19-3344; Rev 2; 10/08
KIT
ATION
EVALU
E
BL
AVAILA
2-Channel Temperature Monitor with Dual
Automatic PWM Fan-Speed Controller
General Description
The MAX6640 monitors its own temperature and one
external diode-connected transistor or the temperatures
of two external diode-connected transistors, typically
available in CPUs, FPGAs, or GPUs. 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. Temperature data
can be read at any time over the SMBus, and three pro-
grammable alarm outputs can be used to generate
interrupts, throttle signals, or overtemperature shut-
down signals.
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. Speed control is
accomplished by tachometer feedback from the fan, so
that the speed of the fan is controlled, not just the PWM
duty cycle. Accuracy of speed measurement is ±4%.
The MAX6640 is available in 16-pin QSOP and 16-pin
TQFN 5mm x 5mm packages. It operates from 3.0V to
3.6V and consumes just 500μA of supply current.
Features
♦
Two Thermal-Diode Inputs
♦
Local Temperature Sensor
♦
1°C Remote Temperature Accuracy (+60°C to
+100°C)
♦
Two PWM Outputs for Fan Drive (Open Drain; can
be Pulled Up to +13.5V)
♦
Programmable Fan-Control Characteristics
♦
Automatic Fan Spin-Up Ensures Fan Start
♦
Controlled Rate-of-Change Ensures Unobtrusive
Fan-Speed Adjustments
♦
±4% Fan-Speed Measurement Accuracy
♦
Temperature Monitoring Begins at POR for Fail-
Safe System Protection
♦
OT
and
THERM
Outputs for Throttling or
Shutdown
♦
Measures Temperatures Up to +150°C
♦
Tiny 5mm x 5mm 16-Pin TQFN and QSOP
Packages
MAX6640
Applications
Desktop Computers
Notebook Computers
Workstations
Servers
Networking Equipment
SMBus is a trademark of Intel Corp.
Typical Operating Circuit appears at end of data sheet.
MAX6640ATE+
MAX6640AEE+
PART
Ordering Information
OPERATING MEASUREMENT PIN-
RANGE
RANGE
PACKAGE
-40°C to
+125°C
-40°C to
+125°C
0°C to +150°C
0°C to +150°C
16 QSOP
16 TQFN-EP*
+Denotes
a lead-free/RoHS-compliant package.
*EP
= Exposed pad.
Pin Configurations
TACH1
PWM1
SDA
14
TOP VIEW
PWM1 1
TACH1 2
PWM2 3
TACH2 4
FANFAIL 5
THERM 6
OT 7
V
CC
8
+
16 SCL
15 SDA
14 ALERT
PWM2
TACH2
FANFAIL
THERM
+
16
15
13
1
2
3
4
*CONNECT EXPOSED
PAD TO GND
5
OT
6
V
CC
7
GND
8
DXP1
SCL
12
ALERT
I.C.
DXP2
DXN
MAX6640
13 I.C.
12 DXP2
11 DXN
10 GND
9
DXP1
MAX6640
11
10
9
QSOP
5mm x 5mm THIN QFN
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
2-Channel Temperature Monitor with Dual
Automatic PWM Fan-Speed Controller
MAX6640
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ..............................................................-0.3V to +6V
PWM1, PWM2, TACH1, and TACH2 to GND ......-0.3V to +13.5V
DXP1 and DXP2 to GND ..........................-0.3V to +(V
CC
+ 0.3V)
DXN to GND ..........................................................-0.3V to +0.8V
SCL, SDA,
THERM, OT, FANFAIL,
and
ALERT
to GND..............................................-0.3V to +6V
SDA,
OT, THERM, ALERT, FANFAIL,
PWM1, and PWM2 Current .............................-1mA to +50mA
DXN Current .......................................................................±1mA
ESD Protection (all pins, Human Body Model)..................2000V
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derated 8.3mW/°C above +70°C)....... 667mW
16-Pin TQFN 5mm x 5mm
(derated at 33.3mW/°C above +70°C)................2666.7mW
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 +3.6V, T
A
= 0°C to +125°C, unless otherwise noted. Typical values are at V
CC
= +3.3V, T
A
= +85°C.) (Note 1)
PARAMETER
Operating Supply Voltage Range
Standby Current
Operating Current
SYMBOL
V
CC
SMB static, sleep mode
Interface inactive, ADC active
V
CC
= +3.3V, +60°C
≤
T
A
≤
+100°C and
+60°C
≤
T
R
≤
+100°C
External Temperature Error
V
CC
= +3.3V, +40°C
≤
T
A
≤
+100°C and
0°C
≤
T
R
≤
+145°C
V
CC
= +3.3V,
0°C
≤
T
R
≤
+145°C
V
CC
= +3.3V,
+25°C
≤
T
A
≤
+100°C
V
CC
= +3.3V,
0°C
≤
T
A
≤
+125°C
Supply Sensitivity of Temperature
Measurement
Temperature Resolution
Conversion Time
Conversion-Rate Timing Error
PWM Frequency Error
Tachometer Accuracy
Remote-Diode Sourcing Current
DXN Source Voltage
V
CC
= 3.135V to 3.345V,
+60°C
≤
T
A
≤
+85°C
High level
Low level
70
7.0
100
10
0.7
-10
-10
±0.2
+0.125
11
125
+10
+10
±4
130
13.0
CONDITIONS
MIN
+3.0
3
0.5
TYP
MAX
+3.6
10
1
±1
±2.5
±3.8
±2
°C
±4
°C/V
°C
Bits
ms
%
%
%
μA
V
°C
UNITS
V
μA
mA
Internal Temperature Error
2
_______________________________________________________________________________________
2-Channel Temperature Monitor with Dual
Automatic PWM Fan-Speed Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.0V to +3.6V, T
A
= 0°C to +125°C, unless otherwise noted. Typical values are at V
CC
= +3.3V, T
A
= +85°C.) (Note 1)
PARAMETER
DIGITAL INPUTS AND OUTPUTS
Output Low Voltage (Sink
Current) (OT,
ALERT, FANFAIL,
THERM,
SDA, PWM1, and PWM2)
Output High Leakage Current
(OT,
ALERT, FANFAIL, THERM,
SDA, PWM1, and PWM2)
Logic-Low Input Voltage (SDA,
SCL,
THERM,
TACH1, TACH2)
Logic-High Input Voltage (SDA,
SCL,
THERM,
TACH1, TACH2)
Input Leakage Current (SDA,
SCL,
THERM,
TACH1, TACH2)
Input Capacitance
SMBus TIMING
(Note 2)
Serial Clock Frequency
Clock Low Period
Clock High Period
Bus Free Time Between Stop and
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
f
SCL
t
LOW
t
HIGH
t
BUF
t
SU:STA
t
HD:STO
t
SU:STO
t
SU:DAT
t
HD:DAT
t
F
t
R
t
TIMEOUT
58
74
90% of SMBCLK to 90% of SMBDATA
10% of SDA to 10% of SCL
90% of SCL to 10% of SDA
10% of SDA to 10% of SCL
10% of SCL to 10% of SDA (Note 4)
(Note 3)
10% to 10%
90% to 90%
10
4
4.7
4.7
4.7
4
4
250
300
300
1000
90
100
kHz
μs
μs
μs
μs
μs
μs
ns
ns
ns
ns
ms
C
IN
V
OL
ALERT, FANFAIL, THERM, OT
SDA I
SINK
= 6mA
PWM1, PWM2, I
SINK
= 4mA
I
OH
0.4
0.4
1
μA
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX6640
V
IL
0.8
V
V
IH
V
CC
= 3.3V
V
IN
= V
CC
or GND
2.1
1
5
V
μA
pF
Note 1:
Note 2:
Note 3:
Note 4:
All parameters tested at a single temperature. Specifications are guaranteed by design.
Timing specifications guaranteed by design.
The serial interface resets when SCL is low for more than t
TIMEOUT
.
A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCL's falling edge.
_______________________________________________________________________________________
3
2-Channel Temperature Monitor with Dual
Automatic PWM Fan-Speed Controller
MAX6640
Typical Operating Characteristics
(V
CC
= 3.3V, T
A
= +25°C.)
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6640 toc01
OPERATING SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6640 toc02
REMOTE TEMPERATURE ERROR
vs. REMOTE-DIODE TEMPERATURE
MAX6640 toc03
10
9
8
SUPPLY CURRENT (µA)
7
6
5
4
3
2
1
0
3.0
3.5
4.0
4.5
5.0
800
700
SUPPLY CURRENT (µA)
600
500
400
300
2
TEMPERATURE ERROR (°C)
1
0
-1
FAIRCHILD 2N3906
200
5.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
-2
0
25
50
75
100
125
TEMPERATURE (°C)
LOCAL TEMPERATURE ERROR
vs. DIE TEMPERATURE
MAX6640 toc04
REMOTE TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
MAX6640 toc05
LOCAL TEMPERATURE ERROR
vs. POWER-SUPPLY NOISE FREQUENCY
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
V
IN
= 250mV
P-P
SQUARE WAVE APPLIED TO
V
CC
WITH NO BYPASS CAPACITOR
MAX6640 toc06
1.0
0.5
TEMPERATURE ERROR (°C)
0
-0.5
-1.0
-1.5
-2.0
0
25
50
75
100
2.0
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
V
IN
= 250mV
P-P
SQUARE WAVE APPLIED TO
V
CC
WITH NO BYPASS CAPACITOR
2.0
125
10
100
1k
FREQUENCY (Hz)
10k
100k
1
10
100
1k
10k
100k
TEMPERATURE (°C)
FREQUENCY (Hz)
REMOTE TEMPERATURE ERROR
vs. COMMON-MODE NOISE FREQUENCY
MAX6640 toc07
REMOTE TEMPERATURE ERROR
vs. DIFFERENTIAL NOISE FREQUENCY
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
V
IN
= AC-COUPLED TO DXP
V
IN
= 100mV
P-P
SQUARE WAVE
MAX6640 toc08
TEMPERATURE ERROR
vs. DXP-DXN CAPACITANCE
1.0
TEMPERATURE ERROR (°C)
0
-1.0
-2.0
-3.0
-4.0
-5.0
-6.0
MAX6640 toc09
2.0
1.5
TEMPERATURE ERROR (°C)
1.0
0.5
0
-0.5
-1.0
-1.5
-2.0
V
IN
= AC-COUPLED TO DXP AND DXN
V
IN
= 100mV
P-P
SQUARE WAVE
2.0
2.0
0.1
1
10
100
1k
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
0.1
1
10
100
FREQUENCY (Hz)
DXP-GND CAPACITANCE (nF)
4
_______________________________________________________________________________________
2-Channel Temperature Monitor with Dual
Automatic PWM Fan-Speed Controller
Typical Operating Characteristics (continued)
(V
CC
= 3.3V, T
A
= +25°C.)
PWMOUT FREQUENCY
vs. DIE TEMPERATURE
MAX6640 toc10
MAX6640
PWMOUT FREQUENCY
vs. SUPPLY VOLTAGE
MAX6640 toc11
35
35
PWMOUT FREQUENCY (Hz)
33
PWMOUT FREQUENCY (Hz)
-40
-15
10
35
60
85
110
34
34
33
32
32
31
31
30
TEMPERATURE (°C)
30
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
Pin Description
PIN
TQFN-EP
1, 15
QSOP
3, 1
NAME
PWM2,
PWM1
TACH2,
TACH1
FANFAIL
THERM
OT
V
CC
GND
DXP1,
DXP2
DXN
I.C.
ALERT
SCL
SDA
EP
FUNCTION
Open-Drain Output to Power Transistor Driving Fan. Connect to the gate of a MOSFET or base of a
bipolar transistor. PWM_ requires a pullup resistor. The pullup resistor can be connected to a
supply voltage as high as 13.5V, regardless of the MAX6640’s supply voltage.
Tachometer Inputs. Connect to the tachometer output of the fan. TACH_ requires a pullup resistor.
The pullup resistor can be connected to a supply voltage as high as 13.5V, regardless of the
MAX6640’s supply voltage.
Active-Low, Open-Drain, Fan-Failure Output. Open circuit when V
CC
= 0.
Active-Low, Open-Drain Thermal Alarm Output. Typically used for clock throttling. Open circuit
when V
CC
= 0.
Active-Low, Open-Drain Overtemperature Output. Typically used for system shutdown or clock
throttling. Can be pulled up to 5.5V regardless of V
CC
. Open circuit when V
CC
= 0.
Power-Supply Input. 3.3V nominal. Bypass V
CC
to GND with a 0.1μF capacitor.
Ground. Connect to a clean ground reference.
Combined Current Source and A/D Positive Input for Remote Diode. Connect to anode of remote-
diode-connected temperature-sensing transistor. Do not leave unconnected; connect to DXN if no
remote diode is used. Place a 2200pF capacitor between DXP_ and DXN for noise filtering.
Combined Current Sink and A/D Negative Input for Remote Diode. Connect cathode of the remote-
diode-connected transistor to DXN.
Internally Connected. Connect to V
CC
.
Active-Low, Open-Drain SMBus Alert Output
SMBus Serial-Clock Input. Can be pulled up to 5.5V regardless of V
CC
. Open circuit when V
CC
= 0.
SMBus Serial-Data Input/Output, Open Drain. Can be pulled up to 5.5V regardless of V
CC
. Open
circuit when V
CC
= 0.
Exposed Pad (TQFN package only). Internally connected to GND. Connect to a large ground
plane to maximize thermal performance. Not intended as an electrical connection point.
2, 16
3
4
5
6
7
8, 10
4, 2
5
6
7
8
10
9, 12
9
11
12
13
14
—
11
13
14
16
15
—
_______________________________________________________________________________________
5
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