Maxim MAX6665 Fan controller/driver with factory- programmed temperature threshold Datasheet

19-2056; Rev 0; 5/01
Fan Controller/Driver with FactoryProgrammed Temperature Thresholds
Applications
Notebook and Desktop Computers
Features
♦ On-Chip 250mA Fan Switch
♦ No External Components Required
♦ Factory-Programmed Thresholds
♦ Two Overtemperature Warning Signals
♦ Pin-Selectable 1°C, 4°C, and 8°C Hysteresis
♦ Low 65µA Supply Current
Ordering Information
PART
TEMP.
RANGE
PINPACKAGE
MAX6665ASA40
-40°C to
+125°C
8 SO-EP*
40°C
MAX6665ASA45
-40°C to
+125°C
8 SO-EP*
45°C
MAX6665ASA50
-40°C to
+125°C
8 SO-EP*
50°C
MAX6665ASA55
-40°C to
+125°C
8 SO-EP*
55°C
MAX6665ASA60
-40°C to
+125°C
8 SO-EP*
60°C
MAX6665ASA65
-40°C to
+125°C
8 SO-EP*
65°C
MAX6665ASA70
-40°C to
+125°C
8 SO-EP*
70°C
Servers
PC Power Supplies
Laboratory Instruments
Card Racks
Typical Operating Circuit
+4.5V TO +24V
THRESHOLD
*Exposed paddle
100mA TO 250mA
COOLING FAN
Pin Configuration
TOP VIEW
VDD
+3.3V
FANOUT
VDD
1µF
MAX6665
100kΩ
GND
WARN
HYST
VDD
1
8
FANOUT
7
VDD
3
6
WARN
FANON 4
5
OT
FORCEON 2
MAX6665
100kΩ
OT
FORCEON
GND
HYST
FANON
SO
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
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1
MAX6665
General Description
The MAX6665 is a fully integrated thermal switch with
an internal power transistor for driving a cooling fan
rated up to 24V and 250mA. When the MAX6665’s temperature rises above a factory-programmed threshold,
the FANOUT pin becomes active and powers the fan.
The MAX6665 is available with factory-programmed fan
activation threshold temperatures from +40°C to +70°C
in 5°C increments. Accuracy of the fan activation trip
point is ±1°C (typ) and ±3°C (max). The trip point’s hysteresis is pin selectable to 1°C, 4°C, or 8°C. Two opendrain logic outputs indicate overtemperature conditions: WARN is activated when the temperature is
15°C above the fan activation threshold, and OT is activated when the temperature is 30°C above the threshold. These features can be used to safely power down
systems that are overheated.
The MAX6665 operates from a +2.7V to +5.5V power
supply, and the associated fan can be powered from
4.5V to 24V. It is available in an 8-pin SO package and
operates from -40°C to +125°C.
MAX6665
Fan Controller/Driver with FactoryProgrammed Temperature Thresholds
ABSOLUTE MAXIMUM RATINGS
VDD to GND ..............................................................-0.3V to +6V
FANOUT to GND ....................................................-0.3V to +28V
FORCEON, HYST, FANON to GND............-0.3V to (VDD + 0.3V)
WARN, OT to GND ...................................................-0.3V to +6V
FANOUT Continuous Current............................................400mA
All Other Pins ....................................................................±20mA
Continuous Power Dissipation (TA = +70°C)
8-Pin SO (derate 19.6mW/°C above +70°C).............1568mW
Operating Temperature Range .........................-40°C to +125°C
Junction (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
(VDD = +2.7V to +5.5V, TA = -40°C to +125°C. Typical values are at VDD = +3.3V and TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER
CONDITIONS
Supply Voltage
VDD pin
Supply Current
No load
FANOUT Drive Voltage
FANOUT pin
FANOUT Output Current Capability
FANOUT Leakage Current
FANOUT Threshold, TTH
MIN
MAX
5.5
V
65
200
µA
26
V
2.7
V FANOUT < 0.8V
250
V FANOUT < 0.6V, TA ≤ TTH +10°C, VCC ≥ +3.3V
250
3
MAX6665ASA40
40
MAX6665ASA45
45
MAX6665ASA50
50
MAX6665ASA55
55
MAX6665ASA60
60
MAX6665ASA65
65
MAX6665ASA70
UNITS
mA
V FANOUT = 26V, TA = +60°C
FANOUT Threshold Error
FANOUT Hysteresis
TYP
µA
°C
70
-3
±1
HYST is unconnected
1
HYST ≤ 0.3VDD
4
HYST ≥ 0.7VDD
8
+3
°C
°C
WARN Threshold
Relative to FANOUT temperature threshold
+15
°C
OT Threshold
Relative to FANOUT temperature threshold
+30
°C
2
°C
WARN and OT Hysteresis
FANON Output High Voltage
IFANON = 0.5mA source
FANON Output Low Voltage
IFANON = 0.5mA sink
WARN and OT Output Voltage Low
2.0
V
0.7
I WARN = 1.2mA or I OT = 1.2mA sink
0.3
I WARN = 20mA or I OT = 20mA sink
0.5
Open-Drain Leakage Current
V WARN = 5.5V or V OT = 5.5V
0.1
Input Low Voltage
FORCEON and HYST pins
Input High Voltage
FORCEON and HYST pins
Input Current
V
V
µA
0.3VDD
0.7VDD
V
V
FORCEON connected to VDD or GND
-1
+1
HYST connected to VDD or GND
-15
+15
µA
Note 1: Specifications over temperature are guaranteed by design. Parts are 100% production tested at 10°C below the temperature threshold.
2
_______________________________________________________________________________________
Fan Controller/Driver with FactoryProgrammed Temperature Thresholds
FANOUT VOLTAGE vs. CURRENT
TA = +75°C
800
VDD = +2.7V
FANOUT VOLTAGE (mV)
600
VDD = +3.3V
500
400
300
TA = +75°C
450
TA = +50°C
400
350
200
300
VDD = +5.0V
100
0
250
2.7
1000
3.1
3.5
3.9
4.3
4.7
5.1
FANOUT CURRENT (mA)
SUPPLY VOLTAGE (V)
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
TEMPERATURE THRESHOLD
DISTRIBUTION
FORCEON = VDD
80
MAX6665 toc03
90
100
VDD = +5V
VDD = +3.3V
70
60
VDD = +2.7V
50
40
50
45
5.5
MAX6665ASA55
100 SAMPLES
40
MAX6665 toc04
10
SUPPLY CURRENT (µA)
FANOUT CURRENT = 250mA
500
PERCENTAGE OF SAMPLES (%)
FANOUT VOLTAGE (mV)
700
MAX6665 toc02
FANOUT VOLTAGE vs. SUPPLY VOLTAGE
550
MAX6665 toc01
900
35
30
25
20
15
10
5
30
0
-40 -20
0
20
40
60
80 100 120
TEMPERATURE (°C)
0
-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.5 1.0 1.5 2.0 2.5 3.0
TEMPERATURE ERROR (°C)
_______________________________________________________________________________________
3
MAX6665
Typical Operating Characteristics
(VDD = +3.3V, unless otherwise noted.)
Fan Controller/Driver with FactoryProgrammed Temperature Thresholds
MAX6665
Pin Description
PIN
NAME
FUNCTION
1
GND
2
FORCEON
3
HYST
4
FANON
Fan-On Indicator Output. Push-pull output. FANON is high when the fan switch is on. FANON is low
when the fan switch is off.
5
OT
Overtemperature Output. Active-low when the temperature is 30°C above the fan threshold. Opendrain output, requires resistive pullup.
6
WARN
7
VDD
8
FANOUT
Exposed
Paddle
GND
Ground
Force Fan On Input. Set FORCEON low to force the fan switch on. Set FORCEON high for normal
operation.
Three-State Hysteresis Input. Connect HYST to VDD for 8°C, GND for 4°C, and leave HYST
unconnected for 1°C hysteresis.
Overtemperature Warning Output. Active-low when the temperature is 15°C above the fan
threshold. Open-drain output, requires resistive pullup.
Supply Voltage. Bypass with a 1µF capacitor to GND as close to VDD pin as possible.
Fan-Switch (Driver) Output. Connect to the low side of a fan.
Ground
Detailed Description
The MAX6665 is a simple fan controller/driver that turns
on the internal power transistor when its die temperature exceeds a factory-set threshold. By connecting a
small (typically 5V to 12V, 100mA to 250mA) cooling
fan to FANOUT, a simple on/off fan-control system is
created. FANOUT drives the fan’s low side. The fan’s
positive supply pin should be connected to its normal
power-supply voltage (up to 24V nominal).
To turn the fan on when the MAX6665’s die temperature
is less than the threshold voltage, drive FORCEON low.
This overrides the internal control circuitry and allows
an external device to activate the fan. FANON is an
active-high push-pull logic output that goes high when
the fan is turned on, either when temperature exceeds
the threshold or the fan is forced on.
WARN is an active-low, open-drain digital output that
indicates the MAX6665’s die temperature exceeds
15°C above the fan trip threshold. WARN output serves
as a warning that the system temperature has continued to rise well above the fan activation temperature.
OT is an active-low open-drain digital output that indicates the MAX6665’s die temperature exceeds 30°C
above the fan trip threshold. It serves as a thermal shutdown output to the system in case of excessive temperature rise. Figure 1 shows a typical application circuit
for a high-reliability, fail-safe temperature monitor.
4
Applications Information
Thermal Considerations and Hysteresis
The temperature comparator has hysteresis to prevent
small temperature changes near the threshold temperature from causing the fan to turn on and off repeatedly
over short periods of time. The FANOUT pin goes
active and powers the fan when the MAX6665’s die
temperature exceeds the factory-programmed trip temperature. As the cooling fan operates, the circuit board
temperature should decrease, which in turn causes the
MAX6665’s die temperature to decrease. When the die
temperature is equal to the trip threshold minus the
hysteresis, the FANOUT pin turns the fan off, removing
power from the fan. The HYST pin sets the amount of
hysteresis to 1°C, 4°C, or 8°C by letting the pin float or
connecting to GND or VDD, respectively. This allows
the amount of hysteresis to be matched to the cooling
and noise requirements of the system.
Hysteresis is also affected by self-heating of the
MAX6665’s die. The fan current flowing through the onchip power transistor causes the die temperature to
increase. For example, assume the MAX6665 controls
a 125mA fan. When the fan is operating, the voltage
drop across the output transistor is typically under
250mV. At 250mV, the power dissipation is 31.25mW.
The thermal resistance of the MAX6665 package (with
EP soldered) is 51°C/W, so the die temperature
_______________________________________________________________________________________
Fan Controller/Driver with FactoryProgrammed Temperature Thresholds
MAX6665
+4.5V TO +24V
100mA TO 250mA
COOLING FAN
VDD
+3.3V
FANOUT
VDD
1µF
MAX6665
100kΩ
HYST
WARN
FORCEON
FANON
I/O
µP
I/O
VDD
100kΩ
SYSTEM POWER
SHUTDOWN
OT
GND
Figure 1. High-Reliability, Fail-Safe Fan Controller and Temperature Monitor
increases by a maximum of:
51°C/W x 0.03125W = 1.59°C
Therefore, the effective hysteresis is about 1.59°C higher than the hysteresis selected by the HYST pin. For
example, setting the HYST pin for 8°C of hysteresis
results in an effective hysteresis of about 9.6°C.
A larger fan with a power-supply current of 250mA
causes a maximum voltage drop of 0.6V at the output
pin. This results in 150mW power dissipation and the
die temperature increases by:
51°C/W x 0.150W = 7.65°C
If the HYST pin has been set for 8°C of hysteresis, the
total effective hysteresis will be about 15.7°C.
Using fans with somewhat higher operating current
than 250mA results in higher voltage across the output
transistor. The increased power dissipation caused by
the higher current and voltage levels will increase selfheating, thereby increasing the effective hysteresis.
When using higher-power fans, be sure that the
MAX6665’s power dissipation does not cause so much
self-heating that the MAX6665 stays on constantly.
Locating the MAX6665
The location of the MAX6665 in the system affects its
operation. Because the fan is turned on and off based
on the MAX6665’s die temperature, place the MAX6665
close to major heat-generating components in the system—a high-speed CPU or a power device, for example. A higher supply voltage reduces the FANOUT
voltage, which reduces the self-heating effects.
The die temperature of the MAX6665 tracks the temperature of its leads and the EP. If it is soldered to a PC board,
it quickly reaches the temperature of the traces in that
section of the circuit board. Air temperature affects the die
temperature. Since the plastic package does not conduct
heat as well as the leads, the effect of air temperature is
much less than that of lead temperature.
Layout Issues
The MAX6665’s GND pin is ground return for the fan driver and the device. Large fan current induces noise
(ground bounce) to the MAX6665. Bypass VDD to GND
with a 1µF tantalum capacitor located as close to the
MAX6665 as possible. For long VDD and GND lines, an
additional bypass capacitor may be needed. The bypass
capacitor reduces GND noise. The EP is internally connected to the GND pin. Solder the EP to the ground plane
for better electrical and thermal performance.
_______________________________________________________________________________________
5
Chip Information
TRANSISTOR COUNT: 1543 MOS
119 BIPOLAR
PROCESS: BiCMOS
Package Information
8L, SOIC EXP. PAD.EPS
MAX6665
Fan Controller/Driver with FactoryProgrammed Temperature Thresholds
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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