Fan Controller and Remote Temperature Sensor

with SMBus Serial Interface

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7

_______________Detailed Description

The MAX1669 temperature sensor is designed to work

with an external microcontroller (µC) or other intelligent

devices in computer fan-control applications. The µC is

typically a power-management or keyboard controller,

generating SMBus serial commands by “bit-banging’’

general-purpose input/output (GPIO) pins or through a

dedicated SMBus interface block.

Essentially an 8-bit serial analog-to-digital converter

(ADC) with a sophisticated front end, the temperature

measurement channel contains a switched-current

source, a multiplexer, and an integrating ADC.

Temperature data from the ADC is loaded into a data

register, where it is automatically compared with data

previously stored in over/undertemperature alarm regis-

ters and the critical register (Figure 1).

MUX

REMOTE-TEMPERATURE

DATA REGISTER

HIGH-TEMPERATURE

THRESHOLD

LOW-TEMPERATURE

THRESHOLD

DIGITAL COMPARATOR

TEMPERATURE

TEMPERATURE SENSOR

COMMAND-BYTE

(INDEX) REGISTER

SMBDATA

SMBCLK

ADDRESS

DECODER

READ

WRITE

CONTROL

LOGIC

CONTROL

LOGIC

SMB

ADD2

ADD1

ADD0

STATUS BYTE REGISTER

CONFIGURATION

BYTE REGISTER

ALERT RESPONSE

ADDRESS REGISTER

ADC

DXP

DXN

GND

8

8

8

88

ALERT

MAX1669

SQ

R

CONTROL

LOGIC

OVERT

Q

R

S

GENERAL-PURPOSE

I/O CONTROLLER

-5°C

I/O1

I/O2

Figure 1. MAX1669 Temperature Sensor Functional Diagram