19-3304; Rev 1; 4/06
SMBus-Compatible Temperature Monitor with
Automatic PWM Fan-Speed Controller
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)
TM
write 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 volt-
ages 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
®
pack-
age and is available over the -40°C to +125°C automo-
tive temperature range.
♦
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
Features
MAX6641
Ordering Information
PART
PIN-
PACKAGE
10 µMAX
10 µMAX
10 µMAX
10 µMAX
SMBus
ADDRESS
1001 000x
1001 001x
1001 010x
1001 011x
PKG
CODE
U10-2
U10-2
U10-2
U10-2
Applications
Desktop Computers
Notebook Computers
Workstations
Servers
Networking Equipment
Industrial
MAX6641AUB90
MAX6641AUB92
MAX6641AUB94
MAX6641AUB96
Note:
All devices are specified over the -40°C to +125°C tem-
perature range.
Pin Configuration
TOP VIEW
Typical Application Circuit appears at end of data sheet.
I.C. 1
DXN
DXP
GND
OT
2
3
4
5
10 PWMOUT
9
V
CC
SMBDATA
SMBCLK
I.C.
MAX6641
8
7
6
µMAX is a registered trademark of Maxim Integrated Products, Inc.
SMBus is a trademark of Intel Corp.
µMAX
________________________________________________________________
Maxim Integrated Products
1
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.
SMBus-Compatible Temperature Monitor with
Automatic PWM Fan-Speed Controller
MAX6641
ABSOLUTE MAXIMUM RATINGS
(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
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.
ELECTRICAL CHARACTERISTICS
(V
CC
= +3.0V to +5.5V, T
A
= 0°C to +125°C, unless otherwise noted. Typical values are at V
CC
= 3.3V, T
A
= +25°C.)
PARAMETER
Operating Supply Voltage Range
Operating Current
SYMBOL
V
CC
SMBDATA, SMBCLK not switching
+25°C
≤
T
R
≤
+125°C,
T
A
= +60°C
External Temperature Error
V
CC
= 3.3V
0°C
≤
T
R
≤
+145°C,
+25°C
≤
T
A
=
≤
+100°C
0°C
≤
T
R
≤
+145°C,
0°C
≤
T
A
≤
+125°C
Internal Temperature Error
Temperature Resolution
Conversion Time
PWM Frequency Tolerance
Remote-Diode Sourcing Current
DXN Source Voltage
I/O
OT,
SMBDATA, PWMOUT Output
Low Voltage
OT,
SMBDATA, PWMOUT
Output-High Leakage Current
SMBDATA, SMBCLK Logic-Low
Input Voltage
SMBDATA, SMBCLK Logic-High
Input Voltage
SMBDATA, SMBCLK Leakage
Current
SMBDATA, SMBCLK Input
Capacitance
C
IN
5
V
OL
I
OH
V
IL
V
IH
I
OUT
= 6mA
V
CC
= 5.5V
V
CC
= 3V to 5.5V
V
CC
= 3V to 5.5V
2.1
1
0.4
1
0.8
V
µA
V
V
µA
pF
High level
Low level
V
CC
= 3.3V
+25°C
≤
T
A
≤
+100°C
0°C
≤
T
A
≤
+125°C
-3
-4
1
8
200
-20
80
8
100
10
0.7
250
300
+20
120
12
CONDITIONS
MIN
3.0
0.5
TYP
MAX
5.5
1
±1
±3
±4
+3
+4
°C
°C
Bits
ms
%
µA
V
°C
UNITS
V
mA
2
_______________________________________________________________________________________
SMBus-Compatible Temperature Monitor with
Automatic PWM Fan-Speed Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.0V to +5.5V, T
A
= 0°C to +125°C, unless otherwise noted. Typical values are at V
CC
= 3.3V, T
A
= +25°C.)
PARAMETER
Serial-Clock Frequency
Clock Low Period
Clock High Period
Bus Free Time Between Stop and
Start Condition
Hold Time After (Repeated) Start
Condition
SMBus Start Condition Setup Time
Start Condition Hold Time
Stop Condition Setup Time
Data Setup Time
Data Hold Time
SMBus Fall Time
SMBus Rise Time
SMBus Timeout
Startup Time After POR
SYMBOL
f
SCLK
t
LOW
t
HIGH
t
BUF
t
HD:STA
t
SU:STA
t
HD:STO
t
SU:STO
t
SU:DAT
t
HD:DAT
t
F
t
R
t
TIMEOUT
t
POR
29
37
90% of SMBCLK to 90% of SMBDATA
10% of SMBDATA to 10% of SMBCLK
90% of SMBCLK to 10% of SMBDATA
10% of SMBDATA to 10% of SMBCLK
10% of SMBCLK to 10% of SMBDATA
(Note 3)
(Note 2)
10% to 10%
90% to 90%
4
4.7
4.7
4
4.7
4
4
250
300
300
1000
55
500
CONDITIONS
MIN
TYP
MAX
100
UNITS
kHz
µs
µs
µs
µs
µs
µs
µs
ns
ns
ns
ns
ms
ms
MAX6641
SMBus-COMPATIBLE TIMING
(Note 1) (See Figures 2, 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.
Typical Operating Characteristics
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
OPERATING SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6641 toc01
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
-2
0
25
50
75
100
125
0
MAX6641 toc02
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6641 toc03
600
NO SMBus ACTIVITY
OPERATING SUPPLY CURRENT (µA)
550
500
450
400
350
300
3.0
3.5
4.0
4.5
5.0
2.0
2
TEMPERATURE ERROR (°C)
1
0
-1
5.5
25
50
75
100
125
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
3
SMBus-Compatible Temperature Monitor with
Automatic PWM Fan-Speed Controller
MAX6641
Typical Operating Characteristics (continued)
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
REMOTE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6641 toc04
LOCAL TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6641 toc05
REMOTE TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
T
A
= +80°C, V
IN
= 100mV
P-P
SQUARE WAVE APPLIED TO DXP
TEMPERATURE ERROR (°C)
0.5
MAX6641 toc06
0
-0.25
TEMPERATURE ERROR (°C)
-0.50
-0.75
-1.00
-1.25
-1.50
T
A
= +80°C, 250mV SQUARE WAVE APPLIED
AT V
CC
, NO BYPASS CAPACITOR
1.0
0.5
TEMPERATURE ERROR (°C)
0
-0.5
-1.0
-1.5
-2.0
T
A
= +25°C, 250mV SQUARE WAVE APPLIED
AT V
CC
, NO BYPASS CAPACITOR
1.0
0
-0.5
-1.0
-1.5
0.1
1
10
FREQUENCY (kHz)
100
1000
0.1
1
10
FREQUENCY (kHz)
100
1000
0.1
1
10
FREQUENCY (kHz)
100
1000
REMOTE TEMPERATURE ERROR
vs. DIFFERENTIAL-MODE NOISE FREQUENCY
NORMALIZED TEMPERATURE ERROR (°C)
T
A
= +80°C, V
IN
= 10mV
P-P
SQUARE WAVE APPLIED
TO DXP - DXN
MAX6641 toc07
REMOTE TEMPERATURE ERROR
vs. DXP - DXN CAPACITANCE
2
1
0
-1
-2
-3
-4
-5
T
A
= +80°C
0.1
1
10
100
MAX6641 toc08
1.5
3
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
0.1
1
10
FREQUENCY (kHz)
100
1000
DXP - DXN CAPACITANCE (nF)
PWM FREQUENCY ERROR
vs. DIE TEMPERATURE
MAX6641 toc09
PWM FREQUENCY ERROR
vs. SUPPLY VOLTAGE
MAX6641 toc10
2
2.0
1.5
1.0
0.5
0
-0.5
T
A
= +25°C
-1.0
PWM FREQUENCY ERROR (Hz)
0
-1
-2
-3
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
PWM FREQUENCY ERROR (Hz)
1
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
SMBus-Compatible Temperature Monitor with
Automatic PWM Fan-Speed Controller
MAX6641
Pin Description
PIN
1, 6
2
NAME
I.C.
DXN
FUNCTION
Internally Connected. Must be connected to GND.
Combined Remote-Diode Cathode Connection and A/D Negative Input. Connect the cathode of the
remote-diode-connected transistor to DXN.
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.
Ground
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 V
CC
.
OT
is high impedance when V
CC
= 0.
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.
SMBus Serial-Data Input/Output. SMBDATA can be pulled up to 5.5V, regardless of V
CC
. Open drain.
SMBDATA is high impedance when V
CC
= 0.
Positive Supply. Bypass with a 0.1µF capacitor to GND.
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
.
3
DXP
4
5
GND
OT
7
8
9
SMBCLK
SMBDATA
V
CC
10
PWMOUT
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 2-wire serial interface. The remote pn junction is typi-
cally 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 stan-
dard 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 instruc-
tion. Use caution when using the shorter protocols in
multimaster systems, as a second master could over-
write the command byte without informing the first mas-
ter. 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.
5
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