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19-2056; Rev 0; 5/01
Fan Controller/Driver with FactoryProgrammed Temperature Thresholds
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 +40C to +70C in 5C increments. Accuracy of the fan activation trip point is 1C (typ) and 3C (max). The trip point's hysteresis is pin selectable to 1C, 4C, or 8C. Two opendrain logic outputs indicate overtemperature conditions: WARN is activated when the temperature is 15C above the fan activation threshold, and OT is activated when the temperature is 30C 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 -40C to +125C. o On-Chip 250mA Fan Switch o No External Components Required o Factory-Programmed Thresholds o Two Overtemperature Warning Signals o Pin-Selectable 1C, 4C, and 8C Hysteresis o Low 65A Supply Current
Features
MAX6665
Ordering Information
PART MAX6665ASA40 MAX6665ASA45 MAX6665ASA50 MAX6665ASA55 MAX6665ASA60 MAX6665ASA65 MAX6665ASA70 TEMP. RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C PINPACKAGE 8 SO-EP* 8 SO-EP* 8 SO-EP* 8 SO-EP* 8 SO-EP* 8 SO-EP* 8 SO-EP* THRESHOLD 40C 45C 50C 55C 60C 65C 70C
Applications
Notebook and Desktop Computers Servers PC Power Supplies Laboratory Instruments Card Racks
Typical Operating Circuit
+4.5V TO +24V 100mA TO 250mA COOLING FAN
*Exposed paddle
Pin Configuration
TOP VIEW
+3.3V 1F
VDD
FANOUT
VDD 100k
MAX6665
HYST WARN
GND VDD 100k
1
8 7
FANOUT VDD WARN OT
FORCEON 2
MAX6665
HYST 3 6 5 FORCEON GND OT FANON FANON 4
SO
________________________________________________________________ Maxim Integrated Products
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Fan Controller/Driver with FactoryProgrammed Temperature Thresholds MAX6665
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 = +70C) 8-Pin SO (derate 19.6mW/C above +70C).............1568mW Operating Temperature Range .........................-40C to +125C Junction (storage) Temperature Range ............-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 = -40C to +125C. Typical values are at VDD = +3.3V and TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Supply Voltage Supply Current FANOUT Drive Voltage FANOUT Output Current Capability FANOUT Leakage Current VDD pin No load FANOUT pin V FANOUT < 0.8V V FANOUT < 0.6V, TA TTH +10C, VCC +3.3V V FANOUT = 26V, TA = +60C MAX6665ASA40 MAX6665ASA45 MAX6665ASA50 FANOUT Threshold, TTH MAX6665ASA55 MAX6665ASA60 MAX6665ASA65 MAX6665ASA70 FANOUT Threshold Error HYST is unconnected FANOUT Hysteresis WARN Threshold OT Threshold WARN and OT Hysteresis FANON Output High Voltage FANON Output Low Voltage WARN and OT Output Voltage Low Open-Drain Leakage Current Input Low Voltage Input High Voltage Input Current IFANON = 0.5mA source IFANON = 0.5mA sink I WARN = 1.2mA or I OT = 1.2mA sink I WARN = 20mA or I OT = 20mA sink V WARN = 5.5V or V OT = 5.5V FORCEON and HYST pins FORCEON and HYST pins FORCEON connected to VDD or GND HYST connected to VDD or GND 0.7VDD -1 -15 +1 +15 0.5 0.1 0.3VDD 2.0 0.7 0.3 HYST 0.3VDD HYST 0.7VDD Relative to FANOUT temperature threshold Relative to FANOUT temperature threshold -3 250 250 3 40 45 50 55 60 65 70 1 1 4 8 +15 +30 2 C C C V V V A V V A C +3 C C CONDITIONS MIN 2.7 65 TYP MAX 5.5 200 26 UNITS V A V mA A
Note 1: Specifications over temperature are guaranteed by design. Parts are 100% production tested at 10C below the temperature threshold. 2 _______________________________________________________________________________________
Fan Controller/Driver with FactoryProgrammed Temperature Thresholds MAX6665
Typical Operating Characteristics
(VDD = +3.3V, unless otherwise noted.)
FANOUT VOLTAGE vs. CURRENT
MAX6665 toc01
FANOUT VOLTAGE vs. SUPPLY VOLTAGE
FANOUT CURRENT = 250mA
MAX6665 toc02
900 800 700 FANOUT VOLTAGE (mV) 600 500 400 300 200 100 0 10
TA = +75C VDD = +2.7V
550 500 FANOUT VOLTAGE (mV) 450 400 350 300 250
VDD = +3.3V
TA = +75C TA = +50C
VDD = +5.0V 100 FANOUT CURRENT (mA) 1000
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
SUPPLY VOLTAGE (V)
NO-LOAD SUPPLY CURRENT vs. TEMPERATURE
MAX6665 toc03
TEMPERATURE THRESHOLD DISTRIBUTION
MAX6665ASA55 100 SAMPLES 45 PERCENTAGE OF SAMPLES (%) 40 35 30 25 20 15 10 5
MAX6665 toc04
90 80 SUPPLY CURRENT (A) 70 60
FORCEON = VDD
50
VDD = +5V
VDD = +3.3V
VDD = +2.7V 50 40 30 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (C)
0
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)
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Fan Controller/Driver with FactoryProgrammed Temperature Thresholds MAX6665
Pin Description
PIN 1 2 3 4 5 6 7 8 Exposed Paddle NAME GND FORCEON HYST FANON OT WARN VDD FANOUT 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 8C, GND for 4C, and leave HYST unconnected for 1C hysteresis. 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. Overtemperature Output. Active-low when the temperature is 30C above the fan threshold. Opendrain output, requires resistive pullup. Overtemperature Warning Output. Active-low when the temperature is 15C above the fan threshold. Open-drain output, requires resistive pullup. Supply Voltage. Bypass with a 1F capacitor to GND as close to VDD pin as possible. Fan-Switch (Driver) Output. Connect to the low side of a fan. Ground FUNCTION
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 15C 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 30C 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.
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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 1C, 4C, or 8C 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 51C/W, so the die temperature
_______________________________________________________________________________________
Fan Controller/Driver with FactoryProgrammed Temperature Thresholds MAX6665
+4.5V TO +24V 100mA TO 250mA COOLING FAN
+3.3V 1F
VDD
FANOUT
VDD 100k
MAX6665
HYST WARN
I/O
P
FORCEON
FANON VDD 100k OT GND SYSTEM POWER SHUTDOWN
I/O
Figure 1. High-Reliability, Fail-Safe Fan Controller and Temperature Monitor
increases by a maximum of: 51C/W x 0.03125W = 1.59C Therefore, the effective hysteresis is about 1.59C higher than the hysteresis selected by the HYST pin. For example, setting the HYST pin for 8C of hysteresis results in an effective hysteresis of about 9.6C. 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: 51C/W x 0.150W = 7.65C If the HYST pin has been set for 8C of hysteresis, the total effective hysteresis will be about 15.7C. 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 1F 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.
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Fan Controller/Driver with FactoryProgrammed Temperature Thresholds MAX6665
Chip Information
TRANSISTOR COUNT: 1543 MOS 119 BIPOLAR PROCESS: BiCMOS
Package Information
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 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
8L, SOIC EXP. PAD.EPS

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