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PDF MAX6644 Data sheet ( Hoja de datos )
| Número de pieza | MAX6644 | |
| Descripción | Automatic PWM Fan-Speed Controllers | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-3305; Rev 0; 5/04
Automatic PWM Fan-Speed Controllerswwww.DatiatShheet4U.com
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
supply voltages from 3.0V to 5.5V and consume 500µA
(typ) supply current.
Applications
Networking Equipment
Storage Equipment
Servers
Desktop Computers
Workstations
Pin Configurations, Typical Operating Circuit, and Selector
Guide appear at end of data sheet.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
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
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX6643LBFAEE
-40°C to +125°C 16 QSOP
MAX6643LAFAEE*
-40°C to +125°C 16 QSOP
MAX6643LBBAEE* -40°C to +125°C 16 QSOP
MAX6643LABAEE* -40°C to +125°C 16 QSOP
MAX6643HAFAEE* -40°C to +125°C 16 QSOP
MAX6644LAAAEE* -40°C to +125°C 16 QSOP
MAX6644HAFAEE* -40°C to +125°C 16 QSOP
MAX6645AAFAUB* -40°C to +125°C 10 µMAX
MAX6645BAFAUB* -40°C to +125°C 10 µMAX
*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.
1 page  
Automatic PWM Fan-Speed Controllerswwww.DatiatShheet4U.com
Overtemperature Output
Pin Description (continued)
PIN
MAX6643_A MAX6643_B MAX6644_
12 12 12
MAX6645_
9
NAME
PWM_OUT
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.
13, 14
13, 14
13, 14
Overtemperature Threshold Inputs. Connect to VDD, GND,
— OT1, OT2 or leave unconnected to select the upper-limit OT fault
output trip temperature, in 5°C increments. See Table 4.
16
16
16
10
VDD
Power-Supply Input. 3.3V nominal. Bypass VDD to GND with
a 0.1µF capacitor.
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 (THIGH),
the low-temperature threshold (TLOW), and the overtem-
perature threshold, OT. The OT comparison is done once
per second, whereas the comparisons with fan-control
thresholds THIGH and TLOW 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 THIGH, 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 TLOW, the duty cycle is decremented by
one step (1.5%). Since the THIGH and TLOW 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 shows the °C value assigned to the TH_
and TL_ input combinations.
Table 1. Setting THIGH
(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
THIGH (°C)
L SUFFIX
20
25
30
35
40
45
50
55
60
THIGH (°C)
H SUFFIX
40
45
50
55
60
65
70
75
80
_______________________________________________________________________________________ 5
5 Page 
Automatic PWM Fan-Speed Controllerswwww.DatiatShheet4U.com
Overtemperature Output
4.7kΩ
TO FANFAIL
ALARM
4.7kΩ
TO FANFAIL
ALARM
VDD (+3.0V TO +5.5V)
+VFAN (5V OR 12V)
1
TH1
2
TL2
3
TL1
MAX6643_A_
16
VDD
15
TH2
14
OT1
4 FANFAIL
13
OT2
4.7kΩ 4.7kΩ
5 TACHSET
12
PWM_OUT
6 FULLSPD
11 (TACHOMETER MODE)
FAN_IN1
7 GND
10 (TACHOMETER MODE)
FAN_IN2
8 DXP
OT 9
VDD (+3.0V TO +5.5V)
N
TO OVERTEMPERATURE ALARM
+VFAN (5V OR 12V)
1
TH1
2
TL2
16
VDD
15
TH2
3 TL1
MAX6643_A_
14
OT1
4 FANFAIL
13
OT2
4.7kΩ 4.7kΩ
5 TACHSET
12
PWM_OUT
6 FULLSPD
FAN_IN1 11 (TACHOMETER MODE)
7 GND
FAN_IN2 10 (TACHOMETER MODE)
8 DXP
OT 9
N
TO OVERTEMPERATURE ALARM
Figure 6. Using Two MAX6643s, Each Controlling a Separate Fan
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet MAX6644.PDF ] | |
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