OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

MAX6644LBAAEE+T

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P17
MAX6643/MAX6644/MAX6645
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
4 _______________________________________________________________________________________
Pin Description
PIN
MAX6643 MAX6644 MAX6645
NAME FUNCTION
1, 15 1, 15 — TH1, TH2
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.
2, 3 2, 3 — TL2, TL1
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.
441FANFAIL
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.
5 5 2 TACHSET
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).
6 — — FULLSPD
Active-High Logic Input. When pulled high, the fan runs at
100% duty cycle.
———FULLSPD
Active-Low Logic Input. When pulled low, the fan runs at 100%
duty cycle.
7 7 4 GND Ground
8 — — DXP
— 6, 8 3, 5 DXP2, DXP1
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 .
996OT
Active-Low, Open-Drain Overtemperature Output. When OT
threshold is exceeded, OT pulls low.
10, 11 10, 11 7, 8
FAN_IN2,
FAN_IN1
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 sense-
r 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.
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.
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.
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
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.
MAX6643/MAX6644/MAX6645
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
_______________________________________________________________________________________ 5
Pin Description (continued)
PIN
MAX6643 MAX6644 MAX6645
NAME FUNCTION
12 12 9 PWM_OUT
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.
13, 14 13, 14 — OT2, OT1
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.
16 16 10 V
DD
Power-Supply Input. 3.3V nominal. Bypass V
DD
to GND with a
0.1µF capacitor.
TH2 TH1
T
HIGH
(°C)
L SUFFIX
T
HIGH
(°C)
H SUFFIX
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
Table 1. Setting T
HIGH
(MAX6643 and MAX6644)
High-Z = High impedance.
MAX6643/MAX6644/MAX6645
There are two options for the behavior of the PWM out-
puts 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 power-
up, 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 temper-
ature 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 temper-
ature 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, incre-
menting 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)
STARTUP
DUTY CYCLETEMPERATURE
TIME
TIME
T
HIGH
SPIN-UP
T
LOW
Figure 1. Temperature-Controlled Duty-Cycle Change with
Minimum Duty Cycle 30%
STARTUP
MAX664_B HAS 30% PWM_OUT DUTY CYCLE DURING STARTUP.
DUTY CYCLETEMPERATURE
TIME
TIME
T
HIGH
T
LOW
SPIN-UP
Figure 2. Temperature-Controlled Duty-Cycle Change with
Minimum Duty Cycle 30%
TL2 TL1
T
LOW
(°C)
L SUFFIX
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
High-Z = High impedance.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P17

MAX6644LBAAEE+T

Mfr. #:
Buy MAX6644LBAAEE+T
Manufacturer:
Maxim Integrated
Description:
Motor / Motion / Ignition Controllers & Drivers Automatic PWM Fan Speed Controller
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet