MAX6639(2005) Просмотр технического описания (PDF) - Maxim Integrated

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MAX6639
(Rev.:2005)

2-Channel Temperature Monitor with Dual, Automatic, PWM Fan-Speed Controller

Maxim Integrated 

2-Channel Temperature Monitor with Dual,

Automatic, PWM Fan-Speed Controller

Block Diagram

Detailed Description

VCC

MAX6639

DXP1

DXN

DXP2

TEMPERATURE

PROCESSING

BLOCK

PWM

GENERATOR

BLOCK

PWM1

PWM2

The MAX6639 monitors its own temperature and a

remote-diode-connected transistor or the temperatures

of two external-diode-connected transistors, which typi-

cally reside on the die of a CPU or other integrated cir-

cuit. The 2-wire serial interface accepts standard

SMBus write byte, read byte, send byte, and receive

byte commands to read the temperature data and pro-

gram the alarm thresholds. Temperature data can be

read at any time over the SMBus, and a programmable

alarm output can be used to generate interrupts, throt-

tle signals, or overtemperature shutdown signals.

ADD

SMBus

INTERFACE AND

SDA

REGISTERS

LOGIC

OT

THERM

FANFAIL

ALERT

The temperature data is also used by the internal dual-

PWM fan-speed controller to adjust the speed of up to

two cooling fans, thereby minimizing noise when the

system is running cool, but providing maximum cooling

when power dissipation increases. RPM feedback

allows the MAX6639 to control the fan’s actual speed.

SCL

TACH1

TACH2

GND

Write Byte Format

S

ADDRESS

WR

ACK

COMMAND

ACK

DATA

ACK

P

7 bits

Slave Address: equiva-

lent to chip-select line of

a 3-wire interface

Read Byte Format

8 bits

Command Byte: selects which

register you are writing to

8 bits

1

Data Byte: data goes into the register

set by the command byte (to set

thresholds, configuration masks, and

sampling rate)

S ADDRESS WR ACK COMMAND ACK

S ADDRESS RD ACK DATA

///

P

7 bits

Slave Address: equiva-

lent to chip-select line

8 bits

Command Byte: selects

which register you are

reading from

7 bits

Slave Address: repeated

due to change in data-

flow direction

8 bits

Data Byte: reads from

the register set by the

command byte

Send Byte Format

Receive Byte Format

S ADDRESS WR ACK COMMAND ACK P

S

7 bits

8 bits

Command Byte: sends com-

mand with no data, usually

used for one-shot command

S = START CONDITION

P = STOP CONDITION

SHADED = SLAVE TRANSMISSION

/// = NOT ACKNOWLEDGED

ADDRESS RD ACK DATA ///

P

7 bits

8 bits

Data Byte: reads data from

the register commanded

by the last read byte or

write byte transmission;

also used for SMBus alert

response return address

Figure 1. SMBus Protocols

6 _______________________________________________________________________________________

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