temperature difference. Unless there are two
thermocouples with a big temperature differential between them,
thermocouple voltages should be much less than 200 V.
5. Place a 0.1
µF
bypass capacitor close to the V
DD
pin. In very
noisy environments place a 2200 pF input filter capacitors
across D+, D– close to the ADM1032.
6. If the distance to the remote sensor is more than 8 inches, the
use of twisted pair cable is recommended. This will work up
to about 6 to 12 feet.
7. For really long distances (up to 100 feet) use shielded twisted
pair such as Belden #8451 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.
0.1 F
V
DD
3V TO 3.6V
TYP 10k
Because the measurement technique uses switched current
sources, excessive cable and/or filter capacitance can affect the
measurement. When using long cables, the filter capacitor may
be reduced or removed.
Cable resistance can also introduce errors. 1
Ω
series resistance
introduces about 1°C error.
APPLICATION CIRCUIT
C01906–.8–10/01(0)
PRINTED IN U.S.A.
Figure 7 shows a typical application circuit for the ADM1032,
using a discrete sensor transistor connected via a shielded,
twisted pair cable. The pull-ups on SCLK, SDATA, and
ALERT
are required only if they are not already provided elsewhere
in the system.
The SCLK, and SDATA pins of the ADM1032 can be inter-
faced directly to the SMBus of an I/O controller such as the
Intel 820 chipset.
ADM1032
D+
SCLK
D–
SHIELD
2N3906
OR
CPU THERMAL
DIODE
SDATA
ALERT
THERM
V
DD
SMBUS
CONTROLLER
5V OR 12V
GND
TYP 10k
FAN CONTROL
CIRCUIT
FAN ENABLE
Figure 7. Typical Application Circuit
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead SO
(R-8)
0.1968 (5.00)
0.1890 (4.80)
8
5
4
8-Lead Micro_SO
(RM-8)
0.122 (3.10)
0.114 (2.90)
0.1574 (4.00)
0.1497 (3.80)
PIN 1
1
0.2440 (6.20)
0.2284 (5.80)
8
5
0.122 (3.10)
0.114 (2.90)
1
4
0.199 (5.05)
0.187 (4.75)
0.0500 (1.27)
BSC
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
0.0688 (1.75)
0.0532 (1.35)
0.0192 (0.49)
0.0138 (0.35)
8
0.0098 (0.25) 0
0.0075 (0.19)
0.0196 (0.50)
0.0099 (0.25)
45
PIN 1
0.0256 (0.65) BSC
0.120 (3.05)
0.112 (2.84)
0.006 (0.15)
0.002 (0.05)
0.015 (0.38)
SEATING 0.009 (0.22)
PLANE
0.043 (1.09)
0.037 (0.94)
0.009 (0.23)
0.003 (0.08)
0.120 (3.05)
0.112 (2.84)
6
0
0.0500 (1.27)
0.0160 (0.41)
0.028 (0.71)
0.016 (0.41)
–12–
REV. 0
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