max6643 pwm fan speed controll

8/8/2019 MAX6643 PWM Fan Speed Controll

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General DescriptionThe MAX6643/MAX6644/MAX6645 monitor temperatureand automatically adjust fan speed to ensure optimumcooling while minimizing acoustic noise from the fan.Each device measures two temperature locations.

The MAX6643/MAX6644/MAX6645 generate a PWMwaveform that drives an external power transistor, whichin turn modulates the fans power supply. TheMAX6643/MAX6644/MAX6645 monitor temperature andadjust the duty cycle of the PWM output waveform to con-trol the fans speed according to the cooling needs of thesystem. The MAX6643 monitors its own die temperatureand an optional external transistors temperature, while theMAX6644 and MAX6645 each monitor the temperatures

of one or two external diode-connected transistors.The MAX6643 and MAX6644 have nine selectable triptemperatures (in 5C increments). The MAX6645 is fac-tory programmed and is not pin selectable.

All versions include an overtemperature output (OT).OT can be used for warning or system shutdown. TheMAX6643 also features a FULLSPD input that forces thePWM duty cycle to 100%. The MAX6643/MAX6644/MAX6645 also feature a FANFAIL output that indicatesa failed fan. See the Selector Guide for a complete listof each devices functions.

The MAX6643 and MAX6644 are available in a small16-pin QSOP package and the MAX6645 is available ina 10-pin MAX package. All versions operate from3.0V to 5.5V supply voltages and consume 500A (typ)supply current.

Applications

Networking Equipment

Storage Equipment

Servers

Desktop Computers

Workstations

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

2C Temperature-Measurement Accuracy

FULLSPD/FULLSPD Input Sets PWM to 100%

Pin-SelectableOTOutput Threshold

16-Pin QSOP and 10-Pin MAX Packages

MAX6643/MAX

6644/MAX6645

Automatic PWM Fan-Speed Controllers withOvertemperature Output

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3305; Rev 2; 3/07

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxims website at www.maxim-ic.com.

EVALUATIO

NKIT

AVAILABLE

Pin Configurations, Typical Operating Circuit, and SelectorGuide appear at end of data sheet.

PART TEMP RANGEPIN-

PACKAGE

PKG

CODE

MAX6643LBFAEE -40C to +125C 16 QSOP E16-1

MAX6643LBBAEE -40C to +125C 16 QSOP E16-1

MAX6644LBAAEE -40C to +125C 16 QSOP E16-1

MAX6645ABFAUB -40C to +125C 10 MAX U10-2

MAX is a registered trademark of Maxim Integrated Products, Inc.


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MAX6643/MAX

6644/MAX6645


2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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)

Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functionaloperation 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.

VDD to GND..............................................................-0.3V to +6V

PWM_OUT, OT, and FANFAILto 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, OTCurrent ........................... ...............-1mA to +50mA

Continuous Power Dissipation (TA = +70C)

16-Pin QSOP (derate 8.3mW/C above +70C).......... 667mW

10-Pin MAX (derate 5.6mW/C above +70C)...........444mW

Operating Temperature Range .........................-40C to +125C

Junction Temperature......................................................+150C

Storage Temperature Range ................ ............-65C to +150C

Lead Temperature (soldering, 10s) ............................ .....+300C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Operating Supply Voltage Range VDD +3.0 +5.5 V

TA = +20C to +60C 2

Remote Temperature Error

VDD = +3.3V,

+20C TRJ+100C TA = 0C to +125C 3

C

TA = +10C to +70C 2.5Local Temperature Error VCC = +3.3V

TA = 0C to +125C 3.5C

Temperature Error from Supply

Sensitivity0.2 C/V

Power-On-Reset (POR) Threshold VDD falling edge 1.5 2.0 2.5 V

POR Threshold Hysteresis 90 mV

Operating Current IS During a conversion 0.5 1 mA

Average Operating Current Duty cycle = 50%, no load 0.5 mARemote-Diode Sourcing Current High level 80 100 120 A

Conversion Time 125 ms

Spin-Up Time MAX664_ _B_ _ _ _ 8 s

Startup Delay MAX664_ _B_ _ _ _ 0.5 s

Minimum Fan-Fail Tachometer

Frequency16 Hz

PWM_OUT Frequency FPWM_OUT 32 Hz

DIGITAL OUTPUTS (OT, FANFAIL, PWM_OUT)

Output Low Voltage (OT) VOL ISINK = 1mA 0.4 V

ISINK = 6mA 0.5Output Low Voltage

(FANFAIL, PWM_OUT)VOL

ISINK = 1mA 0.4V

Output-High Leakage Current IOH VOH = 3.3V 1 A


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MAX6643/MAX

6644/MAX6645


_______________________________________________________________________________________ 3

OPERATING SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX6643toc01

SUPPLY VOLTAGE (V)

SUPPLYCURRENT(A)

5.04.54.03.5

240

280

320

360

400

2003.0 5.5

PWMOUT FREQUENCY

vs. DIE TEMPERATURE

MAX6643toc02

TEMPERATURE (C)

PWMOU

TFREQUENCY(Hz)

10085603510-15

31.2

31.4

31.6

31.8

32.0

31.0-40

TRIP-THRESHOLD ERROR

vs. TRIP TEMPERATURE

MAX6643toc04

TRIP TEMPERATURE (C)

TRIP-THRESHOLDERROR(C)

806040

-0.6

-0.2

0.2

0.6

1.0

-1.020 100

MAX664_L VERSIONS

PWMOUT FREQUENCY

vs. SUPPLY VOLTAGE

MAX6643toc03

SUPPLY VOLTAGE (V)

PWMOUTFREQUENCY(Hz)

5.04.54.03.5

31

32

33

34

35

303.0 5.5

Typical Operating Characteristics(TA = +25C, unless otherwise noted.)

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 CONDITIONS MIN TYP MAX UNITS

DIGITAL INPUTS (FULLSPD, FULLSPD, TACHSET)

VDD = 5.5V 3.65Logic-Input High VIH

VDD = 3.0V 2.2V

Logic-Input Low VIL VDD = 3.0V 0.8 V

Input Leakage Current VIN = GND or VDD -1 +1 A

Note 1: All parameters tested at TA = +25C. Specifications over temperature are guaranteed by design.


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MAX6643/MAX

6644/MAX6645


4 _______________________________________________________________________________________

Pin Description

PIN

MAX6643 MAX6644 MAX6645NAME FUNCTION

1, 15 1, 15 TH1, TH2

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.

2, 3 2, 3 TL2, TL1

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.

4 4 1 FANFAIL

Fan-Fail Alarm Output. FANFAILis an active-low, open-drain

output. If the FAN_IN_ detects a fan failure, the FANFAILoutput

asserts low.

5 5 2 TACHSET

FAN_IN_ Control Input. TACHSET controls what type of fan-fail

condition is being detected. Connect TACHSET to VDD, GND,

or leave floating to set locked rotor, current sense, or

tachometer configurations (see Table 3).

6 FULLSPDActive-High Logic Input. When pulled high, the fan runs at

100% duty cycle.

FULLSPDActive-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

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

GND for noise filtering.

9 9 6 OTActive-Low, Open-Drain Overtemperature Output. When OT

threshold is exceeded, OTpulls low.

10, 11 10, 11 7, 8FAN_IN2,

FAN_IN1

Fan-Sense Input. FAN_IN_ can be configured to monitor either a

fans logic-level locked-rotor output, tachometer output, or sense-

resistor waveform to detect fan failure. The MAX6643s 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.


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Detailed DescriptionThe MAX6643/MAX6644/MAX6645 measure temperatureand automatically adjust fan speed to ensure optimumcooling while minimizing acoustic noise from the fan.

The MAX6643/MAX6644/MAX6645 generate a PWMwaveform that drives an external power transistor,which in turn modulates the fans power supply. TheMAX6643/MAX6644/MAX6645 monitor temperature andadjust the duty cycle of the PWM output waveform tocontrol the fans speed according to the cooling needsof the system. The MAX6643 monitors its own die tem-

perature and an optional external transistors tempera-ture, while the MAX6644 and MAX6645 each monitorthe temperatures of one or two external diode-connect-ed transistors.

Temperature SensorThe pn junction-based temperature sensor can mea-sure temperatures up to two pn junctions. TheMAX6643 measures the temperature of an externaldiode-connected transistor, as well as its internal tem-perature. The MAX6644 and MAX6645 measure thetemperature 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 leftunconnected, the temperature is read as 0C. Since thelarger of the two temperatures prevails, a faulty orunconnected diode is not used for calculating fanspeed or determining overtemperature faults.

PWM OutputThe larger of the two measured temperatures is alwaysused for fan control. The temperature is compared tothree thresholds: the high-temperature threshold (THIGH),

the low-temperature threshold (TLOW), and the overtem-perature threshold, OT. The OTcomparison is done onceper second, whereas the comparisons with fan-controlthresholds 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 measuredexceeds the threshold THIGH, the PWM_OUT duty cycleis incremented by one step, i.e., approximately 1.5%(100/64). Similarly, if the temperature measured is belowthe threshold TLOW, the duty cycle is decremented byone 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 show the C value assigned to the TH_and TL_ input combinations.

MAX6643/MAX

6644/MAX6645


_______________________________________________________________________________________ 5

Pin Description (continued)

PIN

MAX6643 MAX6644 MAX6645NAME 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 VDD, GND, or

leave unconnected to select the upper-limit OTfault output trip

temperature, in 5C increments. See Table 4.

16 16 10 VDDPower-Supply Input. 3.3V nominal. Bypass VDD to GND with a

0.1F capacitor.

TH2 TH1THIGH (C)

L SUFFIX

THIGH (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 THIGH(MAX6643 and MAX6644)

High-Z = High impedance.


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MAX6643/MAX

6644/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 cyclegoes to 100% for the spin-up period. After the startupdelay and spin-up, the duty cycle drops to its minimumvalue. The minimum duty cycle is in the 0% to 50%range (see the Selector Guide).

To control fan speed based on temperature, THIGH isset to the temperature beyond which the fan should spin

at 100%. TLOW is set to the temperature below whichthe duty cycle can be reduced to its minimum value.After power-up and spin-up (if applicable), the dutycycle reduces to its minimum value (either 0% or thestart duty cycle). For option 1 (minimum duty cycle = 0),if the measured temperature remains below THIGH, theduty cycle remains at zero (see Figure 1). If the temper-ature increases above THIGH, the duty cycle goes to100% for the spin-up period, and then goes to the startduty cycle (for example, 40%). If the measured temper-ature remains above THIGH when temperature is nextmeasured (4s later), the duty cycle begins to increase,incrementing by 1.5% every 4s until the fan is spinningfast enough to reduce the temperature below THIGH.

For option 2 (minimum duty cycle = start duty cycle), ifthe measured temperature remains below THIGH, theduty cycle does not increase and the fan continues torun at a slow speed. If the temperature increasesabove THIGH, the duty cycle begins to increase, incre-menting by 1.5% every 4s until the fan is spinning fastenough to reduce the temperature below THIGH (seeFigure 2). In both cases, if only a small amount of extracooling is necessary to reduce the temperature below


6 _______________________________________________________________________________________

Table 2. Setting TLOW(MAX6643 and MAX6644)

STARTUP

DUTYCYCLE

TEMPERATURE

TIME

TIME

THIGH

SPIN-UP

TLOW

Figure 1. Temperature-Controlled Duty-Cycle Change withMinimum Duty Cycle 30%

STARTUP

MAX664_B HAS 30% PWM_OUT DUTY CYCLE DURING STARTUP.

DUTYCYCLE

TEMPERATURE

TIME

TIME

THIGH

TLOW

SPIN-UP

Figure 2. Temperature-Controlled Duty-Cycle Change withMinimum Duty Cycle 30%

TL2 TL1TLOW (C)

L SUFFIX

0 0 15

0 High-Z 20

0 1 25

High-Z 0 30

High-Z High-Z 35

High-Z 1 40

1 0 45

1 High-Z 50

1 1 55High-Z = High impedance.


7/17

THIGH, the duty cycle may increase just a few percent

above the minimum duty cycle. If the power dissipation orambient temperature increases to a high-enough value,the duty cycle may eventually need to increase to 100%.

If the ambient temperature or the power dissipationreduces to the point that the measured temperature isless than TLOW, the duty cycle begins slowly decre-menting until either the duty cycle reaches its minimumvalue or the temperature rises above TLOW.

The small duty-cycle increments and slow rate-of-change of duty cycle (1.5% maximum per 4s) reducethe likelihood that the process of fan-speed control isacoustically objectionable. The dead band betweenTLOW and THIGH keeps the fan speed constant whenthe temperature is undergoing small changes, thusmaking the fan-control process even less audible.

Fan-Fail SensingThe MAX6643/MAX6644/MAX6645 feature a FANFAILoutput. The FANFAIL output is an active-low, open-drain alarm. The MAX6643/MAX6644/MAX6645 detectfan failure either by measuring the fans speed and rec-ognizing when it is too low, or by detecting a locked-rotor logic signal from the fan. Fan-failure detection isenabled only when the duty cycle of the PWM drive sig-nal is equal to 100%. This happens during the spin-upperiod when the fan first turns on and whenever thetemperature is above THIGH long enough that the dutycycle reaches 100%.

Many fans have open-drain tachometer outputs thatproduce periodic pulses (usually two pulses per revolu-tion) as the fan spins. These tachometer pulses aremonitored by the FAN_IN_ inputs to detect fan failures.If a 2-wire fan with no tachometer output is used, thefans speed can be monitored by using an externalsense resistor at the source of the driving FET (seeFigure 3). In this manner, the variation in the currentflowing through the fan develops a periodic voltagewaveform across the sense resistor. This periodicwaveform is then highpass filtered and AC-coupled tothe FAN_IN_ input. Any variations in the waveform thathave an amplitude of more than 150mV are convertedto digital pulses. The frequency of these digital pulses

is directly related to the speed of the rotation of the fanand can be used to detect fan failure.

Note that the value of the sense resistor must bematched to the characteristics of the fans currentwaveform. Choose a resistor that produces voltagevariations of at least 200mV to ensure that the fansoperation can be reliably detected. Note that whilemost fans have current waveforms that can be usedwith 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 iscompatible with this technique.

To detect fan failure, the analog sense-conditionedpulses or the tachometer pulses are deglitched andcounted for 2s while the duty cycle is 100% (either dur-ing spin-up or when the duty cycle rises to 100% due tomeasured temperature). If more than 32 pulses arecounted (corresponding to 480rpm for a fan that pro-duces two pulses per revolution), the fan is assumed tobe functioning normally. If fewer than 32 pulses arereceived, the FANFAIL output is enabled and the PWMduty cycle to the FET transistor is either shut down incase of a single-fan (MAX6643) configuration or contin-ues normal operation in case of a dual-fan configuration

(MAX6644/MAX6645).Some fans have a locked-rotor logic output instead of atachometer output. If a locked-rotor signal is to be usedto detect fan failure, that signal is monitored for 2s whilethe duty cycle is 100%. If a locked-rotor signal remainsactive (low) for more than 2s, the fan is assumed tohave failed.

The MAX6643/MAX6644/MAX6645 have two channelsfor monitoring fan-failure signals, FAN_IN1 andFAN_IN2. For the MAX6643, the FAN_IN_ channelsmonitor a tachometer. The MAX6643s fault sensing canalso 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 eithera logic-level tachometer signal, the voltage waveformon a current-sense resistor, or a locked-rotor logic sig-nal. The TACHSET input selects which type of signal isto be monitored (see Table 3). To disable fan-faultsensing, TACHSET should be unconnected andFAN_IN1 and FAN_IN2 should be connected to VDD.

OTOutputThe MAX6643/MAX6644/MAX6645 include an over-temperature output that can be used as an alarm or asystem-shutdown signal. Whenever the measured tem-perature exceeds the value selected using the OT pro-gramming inputs OT1 and OT2 (see Table 4), OT isasserted. OT deasserts only after the temperaturedrops below the threshold.

FULLSPD InputThe MAX6643 features a FULLSPD input. Pulling FULL-SPD high forces PWM_OUT to 100% duty cycle. TheFULLSPD input allows a microcontroller to force the fanto full speed when necessary. By connecting FANFAILto an inverter, the MAX6643 can force other fans to100% in multifan systems, or for an over-temperaturecondition (by connecting OT inverter to FULLSPD).

MAX6643/MAX

6644/MAX6645


_______________________________________________________________________________________ 7


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MAX6643/MAX

6644/MAX6645

Applications InformationFigures 36 show various configurations.

Remote-Diode ConsiderationsWhen using an external thermal diode, temperatureaccuracy depends upon having a good-quality, diode-connected, small-signal transistor. Accuracy has beenexperimentally verified for a variety of discrete small-signal transistors, some of which are listed in Table 5.The MAX6643/MAX6644/MAX6645 can also directlymeasure the die temperature of CPUs and other ICswith on-board temperature-sensing diodes.

The transistor must be a small-signal type with a rela-tively high forward voltage. This ensures that the input

voltage is within the ADC input voltage range. The for-ward voltage must be greater than 0.25V at 10A at thehighest expected temperature. The forward voltagemust be less than 0.95V at 100A at the lowest expect-ed temperature. The base resistance has to be lessthan 100. Tight specification of forward-current gain(+50 to +150, for example) indicates that the manufac-turer has good process control and that the deviceshave consistent characteristics.

Effect of Ideality FactorThe accuracy of the remote temperature measurementsdepends on the ideality factor (n) of the remote diode(actually a transistor). The MAX6643/MAX6644/MAX6645are optimized for n = 1.01, which is typical of many dis-crete 2N3904 and 2N3906 transistors. It is also near theideality factors of many widely available CPUs, GPUs, andFPGAs. However, any time a sense transistor with a differ-ent ideality factor is used, the output data is different.

Fortunately, the difference is predictable. Assume aremote-diode sensor designed for a nominal ideality fac-tor nNOMINAL is used to measure the temperature of adiode with a different ideality factor, n1. The measuredtemperature TM can be corrected using:

where temperature is measured in Kelvin.

As mentioned above, the nominal ideality factor of theMAX6643/MAX6644/MAX6645 is 1.01. As an example,assume the MAX6643/MAX6644/MAX6645 are config-

ured with a CPU that has an ideality factor of 1.008. Ifthe diode has no series resistance, the measured datais related to the real temperature as follows:

For a real temperature of +60C (333.15K), the mea-sured temperature is 59.33C (332.49K), which is anerror of -0.66C.

T Tn

nT

1.01

1.008TACTUAL M

NOMINAL

1M M=

=

= ( ).1 00198

T Tn

nM ACTUAL

1

NOMINAL=


8 _______________________________________________________________________________________

MANUFACTURER MODEL NO.

Central Semiconductor (USA) CMPT3906Rohm Semiconductor (USA) SST3906

Samsung (Korea) KST3906-TF

Siemens (Germany) SMBT3906

Table 5. Remote-Sensor TransistorManufacturers

OT2 OT1TOVERT (C)

L SUFFIX

0 0 60

0 High-Z 65

0 1 70

High-Z 0 75

High-Z High-Z 80

High-Z 1 85

1 0 90

1 High-Z 95

1 1 100

Table 4. Setting the OvertemperatureThresholds (TOVERT) (MAX6643 and MAX6644)

Table 3. Configuring the FAN_IN_ Inputs with TACHSET

VDD GND UNCONNECTEDTACHSET

FAN_IN1 FAN_IN2 FAN_IN1 FAN_IN2 FAN_IN1 FAN_IN2

MAX6643 Tachometer TachometerDo not connect

to GND

Do not connect

to GND

Disables fan-

failure detection

Disables fan-

failure detection

MAX6644 Tachometer Tachometer Current sense Current sense Locked rotor Locked rotor

MAX6645 Tachometer Tachometer Current sense Current sense Locked rotor Locked rotor

High-Z = high impedance


9/17

MAX6643/MAX

6644/MAX6645


_______________________________________________________________________________________ 9

MAX6644

1

2

3

4

TH1

TL2

TL1

FANFAIL

TACHSET

DXP2

GND

DXP1

VDD

TH2

OT1

OT2

PWM_OUT

FAN_IN1

FAN_IN2

OT

5

6

7

8

16

15

4.7k 4.7k

+VFAN (5V OR 12V)VDD (+3.0V TO +5.5V) +VFAN (5V OR 12V)

2.0 2.0

4.7k

TO FANFAIL

ALARM

0.1F

0.1F

14

13

CURRENT-SENSEMODE

CURRENT-SENSEMODE

TO OVERTEMPERATUREALARM

12

11

10

9

N

N

MAX6645

1FANFAIL

TACHSET

DXP2

GND

DXP1

VDD

PWM_OUT

FAN_IN1

FAN_IN2

OT

2

3

4

5

4.7k 4.7k

+VFAN (5V OR 12V)VDD (+3.0V TO +5.5V) +VFAN (5V OR 12V)

4.7k

TO FANFAIL

ALARM

10

TACHOMETER MODE

TACHOMETER MODE

TO OVERTEMPERATUREALARM

9

8

7

6

N

Figure 3. MAX6644 Using Two External Transistors to Measure Remote Temperatures and Control Two 2-Wire Fans. The fans power-supply current is monitored to detect failure of either fan. Connect pin 10 to pin 11 if only one fan is used.

Figure 4. MAX6645 Using Two External Transistors to Measure Remote Temperatures and Control Two 2-Wire Cooling Fans. Thefans power-supply current is monitored to detect failure of either fan. Connect FAN_IN1 to FAN_IN2 if only one fan is used.


10/17

MAX6643/MAX

6644/MAX6645


10 ______________________________________________________________________________________

TO FANFAILALARM

MAX6645

10

N9

8TACHOMETERMODE

TACHOMETER

MODE

TO OVERTEMPERATURE ALARM

7

6

FANFAIL

TACHSET

DXP2

GND

DXP1

VDD

VDD (+3.0V TO +5.5V)

+VFAN (5V OR 12V)

1

2

3

4

5

PWM_OUT

FAN_IN1

FAN_IN2

OT

4.7k

4.7k

4.7k

Figure 5. Using the MAX6645 to Monitor Two Fans


11/17

MAX6643/MAX

6644/MAX6645


______________________________________________________________________________________ 11

MAX6643

TH116

15

14

13

12

11 (TACHOMETER MODE)

(TACHOMETER MODE)


10

9

TL2

TL1

FANFAILTO FANFAILALARM

TO FANFAILALARM

TACHSET

FULLSPD

GND

DXP

VDD

VDD (+3.0V TO +5.5V)

+VFAN (5V OR 12V)

1

2

3

4

5

6

7

8

TH2

OT1

OT2

PWM_OUT

FAN_IN1

FAN_IN2

OT

4.7k

4.7k

4.7k

N

N

MAX6643

TH116

15

14

13

12


(TACHOMETER MODE)


10

9

TL2

TL1

FANFAIL

TACHSET

FULLSPD

GND

DXP

VDD

VDD (+3.0V TO +5.5V)

+VFAN (5V OR 12V)

1

2

3

4

5

6

7

8

TH2

OT1

OT2

PWM_OUT

FAN_IN1

FAN_IN2

OT

4.7k

4.7k

4.7k

Figure 6. Using Two MAX6643s, Each Controlling a Separate Fan


12/17

MAX6643/MAX

6644/MAX6645


12 ______________________________________________________________________________________

Effect of Series Resistance

Series resistance in a sense diode contributes addition-al errors. For nominal diode currents of 10A and100A, change in the measured voltage is:

Since 1C corresponds to 198.6V, series resistancecontributes a temperature offset of:

Assume that the diode being measured has a seriesresistance of 3. The series resistance contributes anoffset of:

The effects of the ideality factor and series resistanceare additive. If the diode has an ideality factor of 1.008and series resistance of 3, the total offset can be cal-culated by adding error due to series resistance witherror due to ideality factor:

1.36C - 0.66C = 0.7C

for a diode temperature of +60.7C.

In this example, the effect of the series resistance andthe ideality factor partially cancel each other.

For best accuracy, the discrete transistor should be asmall-signal device with its collector connected tobase, and emitter connected to GND. Table 5 listsexamples of discrete transistors that are appropriate foruse with the MAX6643/MAX6644/MAX6645.

The transistor must have a relatively high forward volt-age; otherwise, the ADC input voltage range can be vio-lated. The forward voltage at the highest expectedtemperature must be greater than 0.25V at 10A, and atthe lowest expected temperature, the forward voltagemust be less than 0.95V at 100A. Large power transis-tors must not be used. Also, ensure that the base resis-tance is less than 100. Tight specifications for forwardcurrent gain (50 <


13/17

MAX6643/MAX

6644/MAX6645


______________________________________________________________________________________ 13

3) Route the DXP and GND traces parallel and close to

each other, away from any high-voltage traces suchas +12VDC. Avoid leakage currents from PCB conta-mination. A 20M leakage path from DXP to groundcauses approximately +1C error.

4) Route as few vias and crossunders as possible tominimize copper/solder thermocouple effects.

5) When introducing a thermocouple, make sure thatboth the DXP and the GND paths have matchingthermocouples. In general, PCB-induced thermocou-ples are not a serious problem. A copper solder ther-mocouple exhibits 3V/C, and it takesapproximately 200V of voltage error at DXP/GND tocause a +1C measurement error, so most parasiticthermocouple errors are swamped out.

6) Use wide traces. Narrow traces are more inductive

and tend to pick up radiated noise. The 10-mil widthsand spacings are recommended, but are notabsolutely necessary (as they offer only a minorimprovement in leakage and noise), but use themwhere practical.

7) Placing an electrically clean copper ground planebetween the DXP traces and traces carrying high-frequency noise signals helps reduce EMI.

Chip InformationTRANSISTOR COUNT: 12,518

PROCESS: BiCMOS


14/17

MAX6643/MAX

6644/MAX6645


14 ______________________________________________________________________________________

PART

PACKAGE-PINS

STARTUP

DELAY(s)

SP

IN-UP

TIME(s)

STARTDUTY

CYC

LE(%)

MINIM

UM

DUTY

CYC

LE(%)

CHA

NNELS

TL(C)

TH(C)

OT(C)

FULLSPD

POLARITY

FA

N_

IN1

FA

N_

IN2

MAX6643

LBFAEEQSOP-16 0.5 8 40 40

Remote,

local

15 to

55

20 to

60

60 to

100FULLSPD Tach/off Tach/off

MAX6643

LBBAEEQSOP-16 0.5 8 30 30

Remote,

local

15 to

55

20 to

60

60 to

100FULLSPD Tach/off Tach/off

MAX6644

LBAAEEQSOP-16 0.5 8 30 0

Remote,

remote

15 to

55

20 to

60

60 to

100

Locked

rotor/tach/

current

sense

Locked

rotor/tach/

current

sense

MAX6645ABFAUB

MAX-10 0.5 8 40 40 Remote,remote

45 50 75

Locked

rotor/tach/current

sense

Locked

rotor/tach/current

sense

Selector Guide

Pin Configurations

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

TH1 VDD

TH2

OT1

OT2

PWM_OUT

FAN_IN1

FAN_IN2

OT

TOP VIEW

MAX6643

QSOP

TL2

TL1

FULLSPD(FULLSPD)

FANFAIL

TACHSET

GND

DXP

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

TH1 VDD

TH2

OT1

OT2

PWM_OUT

FAN_IN1

FAN_IN2

OT

MAX6644

QSOP

TL2

TL1

DXP2

FANFAIL

TACHSET

GND

DXP1

1

2

3

4

5

10

9

8

7

6

VDD

PWM_OUT

FAN_IN1

FAN_IN2GND

DXP2

TACHSET

FANFAIL

MAX6645

MAX

OTDXP1

() ARE FOR MAX6643_A ONLY.


15/17

MAX6643/MAX

6644/MAX6645


______________________________________________________________________________________ 15

MAX6643

MAX6644

MAX6645

DXP1/(DXP)

DXP2TEMPERATURE

SENSOR

TEMPERATURE

LOGICPWM

GENERATOR

FAN-FAILDETECTION

DUTY CYCLE

ANALOG SENSE

TACHOMETER

LOCKED ROTOR IN

ANALOG SENSE

TACHOMETER

LOCKED ROTOR INOT TH TL

THRESHOLDSELECTION

FULLSPD/(FULLSPD)

PWM_OUT

FAN_IN1

FAN_IN2

FANFAILTACHSETOT1 OT2 TH1 TH2 TL1 TL2() ARE FOR MAX6643 ONLY.

Block Diagram

TO FANFAILALARM

MAX6643

TH116

15

14

13

12


(TACHOMETER MODE)


10

9

TL2

TL1

FANFAIL

TACHSET

FULLSPD

GND

DXP

VDD

VDD (+3.0V TO +5.5V)

+VFAN (5V OR 12V)

1

2

3

4

5

6

7

8

TH2

OT1

OT2

PWM_OUT

FAN_IN1

FAN_IN2

OT

4.7k

4.7k

4.7k

N

Typical Operating Circuit


16/17

MAX6643/MAX

6644/MAX6645


16 ______________________________________________________________________________________

Package Information(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline informationgo to www.maxim-ic.com/packages.)

QSOP.EPS

F1

121-0055

PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH


17/17

MAX6643/MAX

6644/MAX6645


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

2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

Package Information (continued)(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline informationgo to www.maxim-ic.com/packages.)

10LUMAX.EPS

PACKAGE OUTLINE, 10L uMAX/uSOP

1

121-0061

REV.DOCUMENT CONTROL NO.APPROVAL

PROPRIETARY INFORMATION

TITLE:

TOP VIEW

FRONT VIEW

1

0.498 REF0.0196 REFS

6

SIDE VIEW

BOTTOM VIEW

0 0 6

0.037 REF

0.0078

MAX

0.006

0.043

0.118

0.120

0.199

0.0275

0.118

0.0106

0.120

0.0197 BSC

INCHES

1

10

L1

0.0035

0.007

e

c

b

0.187

0.0157

0.114

H

L

E2

DIM

0.116

0.114

0.116

0.002

D2

E1

A1

D1

MIN

-A

0.940 REF

0.500 BSC

0.090

0.177

4.75

2.89

0.40

0.200

0.270

5.05

0.70

3.00

MILLIMETERS

0.05

2.89

2.95

2.95

-

MIN

3.00

3.05

0.15

3.05

MAX

1.10

10

0.60.1

0.60.1

0.500.1

H

4X Se

D2

D1

b

A2 A

E2

E1L

L1

c

GAGE PLANE

A2 0.030 0.037 0.75 0.95

A1

Revision History

Pages changed at Rev 2: 1, 2, 48, 1115, 17

max6643 pwm fan speed controll

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