ADM1023

http://onsemi.com

15

noise pickup. 10 mil track minimum width and spacing

is recommended.

Figure 19. Arrangement of Signal Tracks

10MIL

GND

D+

GND

D–

10MIL

10MIL

10MIL

10MIL

10MIL

10MIL

10MIL

10MIL

10MIL

10MIL

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 as

1

°C corresponds to about 240 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 240

mV.

and 1000 pF input filter capacitors across D+, D− close

to the ADM1023.

inches, the use of twisted pair cable is recommended.

This is effective up to approximately 6 to 12 feet.

twisted−pair cable such as Belden #8451 microphone

cable. Connect the twisted pair to D+ and D−, and

connect the shield to GND close to the ADM1023.

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. A 1

W series

resistance introduces about 1

°C error.

Application Circuits

Figure 20 shows a typical application circuit for the

ADM1023, 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.

Figure 20. Typical Application Circuit

ALERT

GND

ADD0

D+

D–

ADM1023

ADD1

SET TO

REQUIRED

ADDRESS

3V

TO 5.5V

TO

CONTROL

CHIP

10kΩ 10kΩ

0.1μF

SHIELD

2N3904

1000pF

10kΩ

IN

I/O

OUT

The SCLK and SDATA pins of the ADM1023 can be

interfaced directly to the SMBus of an I/O chip. Figure 21

shows how the ADM1023 might be integrated into a system

using this type of I/O controller.

Figure 21. System Using ADM1023 and I/O Controller

2 USB PORTS

ICH I/O

CONTROLLER

HUB

CD ROM

HARD

DISK

SYSTEM

MEMORY

PROCESSOR

GMCH

DISPLAY

DISPLAY

CACHE

ADM1023

D+

D–

SYSTEM BUS

PCI BUS

PCI SLOTS

USB

USB

FWH

(FIRMWARE

HUB)

SUPER I/O

SMBUS

2 IDE PORTS

ORDERING INFORMATION

Device Number

Temperature Range

Package Type

Package Option

ADM1023ARQZ

0

°C to +120°C

16−Lead QSOP

RQ−16

98 Tube

ADM1023ARQZ−REEL

0

°C to +120°C

16−Lead QSOP

RQ−16

2500 Tape & Reel

ADM1023ARQZ−R7

0

°C to +120°C

16−Lead QSOP

RQ−16

1000 Tape & Reel

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.

*The “Z’’ suffix indicates Pb−Free part.