General Description

reports the temperature of both a remote P-N junction

and its own die. The remote junction can be a diode-con-

nected transistor—typically a low-cost, easily mounted

2N3904 NPN type or 2N3906 PNP type—that replaces

conventional thermistors or thermocouples. Remote

accuracy is ±1°C for multiple transistor manufacturers,

with no calibration needed. The remote junction can also

be a common-collector PNP, such as a substrate PNP of

a microprocessor (µP).

The 2-wire serial interface accepts standard System

Send Byte, and Receive Byte commands to program the

alarm thresholds and to read temperature data.

Measurements can be done automatically and

autonomously, with the conversion rate programmed by

the user, or programmed to operate in a single-shot

mode. The adjustable conversion rate allows the user to

optimize supply current and temperature update rate to

match system needs. When the conversion rate is faster

than 1Hz, the conversion results are available as a 7-bit-

plus-sign byte with a 1°C LSB. When the conversion rate

is 1Hz or slower, the MAX6654 enters the extended

mode. In this mode, 3 additional bits of temperature data

are available in the extended resolution register, provid-

ing 10-bit-plus-sign resolution with a 0.125°C LSB.

Single-shot conversions also have 0.125°C per LSB reso-

lution when the conversion rate is 1Hz or slower.

A parasitic resistance cancellation (PRC) mode can also

be invoked for conversion rates of 1Hz or slower by set-

ting bit 4 of the configuration register to 1. In PRC mode,

the effect of series resistance on the leads of the external

diode is canceled. The 11-bit conversion in PRC mode is

performed in <500ms and is disabled for conversion

rates faster than 1Hz. The one-shot conversion is also 11

bits in <500ms.

The MAX6654 default low-temperature measurement

limit is 0°C. This can be extended to -64°C by setting bit

5 of the configuration register to 1.

The MAX6654 is available in a small, 16-pin QSOP sur-

face-mount package.

________________________Applications

Features

o High Accuracy ±1°C (max) from +70°C to +100°C

(Remote)

o 11-Bit, 0.125°C Resolution

o Dual Channel: Measures Remote and Local

Temperature

o No Calibration Required

o Programmable Under/Overtemperature Alarms

o +3V to +5.5V Supply Range

1°C Accurate Remote/Local Temperature

Sensor with SMBus Serial Interface

________________________________________________________________ Maxim Integrated Products

1

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

N.C.

N.C.

STBY

SMBCLK

N.C.

SMBDATA

ALERT

ADD0

N.C.

TOP VIEW

MAX6654

QSOP

DXP

ADD1

DXN

N.C.

GND

GND

Pin Configuration

DXP

CPU

DXN

STBY

10k EACH

CLOCK

DATA

INTERRUPT TO

µC

+3V TO +5V SUPPLY

200

Ω

0.1

µF

SMBCLK

SMBDATA

ALERT

GND

ADD0 ADD1

2200pF

MAX6654

Typical Operating Circuit

19-1836; Rev 2; 1/02

Ordering Information

Desktop Computers

Notebook Computers

Servers

Thin Clients

Workstations

Test and Measurement

Multichip Modules

SMBus is a trademark of Intel Corp.

PART

TEMP. RANGE

PIN-PACKAGE

MAX6654MEE

-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.