Rainbow Electronics MAX6641 User Manual

General Description

The MAX6641 temperature sensor and fan controller
accurately measures the temperature of its own die and
the temperature of a remote pn junction. The device
reports temperature values in digital form using a 2-wire
serial interface. The remote pn junction is typically the
emitter-base junction of a common-collector pnp on a
CPU, FPGA, or ASIC.

The 2-wire serial interface accepts standard System
Management Bus (SMBus)TMwrite byte, read byte,
send byte, and receive byte commands to read the
temperature data and program the alarm thresholds.
The temperature data controls a PWM output signal to
adjust the speed of a cooling fan, thereby minimizing
noise when the system is running cool, but providing
maximum cooling when power dissipation increases.
The device also features an over-temperature alarm
output to generate interrupts, throttle signals, or shut
down signals. The MAX6641 operates from supply volt­ages in the 3.0V to 5.5V range and typically consumes
500µA of supply current.

The MAX6641 is available in a slim 10-pin µMAX®pack­age and is available over the automotive temperature
range (-40°C to +125°C).

Applications

Desktop Computers

Notebook Computers

Workstations

Servers

Networking Equipment

Industrial

Features

♦ Tiny 3mm x 5mm µMAX Package

♦ Thermal Diode Input

♦ Local Temperature Sensor

♦ Open-Drain PWM Output for Fan Drive

♦ Programmable Fan Control Characteristics

♦ Automatic Fan Spin-Up Ensures Fan Start

♦ ±1°C Remote Temperature Accuracy (+60°C to

+145°C)

♦ Controlled Rate of Change Ensures Unobtrusive

Fan-Speed Adjustments

♦ Temperature Monitoring Begins at Power-On for

Fail-Safe System Protection

♦ OT Output for Throttling or Shutdown

MAX6641

SMBus-Compatible Temperature Monitor with

Automatic PWM Fan-Speed Controller

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3304; Rev 0; 5/04

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.

PART

TEMP RANGE

PIN-

SMBus

ADDRESS

MAX6641AUB90

-40°C to
+125°C

10 µMAX

1001 000x

MAX6641AUB92

-40°C to
+125°C

10 µMAX

1001 001x

MAX6641AUB94

-40°C to
+125°C

10 µMAX

1001 010x

MAX6641AUB96

-40°C to
+125°C

10 µMAX

1001 011x

1

2

3

4

5

10

9

8

7

6

PWMOUT

V

CC

SMBDATA

SMBCLKGND

DXP

DXN

I.C.

MAX6641

µMAX

TOP VIEW

I.C.OT

Pin Configuration

µMAX is a registered trademark of Maxim Integrated Products, Inc.

SMBus is a trademark of Intel Corp.

Typical Application Circuit appears at end of data sheet.

PACKAGE

MAX6641

SMBus-Compatible Temperature Monitor with
Automatic PWM Fan-Speed Controller

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +3.0V to +5.5V, TA= 0°C to +125°C, unless otherwise noted. Typical values are at VCC= 3.3V, TA= +25°C.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

All Voltages Referenced to GND
V

CC

, OT, SMBDATA, SMBCLK, PWMOUT...............-0.3V to +6V

DXP.........................................................…-0.3V to (V

CC

+ 0.3V)

DXN ......................................................................-0.3V to +0.8V

ESD Protection

(all pins, Human Body Model) ......…………………….±2000V

Continuous Power Dissipation (T

A

= +70°C)

10-Pin µMAX (derate 5.6mW/°C above +70°C) .......... 444mW

Operating Temperature Range .........................-40°C to +125°C

Junction Temperature......................................................+150°C

Storage Temperature Range ............................-65°C to +150°C

Lead Temperature (soldering, 10s) ............................... +300°C

PARAMETER

CONDITIONS

UNITS

Operating Supply Voltage Range

V

CC

3.0 5.5 V

Operating Current SMBDATA, SMBCLK not switching 0.5 1 mA

+25°C ≤ TR ≤ +125°C,
T

A

= +60°C

±1

0°C ≤ TR ≤ +145°C,
+25°C ≤ T

A

= ≤ +100°C

±3

External Temperature Error

0°C ≤ TR ≤ +145°C,
0°C ≤ T

A

≤ +125°C

±4

°C

+25°C ≤ TA ≤ +100°C

Internal Temperature Error

0°C ≤ TA ≤ +125°C -4 +4

°C

1°C

Temperature Resolution

8 Bits

Conversion Time 200

300 ms

PWM Frequency Tolerance -20

%

High level 80

120

Remote-Diode Sourcing Current

Low level 8 10 12

µA

DXN Source Voltage 0.7 V

I/O

OT, SMBDATA, PWMOUT Output
Low Voltage

V

OL

I

OUT

= 6mA 0.4 V

OT, SMBDATA, PWMOUT
Output-High Leakage Current

I

OH

VCC = 5.5V 1 µA

SMBDATA, SMBCLK Logic-Low
Input Voltage

V

IL

VCC = 3V to 5.5V 0.8 V

SMBDATA, SMBCLK Logic-High
Input Voltage

V

IH

VCC = 3V to 5.5V 2.1 V

SMBDATA, SMBCLK Leakage
Current

1µA

SMBDATA, SMBCLK Input
Capacitance

C

IN

5pF

SYMBOL

VCC = 3.3V

VCC = 3.3V

MIN TYP MAX

-2.5 +2.5

250

100

+20

MAX6641

SMBus-Compatible Temperature Monitor with

Automatic PWM Fan-Speed Controller

_______________________________________________________________________________________ 3

Note 1: Timing specifications guaranteed by design.
Note 2: The serial interface resets when SMBCLK is low for more than t

TIMEOUT

.

Note 3: A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SMBCLK’s falling edge.

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3.0V to +5.5V, TA= 0°C to +125°C, unless otherwise noted. Typical values are at VCC= 3.3V, TA= +25°C.)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

SMBus-COMPATIBLE TIMING (Note 1) (See Figures 2, 3)

Serial Clock Frequency f

SCLK

(Note 2) 100 kHz

Clock Low Period t

LOW

10% to 10% 4 µs

Clock High Period t

HIGH

90% to 90% 4.7 µs

Bus Free Time Between Stop and
Start Condition

t

BUF

4.7 µs

Hold Time After (Repeated) Start
Condition

4µs

S M Bus S tar t C ond i ti on S etup Ti m e

t

SU:STA

90% of SMBCLK to 90% of SMBDATA 4.7 µs

Start Condition Hold Time

10% of SMBDATA to 10% of SMBCLK 4 µs

Stop Condition Setup Time

90% of SMBCLK to 10% of SMBDATA 4 µs

Data Setup Time

10% of SMBDATA to 10% of SMBCLK 250 ns

Data Hold Time

10% of SMBCLK to 10% of SMBDATA
(Note 3)

300 ns

SMBus Fall Time t

F

300 ns

SMBus Rise Time t

R

ns

SMBus Timeout

29 37 55 ms

Startup Time After POR t

POR

500 ms

Typical Operating Characteristics

(VCC= 3.3V, TA= +25°C, unless otherwise noted.)

OPERATING SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX6641 toc01

SUPPLY VOLTAGE (V)

OPERATING SUPPLY CURRENT (µA)

5.04.54.03.5

350

400

450

500

550

600

300

3.0 5.5

NO SMBus ACTIVITY

REMOTE TEMPERATURE ERROR

vs. REMOTE-DIODE TEMPERATURE

MAX6641 toc02

TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

1007525 50

-1.5

-1.0

-0.5

0

0.5

1.0

1.5

2.0

-2.0
0125

LOCAL TEMPERATURE ERROR

vs. DIE TEMPERATURE

MAX6641 toc03

TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

100755025

-1

0

1

2

-2
0125

t

HD:STA

t

HD:STO

t

SU:STO

t

SU:DAT

t

HD:DAT

t

TIMEOUT

1000

MAX6641

SMBus-Compatible Temperature Monitor with
Automatic PWM Fan-Speed Controller

4 _______________________________________________________________________________________

REMOTE TEMPERATURE ERROR

vs. POWER-SUPPLY NOISE FREQUENCY

MAX6641 toc04

FREQUENCY (kHz)

TEMPERATURE ERROR (°C)

100101

-1.25

-1.00

-0.75

-0.50

-0.25

0

-1.50

0.1 1000

TA = +80°C, 250mV SQUARE WAVE APPLIED
AT V

CC

, NO BYPASS CAPACITOR

LOCAL TEMPERATURE ERROR

vs. POWER-SUPPLY NOISE FREQUENCY

MAX6641 toc05

FREQUENCY (kHz)

TEMPERATURE ERROR (°C)

100101

-1.5

-1.0

-0.5

0

0.5

1.0

-2.0

0.1 1000

TA = +25°C, 250mV SQUARE WAVE APPLIED
AT V

CC

, NO BYPASS CAPACITOR

REMOTE TEMPERATURE ERROR

vs. COMMON-MODE NOISE FREQUENCY

MAX6641 toc06

FREQUENCY (kHz)

TEMPERATURE ERROR (°C)

100101

-1.0

-0.5

0

0.5

1.0

-1.5

0.1 1000

TA = +80°C, VIN = 100mV

P-P

SQUARE WAVE APPLIED TO DXP

REMOTE TEMPERATURE ERROR

vs. DIFFERENTIAL-MODE NOISE FREQUENCY

MAX6641 toc07

FREQUENCY (kHz)

TEMPERATURE ERROR (°C)

100101

-0.5

0

0.5

1.0

1.5

-1.0

0.1 1000

TA = +80°C, VIN = 10mV

P-P

SQUARE WAVE APPLIED
TO DXP - DXN

REMOTE TEMPERATURE ERROR

vs. DXP - DXN CAPACITANCE

MAX6641 toc08

DXP - DXN CAPACITANCE (nF)

NORMALIZED TEMPERATURE ERROR (°C)

101

-4

-3

-2

-1

0

1

2

3

-5

0.1 100

TA = +80°C

PWM FREQUENCY ERROR

vs. DIE TEMPERATURE

MAX6641 toc09

TEMPERATURE (°C)

PWM FREQUENCY ERROR (Hz)

1007550250-25

-2

-1

0

1

2

-3

-50 125

PWM FREQUENCY ERROR

vs. SUPPLY VOLTAGE

MAX6641 toc10

SUPPLY VOLTAGE (V)

PWM FREQUENCY ERROR (Hz)

5.04.54.03.5

-0.5

0

0.5

1.0

1.5

2.0

-1.0

3.0 5.5

TA = +25°C

Typical Operating Characteristics (continued)

(VCC= 3.3V, TA= +25°C, unless otherwise noted.)

Detailed Description

The MAX6641 temperature sensor and fan controller
accurately measures the temperature of its own die and
the temperature of a remote pn junction. The device
reports temperature values in digital form using a 2­wire serial interface. The remote pn junction is typically
the emitter-base junction of a common-collector pnp on
a CPU, FPGA, or ASIC. The MAX6641 operates from
supply voltages of 3.0V to 5.5V and consumes 500µA
of supply current. The temperature data controls a
PWM output signal to adjust the speed of a cooling fan.
The device also features an over-temperature alarm
output to generate interrupts, throttle signals, or shut
down signals.

SMBus Digital Interface

From a software perspective, the MAX6641 appears as
a set of byte-wide registers that contain temperature
data, alarm threshold values, and control bits. A stan­dard SMBus-compatible 2-wire serial interface is used
to read temperature data and write control bits and
alarm threshold data. These devices respond to the
same SMBus slave address for access to all functions.

The MAX6641 employs four standard SMBus protocols:
write byte, read byte, send byte, and receive byte
(Figures 1, 2, and 3). The shorter receive byte protocol
allows quicker transfers, provided that the correct data
register was previously selected by a read byte instruc­tion. Use caution when using the shorter protocols in
multimaster systems, as a second master could over­write the command byte without informing the first mas­ter. The MAX6641 has four different slave addresses
available; therefore, a maximum of four MAX6641
devices can share the same bus.

Temperature data within the 0°C to +255°C range can
be read from the read external temperature register
(00h). Temperature data within the 0°C to +125°C range
can be read from the read internal temperature register
(01h). The temperature data format for these registers is
8 bits, with the LSB representing +1°C (Table 1) and the
MSB representing +128°C. The MSB is transmitted first.
All values below 0°C are clipped to 00h.

Table 1 details the register address and function,

whether they can be read or written to, and the power-on
reset (POR) state. See Tables 1–5 for all other register
functions and the Register Descriptions section. Figure 4
is the MAX6641 block diagram.

MAX6641

SMBus-Compatible Temperature Monitor with

Automatic PWM Fan-Speed Controller

_______________________________________________________________________________________ 5

PIN NAME FUNCTION

1, 6 I.C. Internally Connected. Must be connected to GND.

2DXN

Combined Remote-Diode Cathode Connection and A/D Negative Input. Connect the cathode of the
remote-diode-connected transistor to DXN.

3 DXP

Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode Channel. Connect
DXP to the anode of a remote-diode-connected temperature-sensing transistor. DO NOT LEAVE
DXP FLOATING; connect to DXN if no remote diode is used. Place a 2200pF capacitor between DXP
and DXN for noise filtering.

4 GND Ground

5 OT

Active-Low, Open-Drain, Over-Temperature Output. Use OT as an interrupt, a system shutdown
signal, or to control clock throttling. OT can be pulled up to 5.5V, regardless of the voltage on VCC.
OT is high impedance when V

CC

= 0.

7 SMBCLK

SMBus Serial Clock Input. SMBCLK can be pulled up to 5.5V, regardless of V

CC

. Open drain.

SMBCLK is high impedance when V

CC

= 0.

8

SMBus Serial Data Input/Output. SMBDATA can be pulled up to 5.5V, regardless of VCC. Open drain.
SMBDATA is high impedance when V

CC

= 0.

9VCCPositive Supply. Bypass with a 0.1µF capacitor to GND.

10

PWM Output to Fan Power Transistor. Connect PWMOUT to the gate of a MOSFET or the base of a
bipolar transistor to drive the fan’s power supply with a PWM waveform. Alternatively, the PWM output
can be connected to the PWM input of a fan with direct speed-control capability, or it can be
converted to a DC voltage for driving the fan’s power supply. PWMOUT requires a pullup resistor. The
pullup resistor can be connected to a voltage supply up to 5.5V, regardless of V

CC

.

Pin Description

SMBDATA

PWMOUT

MAX6641

SMBus-Compatible Temperature Monitor with
Automatic PWM Fan-Speed Controller

6 _______________________________________________________________________________________

READ/

WRITE

REGISTER

POR

FUNCTION/

NAME

D7 D6 D5 D4 D3 D2 D1

D0

R 00h

Read remote

(external)

MSB

(+32°C)

LSB

(+1°C)

R 01h

Read local

(internal)

MSB

(+32°C)

LSB

(+1°C)

R/W

02h

Configuration

byte

Reserved
set to 0

Timeout: 0 =

Fan

PWM

Min duty

1 = fan-

Spin-up

XX

R/W

03h

Remote-diode

temperature

OT limit

MSB

(+32°C)

LSB

(+1°C)

R/W

04h

Local-diode
temperature

OT limit

MSB

(+32°C)

LSB

(+1°C)

R 05h

OT status

Remote 1

fault

XXXXXX

R/W

06h

OT mask

Remote 1

XXXXXX

R/W

07h

0110 000x

Fan-start duty

cycle

MSB

LSB

X

R/W

08h

1111 000x

(240 =

Fan maximum

MSB

(32/240)

LSB

X

R/W

09h

cycle

MSB

(32/240)

LSB

X

R 0Ah

Fan

instantaneous

MSB

(32/240)

LSB

X

R/W

0Bh

Remote-diode

fan-start

MSB

(+32°C)

LSB

(+1°C)

Table 1. Register Functions

ADDRESS

STATE

0000 0000

0000 0000

0000 00xx

0110 1110

0101 0000

00xx xxxx

00xx xxxx

(96 = 40%)

temperature

temperature

(+128°C)

(+128°C)

(+128°C)

(+128°C)

= fault

= masked

(128/240)

(+64°C)

(+64°C)

Reserved

set to 0

(+64°C)

(+64°C)

Local 1 =

Local 1 =

masked

(64/240) (32/240) ( 16/240) (8/240) (4/240)

enabled, 1 =

disabled

(+16°C) (+8°C) (+4°C) (+2°C)

(+16°C) (+8°C) (+4°C) (+2°C)

cycle:

0 = 0%,

invert

(+16°C) (+8°C) (+4°C) (+2°C)

(+16°C) (+8°C) (+4°C) (+2°C)

start duty

disable

cycle

(2/240)

100%)

0000 000x

0000 000x

0000 0000

duty cycle

Fan target duty

duty cycle

temperature

(128/240)

(128/240)

(128/240)

(+128°C)

(64/240)

(64/240)

(64/240)

(+64°C)

( 16/240) (8/240) (4/240)

( 16/240) (8/240) (4/240)

( 16/240) (8/240) (4/240)

(+16°C) (+8°C) (+4°C) (+2°C)

(2/240)

(2/240)

(2/240)