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 control 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 and MAX6644 have nine selectable trip
temperatures (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.
Applications
Networking Equipment
Storage Equipment
Servers
Desktop Computers
Workstations
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
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-3305; Rev 2; 3/07
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.
EVALUATION KIT
AVAILABLE
Pin Configurations, Typical Operating Circuit, and Selector
Guide appear at end of data sheet.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
PART TEMP RANGE
MAX6643LBFAEE -40°C to +125°C 16 QSOP E16-1
MAX6643LBBAEE -40°C to +125°C 16 QSOP E16-1
MAX6644LBAAEE -40°C to +125°C 16 QSOP E16-1
MAX6645ABFAUB -40°C to +125°C 10 µMAX U10-2
PINPACKAGE
PKG
CODE
MAX6643/MAX6644/MAX6645
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VDD= +3.0V to +5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VDD= +3.3V, TA= +25°C.) (Note 1)
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.
VDDto 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)
16-Pin QSOP (derate 8.3mW/°C above +70°C).......... 667mW
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
Operating Supply Voltage Range V
Remote Temperature Error
Local Temperature Error VCC = +3.3V
Temperature Error from Supply
Sensitivity
Power-On-Reset (POR) Threshold VDD falling edge 1.5 2.0 2.5 V
POR Threshold Hysteresis 90 mV
Operating Current I
Average Operating Current Duty cycle = 50%, no load 0.5 mA
Remote-Diode Sourcing Current High level 80 100 120 µA
Conversion Time 125 ms
Spin-Up Time MAX664_ _B_ _ _ _ 8 s
Startup Delay MAX664_ _B_ _ _ _ 0.5 s
Minimum Fan-Fail Tachometer
Frequency
PWM_OUT Frequency F
DIGITAL OUTPUTS (OT, FANFAIL, PWM_OUT)
Output Low Voltage (OT)V
Output Low Voltage
(FANFAIL, PWM_OUT)
Output-High Leakage Current I
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DD
= +3.3V,
S
PWM_OUT
OL
V
OL
OH
V
DD
+20°C ≤ T
+100°C
During a conversion 0.5 1 mA
I
SINK
I
SINK
I
SINK
VOH = 3.3V 1 µA
RJ
= 1mA 0.4 V
= 6mA 0.5
= 1mA 0.4
TA = +20°C to +60°C ±2
≤
= 0°C to +125°C ±3
T
A
TA = +10°C to +70°C ±2.5
T
= 0°C to +125°C ±3.5
A
+3.0 +5.5 V
±0.2 °C/V
16 Hz
32 Hz
°C
°C
V
MAX6643/MAX6644/MAX6645
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
_______________________________________________________________________________________ 3
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
ELECTRICAL CHARACTERISTICS (continued)
(VDD= +3.0V to +5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VDD= +3.3V, TA= +25°C.) (Note 1)
Note 1: All parameters tested at TA= +25°C. Specifications over temperature are guaranteed by design.
DIGITAL INPUTS (FULLSPD, FULLSPD, TACHSET)
Logic-Input High V
Logic-Input Low V
Input Leakage Current VIN = GND or V
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VDD = 5.5V 3.65
IH
VDD = 3.0V 2.2
VDD = 3.0V 0.8 V
IL
DD
-1 +1 µA
OPERATING SUPPLY CURRENT
vs. SUPPLY VOLTAGE
400
360
MAX6643 toc01
32.0
31.8
PWMOUT FREQUENCY
vs. DIE TEMPERATURE
MAX6643 toc02
V
320
280
SUPPLY CURRENT (μA)
240
200
3.0 5.5
SUPPLY VOLTAGE (V)
PWMOUT FREQUENCY
vs. SUPPLY VOLTAGE
35
34
33
32
PWMOUT FREQUENCY (Hz)
31
30
3.0 5.5
SUPPLY VOLTAGE (V)
31.6
31.4
PWMOUT FREQUENCY (Hz)
31.2
5.04.54.03.5
31.0
-40
10085603510-15
TEMPERATURE (°C)
TRIP-THRESHOLD ERROR
vs. TRIP TEMPERATURE
1.0
MAX664_L VERSIONS
MAX6643 toc03
5.04.54.03.5
0.6
0.2
-0.2
TRIP-THRESHOLD ERROR (°C)
-0.6
-1.0
20 100
TRIP TEMPERATURE (°C)
806040
MAX6643 toc04
MAX6643/MAX6644/MAX6645
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
4 _______________________________________________________________________________________
Pin Description
PIN
MAX6643 MAX6644 MAX6645
1, 15 1, 15 — TH1, TH2
NAME FUNCTION
High-Temperature Threshold Inputs. Connect to V
leave unconnected to select the upper fan-control trip
temperature (T
), in 5°C increments. See Table 1.
HIGH
DD
, GND, or
Low-Temperature Threshold Inputs. Connect to V
2, 3 2, 3 — TL2, TL1
441FANFAIL
5 5 2 TACHSET
6 — — FULLSPD
———FULLSPD
7 7 4 GND Ground
8 — — DXP
— 6, 8 3, 5 DXP2, DXP1
996OT
10, 11 10, 11 7, 8
FAN_IN2,
FAN_IN1
leave unconnected to select the lower fan-control trip
temperature (T
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
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.
C om b i ned C ur r ent S our ce and A/D P osi ti ve Inp ut for Rem ote
D i od e. C onnect to anod e of r em ote d i od e- connected
tem p er atur e- sensi ng tr ansi stor . C onnect to G N D i f no r em ote
d i od e i s used . P l ace a 2200p F cap aci tor b etw een D X P _ and
G N D for noi se fi l ter i ng .
Active-Low, Open-Drain Overtemperature Output. When OT
threshold is exceeded, OT pulls low.
Fan- S ense Inp ut. FAN _IN _ can b e confi g ur ed to m oni tor ei ther a
fan’ s l og i c- l evel l ocked - r otor outp ut, tachom eter outp ut, or senser esi stor w avefor m to d etect fan fai l ur e. The M AX 6643’ s FAN _IN _
i np ut can m oni tor onl y tachom eter si g nal s. The M AX 6644 and the
M AX 6645 can m oni tor any one of the thr ee si g nal typ es as
confi g ur ed usi ng the TAC H S E T i np ut.
), in 5°C increments. See Table 2.
LOW
, GND, or
DD
DD
, GND,
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 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.
Temperature Sensor
The pn junction-based temperature sensor can measure temperatures up to two pn junctions. The
MAX6643 measures the temperature of an external
diode-connected transistor, as well as its internal temperature. The MAX6644 and MAX6645 measure the
temperature of two external diode-connected transistors. 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.
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
),
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
comparisons 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.
MAX6643/MAX6644/MAX6645
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
_______________________________________________________________________________________ 5
Pin Description (continued)
Table 1. Setting T
HIGH
(MAX6643 and MAX6644)
High-Z = High impedance.
PIN
MAX6643 MAX6644 MAX6645
12 12 9 PWM_OUT
13, 14 13, 14 — OT2, OT1
16 16 10 V
NAME FUNCTION
DD
PWM Output for Driving External Power Transistor. Connect to
the gate of an n-channel MOSFET or to the base of an npn.
PWM_OUT 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
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 VDD to GND with a
0.1µF capacitor.
, GND, or
DD
TH2 TH1
0 0 20 40
0 High-Z 25 45
0 1 30 50
High-Z 0 35 55
High-Z High-Z 40 60
High-Z 1 45 65
1 0 50 70
1 High-Z 55 75
1 1 60 80
T
HIGH
L SUFFIX
(°C)
T
(°C)
HIGH
H SUFFIX
MAX6643/MAX6644/MAX6645
There are two options for the behavior of the PWM outputs at power-up. Option 1 (minimum duty cycle = 0):
at power-up, the PWM duty cycle is zero. Option 2
(minimum duty cycle = the start duty cycle): at powerup, there is a startup delay, after which the duty cycle
goes to 100% for the spin-up period. After the startup
delay and spin-up, the duty cycle drops to its minimum
value. The minimum duty cycle is in the 0% to 50%
range (see the Selector Guide).
To control fan speed based on temperature, T
HIGH
is
set to the temperature beyond which the fan should spin
at 100%. T
LOW
is set to the temperature below which
the duty cycle can be reduced to its minimum value.
After power-up and spin-up (if applicable), the duty
cycle reduces to its minimum value (either 0% or the
start duty cycle). For option 1 (minimum duty cycle = 0),
if the measured temperature remains below T
HIGH
, the
duty cycle remains at zero (see Figure 1). If the temperature increases above T
HIGH
, the duty cycle goes to
100% for the spin-up period, and then goes to the start
duty cycle (for example, 40%). If the measured temperature remains above T
HIGH
when temperature is next
measured (4s later), the duty cycle begins to increase,
incrementing by 1.5% every 4s until the fan is spinning
fast enough to reduce the temperature below T
HIGH
.
For option 2 (minimum duty cycle = start duty cycle), if
the measured temperature remains below T
HIGH
, the
duty cycle does not increase and the fan continues to
run at a slow speed. If the temperature increases
above T
HIGH
, the duty cycle begins to increase, incrementing by 1.5% every 4s until the fan is spinning fast
enough to reduce the temperature below T
HIGH
(see
Figure 2). In both cases, if only a small amount of extra
cooling is necessary to reduce the temperature below
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
6 _______________________________________________________________________________________
Table 2. Setting T
LOW
(MAX6643 and MAX6644)
Figure 1. Temperature-Controlled Duty-Cycle Change with
Minimum Duty Cycle 30%
Figure 2. Temperature-Controlled Duty-Cycle Change with
Minimum Duty Cycle 30%
(°C)
T
TL2 TL1
0015
0 High-Z 20
0125
High-Z 0 30
High-Z High-Z 35
High-Z 1 40
1045
1 High-Z 50
1155
LOW
L SUFFIX
DUTY CYCLETEMPERATURE
DUTY CYCLETEMPERATURE
SPIN-UP
STARTUP
SPIN-UP
STARTUP
MAX664_B HAS 30% PWM_OUT DUTY CYCLE DURING STARTUP.
TIME
TIME
TIME
TIME
T
HIGH
T
LOW
T
HIGH
T
LOW