________________General Description

The MAX1668/MAX1805/MAX1989 are precise multi-

channel digital thermometers that report the tempera-

ture of all remote sensors and their own packages. The

remote sensors are diode-connected transistors—typi-

cally low-cost, easily mounted 2N3904 NPN types—that

replace conventional thermistors or thermocouples.

Remote accuracy is ±3°C for multiple transistor manu-

facturers, with no calibration needed. The remote chan-

nels can also measure the die temperature of other ICs,

such as microprocessors, that contain an on-chip,

diode-connected transistor.

The 2-wire serial interface accepts standard system

management bus (SMBus™) write byte, read byte, send

byte, and receive byte commands to program the alarm

thresholds and to read temperature data. The data for-

mat is 7 bits plus sign, with each bit corresponding to

1°C, in two’s-complement format.

The MAX1668/MAX1805/MAX1989 are available in

small, 16-pin QSOP surface-mount packages. The

MAX1989 is also available in a 16-pin TSSOP.

________________________Applications

____________________________Features

o Multichannel

4 Remote, 1 Local (MAX1668/MAX1989)

2 Remote, 1 Local (MAX1805)

o No Calibration Required

o SMBus 2-Wire Serial Interface

o Programmable Under/Overtemperature Alarms

o Supports SMBus Alert Response

o Accuracy

±2°C (+60°C to +100°C, Local)

±3°C (-40°C to +125°C, Local)

±3°C (+60°C to +100°C, Remote)

o 3µA (typ) Standby Supply Current

o 700µA (max) Supply Current

o Small, 16-Pin QSOP/TSSOP Packages

Multichannel Remote/Local

Temperature Sensors

________________________________________________________________ Maxim Integrated Products

1

SMBCLK

ADD0 ADD1

STBY

GND

ALERT

SMBDATA

DXP1

DXP4

DXN4

INTERRUPT

TO

µC

3V TO 5.5V

200

Ω

0.1

µF

CLOCK

10k

Ω EACH

DATA

DXN1

2200pF

2200pF

*

*

MAX1668

MAX1805

MAX1989

Pin Configuration

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

DXP1

GND

STBY

SMBCLK

SMBDATA

ALERT

ADD0

ADD1

TOP VIEW

MAX1668

MAX1805

MAX1989

QSOP/TSSOP

DXN1

DXP2

(N.C.) DXN3

DXN2

(N.C.) DXP3

(N.C.) DXP4

( ) ARE FOR MAX1805.

(N.C.) DXN4

Typical Operating Circuit

19-1766; Rev 2; 5/03

PART

MAX1668MEE

-55°C to +125°C

TEMP RANGE

PIN-PACKAGE

16 QSOP

_______________Ordering Information

SMBus is a trademark of Intel Corp.

†Patents Pending

MAX1805MEE

-55°C to +125°C

16 QSOP

Desktop and Notebook

Computers

LAN Servers

Industrial Controls

Central-Office Telecom

Equipment

Test and Measurement

Multichip Modules

MAX1989MEE

-55°C to +125°C

16 QSOP

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

MAX1989MUE

-55°C to +125°C

16 TSSOP