REV. 0

–12–

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

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.

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

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.

ALERT

GND

THERM

D+

D–

ADM1032

SCLK

SDATA

3V TO 3.6V

TYP 10k

0.1 F

SHIELD

2N3906

OR

CPU THERMAL

DIODE

SMBUS

CONTROLLER

TYP 10k

FAN CONTROL

CIRCUIT

5V OR 12V

FAN ENABLE

Figure 7. Typical Application Circuit

8-Lead SO

(R-8)

0.0098 (0.25)

0.0075 (0.19)

0.0500 (1.27)

0.0160 (0.41)

8

0

0.0196 (0.50)

0.0099 (0.25)

45

85

4

1

0.1968 (5.00)

0.1890 (4.80)

0.2440 (6.20)

0.2284 (5.80)

PIN 1

0.1574 (4.00)

0.1497 (3.80)

0.0500 (1.27)

BSC

0.0688 (1.75)

0.0532 (1.35)

SEATING

PLANE

0.0098 (0.25)

0.0040 (0.10)

0.0192 (0.49)

0.0138 (0.35)

8-Lead Micro_SO

(RM-8)

0.009 (0.23)

0.003 (0.08)

0.028 (0.71)

0.016 (0.41)

6

0

0.120 (3.05)

0.112 (2.84)

85

4

1

0.122 (3.10)

0.114 (2.90)

0.199 (5.05)

0.187 (4.75)

PIN 1

0.0256 (0.65) BSC

0.122 (3.10)

0.114 (2.90)

SEATING

PLANE

0.006 (0.15)

0.002 (0.05)

0.015 (0.38)

0.009 (0.22)

0.043 (1.09)

0.037 (0.94)

0.120 (3.05)

0.112 (2.84)

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).