19-3305; Rev 1; 8/04
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
General Description
The MAX6643/MAX6644/MAX6645 monitor temperature
and automatically adjust fan speed to ensure optimum
cooling while minimizing acoustic noise from the fan.
Each device measures two temperature locations.
The MAX6643/MAX6644/MAX6645 generate a PWM
waveform that drives an external power transistor, which
in turn modulates the fan’s power supply. The
MAX6643/MAX6644/MAX6645 monitor temperature and
adjust the duty cycle of the PWM output waveform to con-
trol the fan’s speed according to the cooling needs of the
system. The MAX6643 monitors its own die temperature
and an optional external transistor’s temperature, while the
MAX6644 and MAX6645 each monitor the temperatures
of one or two external diode-connected transistors.
The MAX6643/MAX6644/MAX6645 are available in H
and L versions. The H versions are trimmed for higher
temperature trip thresholds than the L versions. The
MAX6643 and MAX6644 have nine selectable trip tem-
peratures (in 5°C increments). The MAX6645 is factory
programmed and is not pin selectable.
All versions include an overtemperature output (OT).
OT
can be used for warning or system shutdown. The
MAX6643 also features a FULLSPD input that forces the
PWM duty cycle to 100%. The MAX6643/MAX6644/
MAX6645 also feature a
FANFAIL
output that indicates
a failed fan. See the
Selector Guide
for a complete list
of each device’s functions.
The MAX6643 and MAX6644 are available in a small
16-pin QSOP package and the MAX6645 is available in
a 10-pin µMAX
®
package. All versions operate from
3.0V to 5.5V supply voltages and consume 500µA (typ)
supply current.
Features
♦
Simple, Automatic Fan-Speed Control
♦
Internal and External Temperature Sensing
♦
Detect Fan Failure Through Locked-Rotor Output,
Tachometer Output, or Fan-Supply Current
Sensing
♦
Multiple, 1.6% Output Duty-Cycle Steps for Low
Audibility of Fan-Speed Changes
♦
Pin-Selectable or Factory-Selectable Low-
Temperature Fan Threshold
♦
Pin-Selectable or Factory-Selectable High-
Temperature Fan Threshold
♦
Spin-Up Time Ensures Fan Start
♦
Fan-Start Delay Minimizes Power-Supply Load at
Power-Up
♦
32Hz PWM Output
♦
Controlled Duty-Cycle Rate-of-Change Ensures
Good Acoustic Performance
♦
2°C Temperature-Measurement Accuracy
♦
FULLSPD/FULLSPD
Input Sets PWM to 100%
♦
Pin-Selectable
OT
Output Threshold
♦
16-Pin QSOP and 10-Pin µMAX Packages
MAX6643/MAX6644/MAX6645
Applications
Networking Equipment
Storage Equipment
Servers
Desktop Computers
Workstations
PART
MAX6643LBFAEE
MAX6643LAFAEE*
MAX6643LBBAEE
MAX6643LABAEE*
MAX6643HAFAEE*
MAX6644LBAAEE
MAX6644HAFAEE*
Ordering Information
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
16 QSOP
16 QSOP
16 QSOP
16 QSOP
16 QSOP
16 QSOP
16 QSOP
10 µMAX
10 µMAX
Pin Configurations, Typical Operating Circuit, and Selector
Guide appear at end of data sheet.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
MAX6645ABFAUB*
MAX6645BAFAUB
*Future
product—contact factory for availability.
________________________________________________________________
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.
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
MAX6643/MAX6644/MAX6645
ABSOLUTE MAXIMUM RATINGS
V
DD
to GND ..............................................................-0.3V to +6V
PWM_OUT,
OT,
and
FANFAIL
to GND.....................-0.3V to +6V
FAN_IN1 and FAN_IN2 to GND...........................-0.3V to +13.2V
DXP_ to GND.........................................................-0.3V to +0.8V
FULLSPD,
FULLSPD,
TH_, TL_, TACHSET,
and OT_ to GND ..................................-0.3V to +(V
DD
+ 0.3V)
FANFAIL, OT
Current ..........................................-1mA to +50mA
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
16-Pin QSOP (derate 8.3mW/°C above +70°C).......... 667mW
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
DD
= +3.0V to +5.5V, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
DD
= +3.3V, T
A
= +25°C.) (Note 1)
PARAMETER
Operating Supply Voltage Range
Remote Temperature Error
SYMBOL
V
DD
V
DD
= +3.3V,
+20°C
≤
T
RJ
≤
+100°C
V
CC
= +3.3V
T
A
= +20°C to +60°C
T
A
= 0°C to +125°C
T
A
= +10°C to +70°C
T
A
= 0°C to +125°C
±0.2
V
DD
falling edge
I
S
During a conversion
Duty cycle = 50%, no load
High level
MAX664_ _A_ _ _ _
MAX664_ _B_ _ _ _
MAX664_ _A_ _ _ _
MAX664_ _B_ _ _ _
80
100
125
2.5
8
2.5
0.5
16
F
PWM_OUT
V
OL
V
OL
I
OH
I
SINK
= 1mA
I
SINK
= 6mA
I
SINK
= 1mA
V
OH
= 3.3V
32
0.4
0.5
0.4
1
1.5
2.0
90
0.5
1
0.5
120
2.5
CONDITIONS
MIN
+3.0
TYP
MAX
+5.5
±2
°C
±3
±2.5
±3.5
°C
°C/V
V
mV
mA
mA
µA
ms
s
s
Hz
Hz
V
V
µA
UNITS
V
Local Temperature Error
Temperature Error from Supply
Sensitivity
Power-On-Reset (POR) Threshold
POR Threshold Hysteresis
Operating Current
Average Operating Current
Remote-Diode Sourcing Current
Conversion Time
Spin-Up Time
Startup Delay
Minimum Fan-Fail Tachometer
Frequency
PWM_OUT Frequency
Output Low Voltage (OT)
Output Low Voltage
(FANFAIL, PWM_OUT)
Output-High Leakage Current
DIGITAL OUTPUTS (OT,
FANFAIL,
PWM_OUT)
2
_______________________________________________________________________________________
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= +3.0V to +5.5V, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
DD
= +3.3V, T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
V
DD
= 5.5V
V
DD
= 3.0V
V
DD
= 3.0V
V
IN
= GND or V
DD
-1
CONDITIONS
MIN
3.65
2.2
0.8
+1
TYP
MAX
UNITS
DIGITAL INPUTS (FULLSPD, FULLSPD, TACHSET)
Logic-Input High
Logic-Input Low
Input Leakage Current
V
IH
V
IL
V
V
µA
MAX6643/MAX6644/MAX6645
Note 1:
All parameters tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
OPERATING SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6643 toc01
PWMOUT FREQUENCY
vs. DIE TEMPERATURE
MAX6643 toc02
400
32.0
320
PWMOUT FREQUENCY (Hz)
3.0
3.5
4.0
4.5
5.0
5.5
360
SUPPLY CURRENT (µA)
31.8
31.6
280
31.4
240
31.2
200
SUPPLY VOLTAGE (V)
31.0
-40
-15
10
35
60
85
100
TEMPERATURE (°C)
PWMOUT FREQUENCY
vs. SUPPLY VOLTAGE
MAX6643 toc03
TRIP-THRESHOLD ERROR
vs. TRIP TEMPERATURE
MAX664_L VERSIONS
MAX6643 toc04
35
1.0
PWMOUT FREQUENCY (Hz)
34
TRIP-THRESHOLD ERROR (°C)
0.6
33
0.2
32
-0.2
31
-0.6
30
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
-1.0
20
40
60
80
100
TRIP TEMPERATURE (°C)
_______________________________________________________________________________________
3
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
MAX6643/MAX6644/MAX6645
Pin Description
PIN
MAX6643_A MAX6643_B
1, 15
1, 15
MAX6644_
1, 15
MAX6645_
—
NAME
FUNCTION
High-Temperature Threshold Inputs. Connect to V
DD
, GND,
or leave unconnected to select the upper fan-control trip
temperature (T
HIGH
), in 5°C increments. See Table 1.
Low-Temperature Threshold Inputs. Connect to V
DD
, GND,
or leave unconnected to select the lower fan-control trip
temperature (T
LOW
), in 5°C increments. See Table 2.
Fan-Fail Alarm Output.
FANFAIL
is an active-low, open-
drain output. If the FAN_IN_ detects a fan failure, the
FANFAIL
output asserts low.
FAN_IN_ Control Input. TACHSET controls what type of fan-
fail condition is being detected. Connect TACHSET to V
DD
,
GND, or leave floating to set locked rotor, current sense, or
tachometer configurations (see Table 3).
Active-High Logic Input. When pulled high, the fan runs at
100% duty cycle.
Active-Low Logic Input. When pulled low, the fan runs at
100% duty cycle.
Ground
TH1, TH2
2, 3
2, 3
2, 3
—
TL2, TL1
4
4
4
1
FANFAIL
5
5
5
2
TACHSET
—
6
7
8
6
—
7
8
—
—
7
—
—
—
4
—
FULLSPD
FULLSPD
GND
DXP
—
9
—
9
6, 8
9
3, 5
6
Combined Current Source and A/D Positive Input for Remote
Diode. Connect to anode of remote diode-connected
temperature-sensing transistor. Connect to GND if no remote
diode is used. Place a 2200pF capacitor between DXP_ and
DXP2, DXP1
GND for noise filtering.
OT
Active-Low, Open-Drain Overtemperature Output. When
OT
threshold is exceeded,
OT
pulls low.
Fan-Sense Input. FAN_IN_ can be configured to monitor either
a fan’s logic-level locked-rotor output, tachometer output, or
sense-resistor waveform to detect fan failure. The MAX6643’s
FAN_IN_ input can monitor only tachometer signals. The
MAX6644 and the MAX6645 can monitor any one of the three
signal types as configured using the TACHSET input.
10, 11
10, 11
10, 11
7, 8
FAN_IN2,
FAN_IN1
4
_______________________________________________________________________________________
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
Pin Description (continued)
PIN
MAX6643_A MAX6643_B
MAX6644_
MAX6645_
NAME
FUNCTION
PWM Output for Driving External Power Transistor. Connect
to the gate of an n-channel MOSFET or to the base of an
npn. PWMOUT requires a pullup resistor. The pullup
resistor can be connected to a supply voltage as high as
5.5V, regardless of the supply voltage.
Overtemperature Threshold Inputs. Connect to V
DD
, GND,
or leave unconnected to select the upper-limit
OT
fault
output trip temperature, in 5°C increments. See Table 4.
Power-Supply Input. 3.3V nominal. Bypass V
DD
to GND with
a 0.1µF capacitor.
MAX6643/MAX6644/MAX6645
12
12
12
9
PWM_OUT
13, 14
13, 14
13, 14
—
OT2, OT1
16
16
16
10
V
DD
Detailed Description
The MAX6643/MAX6644/MAX6645 measure temperature
and automatically adjust fan speed to ensure optimum
cooling while minimizing acoustic noise from the fan.
The MAX6643/MAX6644/MAX6645 generate a PWM
waveform that drives an external power transistor,
which in turn modulates the fan’s power supply. The
MAX6643/MAX6644/MAX6645 monitor temperature and
adjust the duty cycle of the PWM output waveform to
control the fan’s speed according to the cooling needs
of the system. The MAX6643 monitors its own die tem-
perature and an optional external transistor’s tempera-
ture, while the MAX6644 and MAX6645 each monitor
the temperatures of one or two external diode-connect-
ed transistors.
the low-temperature threshold (T
LOW
), and the overtem-
perature threshold,
OT.
The
OT
comparison is done once
per second, whereas the comparisons with fan-control
thresholds T
HIGH
and T
LOW
are done once every 4s.
The duty-cycle variation of PWM_OUT from 0% to 100%
is divided into 64 steps. If the temperature measured
exceeds the threshold T
HIGH
, the PWM_OUT duty cycle
is incremented by one step, i.e., approximately 1.5%
(100/64). Similarly, if the temperature measured is below
the threshold T
LOW
, the duty cycle is decremented by
one step (1.5%). Since the T
HIGH
and T
LOW
compar-
isons are done only once every 4s, the maximum rate of
change of duty cycle is 0.4% per second.
Tables 1 and 2 show the °C value assigned to the TH_
and TL_ input combinations.
Temperature Sensor
The pn junction-based temperature sensor can mea-
sure temperatures up to two pn junctions. The
MAX6643 measures the temperature of an external
diode-connected transistor, as well as its internal tem-
perature. The MAX6644 and MAX6645 measure the
temperature of two external diode-connected transis-
tors. The temperature is measured at a rate of 1Hz.
If an external “diode” pin is shorted to ground or left
unconnected, the temperature is read as 0°C. Since the
larger of the two temperatures prevails, a faulty or
unconnected diode is not used for calculating fan
speed or determining overtemperature faults.
Table 1. Setting T
HIGH
(MAX6643 and MAX6644)
TH2
0
0
0
High-Z
High-Z
High-Z
1
1
1
TH1
0
High-Z
1
0
High-Z
1
0
High-Z
1
T
HIGH
(°C)
L SUFFIX
20
25
30
35
40
45
50
55
60
T
HIGH
(°C)
H SUFFIX
40
45
50
55
60
65
70
75
80
PWM Output
The larger of the two measured temperatures is always
used for fan control. The temperature is compared to
three thresholds: the high-temperature threshold (T
HIGH
),
High-Z = High impedance.
_______________________________________________________________________________________
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