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19-3305; Rev 1; 8/04
Automatic PWM Fan-Speed Controllers with 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 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/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 temperatures (in 5C 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 MAX(R) package. All versions operate from 3.0V to 5.5V supply voltages and consume 500A (typ) supply current.
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 LowTemperature Fan Threshold Pin-Selectable or Factory-Selectable HighTemperature 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 2C Temperature-Measurement Accuracy FULLSPD/FULLSPD Input Sets PWM to 100% Pin-Selectable OT Output Threshold 16-Pin QSOP and 10-Pin MAX Packages
MAX6643/MAX6644/MAX6645
Applications
Networking Equipment Storage Equipment Servers Desktop Computers Workstations
PART MAX6643LBFAEE MAX6643LAFAEE* MAX6643LBBAEE MAX6643LABAEE* MAX6643HAFAEE* MAX6644LBAAEE MAX6644HAFAEE*
Ordering Information
TEMP RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 16 QSOP 16 QSOP 16 QSOP 16 QSOP 16 QSOP 16 QSOP 16 QSOP 10 MAX 10 MAX
Pin Configurations, Typical Operating Circuit, and Selector Guide appear at end of data sheet. MAX is a registered trademark of Maxim Integrated Products, Inc.
MAX6645ABFAUB* MAX6645BAFAUB
*Future product--contact factory for availability.
________________________________________________________________ Maxim Integrated Products
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Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
ABSOLUTE MAXIMUM RATINGS
VDD to 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 +(VDD + 0.3V) FANFAIL, OT Current ..........................................-1mA to +50mA Continuous Power Dissipation (TA = +70C) 10-Pin MAX (derate 5.6mW/C above +70C) ...........444mW 16-Pin QSOP (derate 8.3mW/C above +70C).......... 667mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C 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 = +3.0V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at VDD = +3.3V, TA = +25C.) (Note 1)
PARAMETER Operating Supply Voltage Range Remote Temperature Error SYMBOL VDD VDD = +3.3V, +20C TRJ +100C VCC = +3.3V TA = +20C to +60C TA = 0C to +125C TA = +10C to +70C TA = 0C to +125C 0.2 VDD falling edge IS During a conversion Duty cycle = 50%, no load High level MAX664_ _A_ _ _ _ MAX664_ _B_ _ _ _ MAX664_ _A_ _ _ _ MAX664_ _B_ _ _ _ 80 100 125 2.5 8 2.5 0.5 16 FPWM_OUT VOL VOL IOH ISINK = 1mA ISINK = 6mA ISINK = 1mA VOH = 3.3V 32 0.4 0.5 0.4 1 1.5 2.0 90 0.5 1 0.5 120 2.5 CONDITIONS MIN +3.0 TYP MAX +5.5 2 C 3 2.5 3.5 C C/V V mV mA mA A ms s s Hz Hz V V A UNITS V
Local Temperature Error Temperature Error from Supply Sensitivity Power-On-Reset (POR) Threshold POR Threshold Hysteresis Operating Current Average Operating Current Remote-Diode Sourcing Current Conversion Time Spin-Up Time Startup Delay Minimum Fan-Fail Tachometer Frequency PWM_OUT Frequency Output Low Voltage (OT) Output Low Voltage (FANFAIL, PWM_OUT) Output-High Leakage Current DIGITAL OUTPUTS (OT, FANFAIL, PWM_OUT)
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Automatic PWM Fan-Speed Controllers with Overtemperature Output
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +3.0V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at VDD = +3.3V, TA = +25C.) (Note 1)
PARAMETER SYMBOL VDD = 5.5V VDD = 3.0V VDD = 3.0V VIN = GND or VDD -1 CONDITIONS MIN 3.65 2.2 0.8 +1 TYP MAX UNITS DIGITAL INPUTS (FULLSPD, FULLSPD, TACHSET) Logic-Input High Logic-Input Low Input Leakage Current VIH VIL V V A
MAX6643/MAX6644/MAX6645
Note 1: All parameters tested at TA = +25C. Specifications over temperature are guaranteed by design.
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
OPERATING SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6643 toc01
PWMOUT FREQUENCY vs. DIE TEMPERATURE
MAX6643 toc02
400
32.0
320
PWMOUT FREQUENCY (Hz) 3.0 3.5 4.0 4.5 5.0 5.5
360 SUPPLY CURRENT (A)
31.8
31.6
280
31.4
240
31.2
200 SUPPLY VOLTAGE (V)
31.0 -40 -15 10 35 60 85 100 TEMPERATURE (C)
PWMOUT FREQUENCY vs. SUPPLY VOLTAGE
MAX6643 toc03
TRIP-THRESHOLD ERROR vs. TRIP TEMPERATURE
MAX664_L VERSIONS
MAX6643 toc04
35
1.0
PWMOUT FREQUENCY (Hz)
34
TRIP-THRESHOLD ERROR (C)
0.6
33
0.2
32
-0.2
31
-0.6
30 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
-1.0 20 40 60 80 100 TRIP TEMPERATURE (C)
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Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
Pin Description
PIN MAX6643_A MAX6643_B 1, 15 1, 15 MAX6644_ 1, 15 MAX6645_ -- NAME FUNCTION High-Temperature Threshold Inputs. Connect to VDD, GND, or leave unconnected to select the upper fan-control trip temperature (THIGH), in 5C increments. See Table 1. Low-Temperature Threshold Inputs. Connect to VDD, GND, or leave unconnected to select the lower fan-control trip temperature (TLOW), in 5C increments. See Table 2. Fan-Fail Alarm Output. FANFAIL is an active-low, opendrain output. If the FAN_IN_ detects a fan failure, the FANFAIL output asserts low. FAN_IN_ Control Input. TACHSET controls what type of fanfail condition is being detected. Connect TACHSET to VDD, GND, 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. Ground
TH1, TH2
2, 3
2, 3
2, 3
--
TL2, TL1
4
4
4
1
FANFAIL
5
5
5
2
TACHSET
-- 6 7 8
6 -- 7 8
-- -- 7 --
-- -- 4 --
FULLSPD FULLSPD GND DXP
-- 9
-- 9
6, 8 9
3, 5 6
Combined Current Source and A/D Positive Input for Remote Diode. Connect to anode of remote diode-connected temperature-sensing transistor. Connect to GND if no remote diode is used. Place a 2200pF capacitor between DXP_ and DXP2, DXP1 GND for noise filtering. OT Active-Low, Open-Drain Overtemperature Output. When OT threshold is exceeded, OT pulls low. Fan-Sense Input. FAN_IN_ can be configured to monitor either a fan's logic-level locked-rotor output, tachometer output, or sense-resistor waveform to detect fan failure. The MAX6643's FAN_IN_ input can monitor only tachometer signals. The MAX6644 and the MAX6645 can monitor any one of the three signal types as configured using the TACHSET input.
10, 11
10, 11
10, 11
7, 8
FAN_IN2, FAN_IN1
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Automatic PWM Fan-Speed Controllers with Overtemperature Output
Pin Description (continued)
PIN MAX6643_A MAX6643_B MAX6644_ MAX6645_ NAME 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. Overtemperature Threshold Inputs. Connect to VDD, GND, or leave unconnected to select the upper-limit OT fault output trip temperature, in 5C increments. See Table 4. Power-Supply Input. 3.3V nominal. Bypass VDD to GND with a 0.1F capacitor.
MAX6643/MAX6644/MAX6645
12
12
12
9
PWM_OUT
13, 14
13, 14
13, 14
--
OT2, OT1
16
16
16
10
VDD
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.
the low-temperature threshold (TLOW), and the overtemperature 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 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.
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 0C. Since the larger of the two temperatures prevails, a faulty or unconnected diode is not used for calculating fan speed or determining overtemperature faults.
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
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),
High-Z = High impedance.
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Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
Table 2. Setting TLOW
(MAX6643 and MAX6644)
TL2 0 0 0 High-Z High-Z High-Z 1 1 1 TL1 0 High-Z 1 0 High-Z 1 0 High-Z 1 TLOW (C) L SUFFIX 15 20 25 30 35 40 45 50 55 TLOW (C) H SUFFIX 35 40 45 50 55 60 65 70 75
TEMPERATURE THIGH STARTUP TIME DUTY CYCLE SPIN-UP
High-Z = High impedance.
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, THIGH is set to the temperature beyond which the fan should spin at 100%. TLOW 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 THIGH, the duty cycle remains at zero (see Figure 1). If the temperature increases above THIGH, 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 THIGH 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 THIGH. For option 2 (minimum duty cycle = start duty cycle), if the measured temperature remains below THIGH, the duty cycle does not increase and the fan continues to run at a slow speed. If the temperature increases above THIGH, the duty cycle begins to increase, incrementing by 1.5% every 4s until the fan is spinning fast enough to reduce the temperature below THIGH (see Figure 2). In both cases, if only a small amount of extra cooling is necessary to reduce the temperature below
6
TLOW
TIME
Figure 1. Temperature-Controlled Duty-Cycle Change with Minimum Duty Cycle 30%
SPIN-UP
DUTY CYCLE
STARTUP MAX664_B HAS 30% PWM_OUT DUTY CYCLE DURING STARTUP.
TIME
TEMPERATURE
THIGH
TLOW
TIME
Figure 2. Temperature-Controlled Duty-Cycle Change with Minimum Duty Cycle 30%
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Automatic PWM Fan-Speed Controllers with Overtemperature Output
THIGH, the duty cycle may increase just a few percent above the minimum duty cycle. If the power dissipation or ambient temperature increases to a high-enough value, the duty cycle may eventually need to increase to 100%. If the ambient temperature or the power dissipation reduces to the point that the measured temperature is less than TLOW, the duty cycle begins slowly decrementing until either the duty cycle reaches its minimum value or the temperature rises above TLOW. The small duty-cycle increments and slow rate-ofchange of duty cycle (1.5% maximum per 4s) reduce the likelihood that the process of fan-speed control is acoustically objectionable. The "dead band" between TLOW and THIGH keeps the fan speed constant when the temperature is undergoing small changes, thus making the fan-control process even less audible. with this detection method, there may be some that do not produce reliable tachometer signals. If a 2-wire fan is to be used with fault detection, be sure that the fan is compatible with this technique. To detect fan failure, the analog sense-conditioned pulses or the tachometer pulses are deglitched and counted for 2s while the duty cycle is 100% (either during spin-up or when the duty cycle rises to 100% due to measured temperature). If more than 32 pulses are counted (corresponding to 480rpm for a fan that produces two pulses per revolution), the fan is assumed to be functioning normally. If fewer than 32 pulses are received, the FANFAIL output is enabled and the PWM duty cycle to the FET transistor is either shut down in case of a single-fan (MAX6643) configuration or continues normal operation in case of a dual-fan configuration (MAX6644/MAX6645). Some fans have a locked-rotor logic output instead of a tachometer output. If a locked-rotor signal is to be used to detect fan failure, that signal is monitored for 2s while the duty cycle is 100%. If a locked-rotor signal remains active (low) for more than 2s, the fan is assumed to have failed. The MAX6643/MAX6644/MAX6645 have two channels for monitoring fan-failure signals, FAN_IN1 and FAN_IN2. For the MAX6643, the FAN_IN_ channels monitor a tachometer. The MAX6643's fault sensing can also be turned off by floating the TACHSET input. For the MAX6644 and MAX6645, the FAN_IN1 and FAN_IN2 channels can be configured to monitor either a logic-level tachometer signal, the voltage waveform on a current-sense resistor, or a locked-rotor logic signal. The TACHSET input selects which type of signal is to be monitored (see Table 3). To disable fan-fault sensing, TACHSET should be unconnected and FAN_IN1 and FAN_IN2 should be connected to VDD.
MAX6643/MAX6644/MAX6645
Fan-Fail Sensing
The MAX6643/MAX6644/MAX6645 feature a FANFAIL output. The FANFAIL output is an active-low, opendrain alarm. The MAX6643/MAX6644/MAX6645 detect fan failure either by measuring the fan's speed and recognizing when it is too low, or by detecting a lockedrotor logic signal from the fan. Fan-failure detection is enabled only when the duty cycle of the PWM drive signal is equal to 100%. This happens during the spin-up period when the fan first turns on and whenever the temperature is above THIGH long enough that the duty cycle reaches 100%. Many fans have open-drain tachometer outputs that produce periodic pulses (usually two pulses per revolution) as the fan spins. These tachometer pulses are monitored by the FAN_IN_ inputs to detect fan failures. If a 2-wire fan with no tachometer output is used, the fan's speed can be monitored by using an external sense resistor at the source of the driving FET (see Figure 3). In this manner, the variation in the current flowing through the fan develops a periodic voltage waveform across the sense resistor. This periodic waveform is then highpass filtered and AC-coupled to the FAN_IN input. Any variations in the waveform that have an amplitude of more than 150mV are converted to digital pulses. The frequency of these digital pulses is directly related to the speed of the rotation of the fan and can be used to detect fan failure. Note that the value of the sense resistor must be matched to the characteristics of the fan's current waveform. Choose a resistor that produces voltage variations of at least 200mV to ensure that the fan's operation can be reliably detected. Note that while most fans have current waveforms that can be used
OT Output
The MAX6643/MAX6644/MAX6645 include an overtemperature output that can be used as an alarm or a system-shutdown signal. Whenever the measured temperature exceeds the value selected using the OT programming inputs OT1 and OT2 (see Table 4), OT is asserted. OT deasserts only after the temperature drops below the threshold.
FULLSPD Input
The MAX6643_A_ features a FULLSPD input. Pulling FULLSPD low forces PWM_OUT to 100% duty cycle. The FULLSPD input allows a microcontroller to force the fan to full speed when necessary. It also allows a FANFAIL output to force other fans to 100% in multifan
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Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
Table 3. Configuring the FAN_IN_ Inputs with TACHSET
TACHSET MAX6643_A_ MAX6644_A_ MAX6645_A_ MAX6643_B_ MAX6644_B_ MAX6645_B_ VDD FAN_IN1 Tachometer Tachometer Tachometer Tachometer Tachometer Tachometer FAN_IN2 Tachometer Tachometer Tachometer Tachometer Tachometer Tachometer FAN_IN1 Do not connect to GND Current sense Current sense Do not connect to GND Current sense Current sense GND FAN_IN2 Do not connect to GND Current sense Current sense Do not connect to GND Current sense Current sense UNCONNECTED FAN_IN1 Disables fanfailure detection Locked rotor Locked rotor Disables fanfailure detection Locked rotor Locked rotor FAN_IN2 Disables fanfailure detection Locked rotor Locked rotor Disables fanfailure detection Locked rotor Locked rotor
Table 4. Setting the Overtemperature Thresholds (TOVERT) (MAX6643 and MAX6644)
OT2 0 0 0 High-Z High-Z High-Z 1 1 1 OT1 0 High-Z 1 0 High-Z 1 0 High-Z 1 TOVERT (C) L SUFFIX 60 65 70 75 80 85 90 95 100 TOVERT (C) H SUFFIX 80 85 90 95 100 105 110 115 120
Table 5. Remote-Sensor Transistor Manufacturers
MANUFACTURER Central Semiconductor (USA) Rohm Semiconductor (USA) Samsung (Korea) Siemens (Germany) MODEL NO. CMPT3906 SST3906 KST3906-TF SMBT3906
High-Z = High impedance
systems, or for an over-temperature condition (by connecting OT to FULLSPD).
FULLSPD Input
The MAX6643_B_ features a FULLSPD input. Pulling FULLSPD high forces PWM_OUT to 100% duty cycle. The FULLSPD input allows a microcontroller to force the fan to full speed when necessary. By connecting FANFAIL to an inverter, the MAX6643_B_ can force other fans to 100% in multifan systems, or for an overtemperature condition (by connecting OT inverter to FULLSPD).
signal transistors, some of which are listed in Table 5. The MAX6643/MAX6644/MAX6645 can also directly measure the die temperature of CPUs and other ICs with on-board temperature-sensing diodes. The transistor must be a small-signal type with a relatively high forward voltage. This ensures that the input voltage is within the ADC input voltage range. The forward voltage must be greater than 0.25V at 10A at the highest expected temperature. The forward voltage must be less than 0.95V at 100A at the lowest expected temperature. The base resistance has to be less than 100. Tight specification of forward-current gain (+50 to +150, for example) indicates that the manufacturer has good process control and that the devices have consistent characteristics.
Effect of Ideality Factor
The accuracy of the remote temperature measurements depends on the ideality factor (n) of the remote diode (actually a transistor). The MAX6643/MAX6644/ MAX6645 are optimized for n = 1.01, which is typical of many discrete 2N3904 and 2N3906 transistors. It is also near the ideality factors of many widely available CPUs, GPUs, and FPGAs. However, any time a sense transistor with a different ideality factor is used, the output data is different. Fortunately, the difference is predictable.
Applications Information
Figures 3-6 show various configurations.
Remote-Diode Considerations
When using an external thermal diode, temperature accuracy depends upon having a good-quality, diodeconnected, small-signal transistor. Accuracy has been experimentally verified for a variety of discrete small8
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Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
VDD (+3.0V TO +5.5V) +VFAN (5V OR 12V) +VFAN (5V OR 12V)
1 4.7k 2
TH1 TL2
VDD TH2
16 15
3 TO FANFAIL ALARM 4
TL1 FANFAIL
MAX6644
OT1 OT2
14 13
4.7k
4.7k N N
5
TACHSET
PWM_OUT
12 CURRENT-SENSE 0.1F MODE CURRENT-SENSE MODE 0.1F
6 7
DXP2 GND
FAN_IN1 FAN_IN2
11 10
8
DXP1
OT
9 TO OVERTEMPERATURE ALARM
2.0
2.0
Figure 3. MAX6644 Using Two External Transistors to Measure Remote Temperatures and Control Two 2-Wire Fans. The fan's powersupply current is monitored to detect failure of either fan. Connect pin 10 to pin 11 if only one fan is used.
VDD (+3.0V TO +5.5V) +VFAN (5V OR 12V) +VFAN (5V OR 12V)
4.7k TO FANFAIL ALARM 1 FANFAIL VDD 10
4.7k
4.7k
2 3 4
TACHSET DXP2 GND
PWM_OUT
9
N TACHOMETER MODE TACHOMETER MODE
MAX6645 FAN_IN1
FAN_IN2
8 7
5
DXP1
OT
6
TO OVERTEMPERATURE ALARM
Figure 4. MAX6645 Using Two External Transistors to Measure Remote Temperatures and Control Two 2-Wire Cooling Fans. The fan's power-supply current is monitored to detect failure of either fan. Connect FAN_IN1 to FAN_IN2 if only one fan is used. _______________________________________________________________________________________ 9
Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
+VFAN (5V OR 12V)
VDD (+3.0V TO +5.5V)
4.7k TO FANFAIL ALARM 10 9 TACHOMETER 8 MODE TACHOMETER 7 MODE 6 4.7k 4.7k
1 2 3 4 5
FANFAIL TACHSET DXP2 GND DXP1 MAX6645
VDD PWM_OUT FAN_IN1 FAN_IN2 OT
N
TO OVERTEMPERATURE ALARM
Figure 5. Using the MAX6645 to Monitor Two Fans
10
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Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
+VFAN (5V OR 12V) VDD (+3.0V TO +5.5V)
1 2 4.7k 3 4 TO FANFAIL ALARM 5 6 7 8
TH1 TL2 TL1 FANFAIL TACHSET FULLSPD GND DXP MAX6643_A_
VDD TH2 OT1 OT2 PWM_OUT FAN_IN1 FAN_IN2 OT
16 15 14 13 12 11 (TACHOMETER MODE) 10 (TACHOMETER MODE) 9 4.7k 4.7k
N
TO OVERTEMPERATURE ALARM +VFAN (5V OR 12V)
VDD (+3.0V TO +5.5V)
1 2 4.7k 3 4 5 6 7
TH1 TL2 TL1 FANFAIL TACHSET FULLSPD GND MAX6643_A_
VDD TH2 OT1 OT2 PWM_OUT FAN_IN1 FAN_IN2
16 15 14 13 12 11 (TACHOMETER MODE) 10 (TACHOMETER MODE) 4.7k 4.7k
TO FANFAIL ALARM
N
8
DXP
OT
9
TO OVERTEMPERATURE ALARM
Figure 6. Using Two MAX6643s, Each Controlling a Separate Fan ______________________________________________________________________________________ 11
Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
Assume a remote-diode sensor designed for a nominal ideality factor nNOMINAL is used to measure the temperature of a diode with a different ideality factor, n1. The measured temperature TM can be corrected using: n1 TM = TACTUAL nNOMINAL where temperature is measured in Kelvin. As mentioned above, the nominal ideality factor of the MAX6643/MAX6644/MAX6645 is 1.01. As an example, assume the MAX6643/MAX6644/MAX6645 are configured with a CPU that has an ideality factor of 1.008. If the diode has no series resistance, the measured data is related to the real temperature as follows:
n 1.01 TACTUAL = TM NOMINAL = TM = TM (1.00198) 1.008 n1
In this example, the effect of the series resistance and the ideality factor partially cancel each other. For best accuracy, the discrete transistor should be a small-signal device with its collector connected to base, and emitter connected to GND. Table 5 lists examples of discrete transistors that are appropriate for use with the MAX6643/MAX6644/MAX6645. The transistor must have a relatively high forward voltage; otherwise, the ADC input voltage range can be violated. The forward voltage at the highest expected temperature must be greater than 0.25V at 10A, and at the lowest expected temperature, the forward voltage must be less than 0.95V at 100A. Large power transistors must not be used. Also, ensure that the base resistance is less than 100. Tight specifications for forward current gain (50 < <150, for example) indicate that the manufacturer has good process controls and that the devices have consistent VBE characteristics.
For a real temperature of +60C (333.15K), the measured temperature is 59.33C (332.49K), which is an error of -0.66C.
ADC Noise Filtering
The integrating ADC has inherently good noise rejection, especially of low-frequency signals such as 60Hz/120Hz power-supply hum. Micropower operation places constraints on high-frequency noise rejection. Lay out the PC board carefully with proper external noise filtering for high-accuracy remote measurements in electrically noisy environments. Filter high-frequency electromagnetic interference (EMI) at the DXP pins with an external 2200pF capacitor connected between DXP, DXP1, or DXP2 and ground. This capacitor can be increased to about 3300pF (max), including cable capacitance. A capacitance higher than 3300pF introduces errors due to the rise time of the switched-current source.
Effect of Series Resistance
Series resistance in a sense diode contributes additional errors. For nominal diode currents of 10A and 100A, change in the measured voltage is: VM = RS (100A -10A ) = 90A x Rs Since 1C corresponds to 198.6V, series resistance contributes a temperature offset of: V C = 0.453 V 198.6 C 90 Assume that the diode being measured has a series resistance of 3. The series resistance contributes an offset of: 3 x 0.453 C = 1.36C
Twisted Pairs and Shielded Cables
For remote-sensor distances longer than 8in, or in particularly noisy environments, a twisted pair is recommended. Its practical length is 6ft to 12ft (typ) before noise becomes a problem, as tested in a noisy electronics laboratory. For longer distances, the best solution is a shielded twisted pair like that used for audio microphones. For example, Belden 8451 works well for distances up to 100ft in a noisy environment. Connect the twisted pair to DXP and GND and the shield to ground, and leave the shield's remote end unterminated. Excess capacitance at DXP limits practical remote-sensor distances (see the Typical Operating Characteristics). For very long cable runs, the cable's parasitic capacitance often provides noise filtering, so the recommended 2200pF capacitor can often be removed or reduced
The effects of the ideality factor and series resistance are additive. If the diode has an ideality factor of 1.008 and series resistance of 3, the total offset can be calculated by adding error due to series resistance with error due to ideality factor: 1.36C - 0.66C = 0.7C for a diode temperature of +60.7C.
12
______________________________________________________________________________________
Automatic PWM Fan-Speed Controllers with Overtemperature Output
in value. Cable resistance also affects remote-sensor accuracy. A 1 series resistance introduces about +1/2C error. 5) When introducing a thermocouple, make sure that both the DXP and the GND paths have matching thermocouples. In general, PC board-induced thermocouples are not a serious problem. A copper solder thermocouple exhibits 3V/C, and it takes approximately 200V of voltage error at DXP/GN to cause a +1C measurement error, so most parasitic thermocouple errors are swamped out. 6) Use wide traces. Narrow traces are more inductive and tend to pick up radiated noise. The 10-mil widths and spacings are recommended, but are not absolutely necessary (as they offer only a minor improvement in leakage and noise), but use them where practical. 7) Placing an electrically clean copper ground plane between the DXP traces and traces carrying highfrequency noise signals helps reduce EMI.
MAX6643/MAX6644/MAX6645
PC Board Layout Checklist
1) Place the MAX6643/MAX6644/MAX6645 as close as practical to the remote diode. In a noisy environment, such as a computer motherboard, this distance can be 4in to 8in or more, as long as the worst noise sources (such as CRTs, clock generators, memory buses, and ISA/PCI buses) are avoided. 2) Do not route the DXP lines next to the deflection coils of a CRT. Also, do not route the traces across a fast memory bus, which can easily introduce +30C error, even with good filtering. Otherwise, most noise sources are fairly benign. 3) Route the DXP and GND traces parallel and close to each other, away from any high-voltage traces such as +12VDC. Avoid leakage currents from PC board contamination. A 20M leakage path from DXP to ground causes approximately +1C error. 4) Route as few vias and crossunders as possible to minimize copper/solder thermocouple effects.
Chip Information
TRANSISTOR COUNT: 12,518 PROCESS: BiCMOS
Pin Configurations
TOP VIEW
TH1 1 TL2 2 TL1 3 FANFAIL 4 TACHSET 5 FULLSPD (FULLSPD) 6 GND 7 DXP 8 16 VDD 15 TH2 14 OT1 TH1 1 TL2 2 TL1 3 FANFAIL 4 16 VDD 15 TH2 14 OT1 FANFAIL 1 TACHSET DXP2 GND DXP1 2 3 4 5 10 VDD 9 PWM_OUT FAN_IN1 FAN_IN2 OT
MAX6645_ _
8 7 6
MAX6643_A _ MAX6643_B_
13 OT2
MAX6644_ _
13 OT2 12 PWM_OUT 11 FAN_IN1 10 FAN_IN2 9 OT
12 PWM_OUT TACHSET 5 11 FAN_IN1 10 FAN_IN2 9 OT DXP2 6 GND 7 DXP1 8
MAX
QSOP
() ARE FOR MAX6643_A ONLY.
QSOP
______________________________________________________________________________________
13
Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
Selector Guide
PACKAGE-PINS MINIMUM DUTY CYCLE (%) START DUTY CYCLE (%) CHANNELS FULLSPD POLARITY STARTUP DELAY (s) FAN_IN1 FAN_IN2 Tach/off Tach/off Tach/off Tach/off Tach/off Locked rotor/tach/ current sense Locked rotor/tach/ current sense Locked rotor/tach/ current sense Locked rotor/tach/ current sense SPIN-UP TIME (s) OT (C) 60 to 100 60 to 100 60 to 100 60 to 100 80 to 120 60 to 100 TH (C) 20 to 60 20 to 60 20 to 60 20 to 60 40 to 80 20 to 60 TL (C) 15 to 55 15 to 55 15 to 55 15 to 55 35 to 75 15 to 55
PART
MAX6643 LBFAEE MAX6643 LAFAEE* MAX6643 LBBAEE MAX6643 LABAEE* MAX6643H AFAEE* MAX6644 LBAAEE
QSOP-16 QSOP-16 QSOP-16 QSOP-16 QSOP-16
0.5 2.5 0.5 2.5 2.5
8 2.5 8 2.5 2.5
40 40 30 30 40
40 40 30 30 40
Remote, local Remote, local Remote, local Remote, local Remote, local Remote, remote
FULLSPD FULLSPD FULLSPD FULLSPD FULLSPD
Tach/off Tach/off Tach/off Tach/off Tach/off Locked rotor/tach/ current sense Locked rotor/tach/ current sense Locked rotor/tach/ current sense Locked rotor/tach/ current sense
QSOP-16
0.5
8
30
0
--
MAX6644H AFAEE*
QSOP-16
2.5
2.5
40
40
Remote, remote
35 to 75
40 to 80
80 to 120
--
MAX6645 MAX-10 AAFAUB*, **
0.5
8
40
40
Remote, remote
45
50
75
--
MAX6645 BAFAUB**
MAX-10
2.5
2.5
40
40
Remote, remote
55
65
120
--
*Future product--contact factory for availability. **The MAX6645xxxxxx can be ordered with any combination of TL, TH, and OT trip threshold (in 5C increments) by contacting the factory.
14
______________________________________________________________________________________
Automatic PWM Fan-Speed Controllers with Overtemperature Output
Block Diagram
FULLSPD/(FULLSPD)
MAX6643/MAX6644/MAX6645
DXP1/(DXP) DXP2 TEMPERATURE SENSOR
TEMPERATURE LOGIC
DUTY CYCLE PWM GENERATOR PWM_OUT
ANALOG SENSE TACHOMETER
MAX6643 MAX6644 MAX6645
FAN_IN1 LOCKED ROTOR IN FAN-FAIL DETECTION OT TH TL ANALOG SENSE TACHOMETER FAN_IN2 LOCKED ROTOR IN THRESHOLD SELECTION
() ARE FOR MAX6643 ONLY.
OT1 OT2 TH1 TH2 TL1 TL2
TACHSET
FANFAIL
Typical Operating Circuit
+VFAN (5V OR 12V) VDD (+3.0V TO +5.5V)
1 2 4.7k 3 4 5 6 7 8
TH1 TL2 TL1 FANFAIL TACHSET FULLSPD GND DXP MAX6643_A_
VDD TH2 OT1 OT2 PWM_OUT FAN_IN1 FAN_IN2 OT
16 15 14 13 12 11 (TACHOMETER MODE) 10 (TACHOMETER MODE) 9 4.7k 4.7k
TO FANFAIL ALARM
N
TO OVERTEMPERATURE ALARM
______________________________________________________________________________________
15
Automatic PWM Fan-Speed Controllers with Overtemperature Output MAX6643/MAX6644/MAX6645
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
QSOP.EPS
PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH
21-0055
E
1 1
16
______________________________________________________________________________________
Automatic PWM Fan-Speed Controllers with Overtemperature Output
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
10LUMAX.EPS
1 1
MAX6643/MAX6644/MAX6645
e
10
4X S
10
INCHES MAX DIM MIN 0.043 A 0.006 A1 0.002 A2 0.030 0.037 D1 0.116 0.120 D2 0.114 0.118 E1 0.116 0.120 E2 0.114 0.118 H 0.187 0.199 L 0.0157 0.0275 L1 0.037 REF b 0.007 0.0106 e 0.0197 BSC c 0.0035 0.0078 0.0196 REF S 0 6
MILLIMETERS MAX MIN 1.10 0.05 0.15 0.75 0.95 2.95 3.05 2.89 3.00 2.95 3.05 2.89 3.00 4.75 5.05 0.40 0.70 0.940 REF 0.177 0.270 0.500 BSC 0.090 0.200 0.498 REF 0 6
H 0 0.500.1 0.60.1
1
1
0.60.1
TOP VIEW
BOTTOM VIEW
D2 GAGE PLANE A2 A b A1 D1
E2
c
E1 L1
L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 10L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0061
I
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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