MAXIM MAX6643, MAX6644, MAX6645 Technical data

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 and MAX6644 have nine selectable trip temperatures (in 5°C increments). The MAX6645 is factory programmed and is not pin selectable.

All versions include an overtemperature output (OT). OT can be used for warning or system shutdown. The MAX6643 also features a FULLSPD input that forces the PWM duty cycle to 100%. The MAX6643/MAX6644/ MAX6645 also feature a FANFAIL output that indicates a failed fan. See the Selector Guide for a complete list of each device’s functions.

The MAX6643 and MAX6644 are available in a small 16-pin QSOP package and the MAX6645 is available in a 10-pin µMAX®package. All versions operate from

3.0V to 5.5V supply voltages and consume 500µA (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

♦ 2°C Temperature-Measurement Accuracy ♦ FULLSPD/FULLSPD Input Sets PWM to 100% ♦ Pin-Selectable OT Output Threshold

♦ 16-Pin QSOP and 10-Pin µMAX Packages

MAX6643/MAX6644/MAX6645

Automatic PWM Fan-Speed Controllers with

Overtemperature 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 Maxim’s website at www.maxim-ic.com.

EVALUATION KIT

AVAILABLE

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

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

PART TEMP RANGE

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

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

MAX6644LBAAEE -40°C to +125°C 16 QSOP E16-1 MAX6645ABFAUB -40°C to +125°C 10 µMAX U10-2

PINPACKAGE

PKG

CODE

MAX6643/MAX6644/MAX6645

Automatic PWM Fan-Speed Controllers with Overtemperature Output

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VDD= +3.0V to +5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VDD= +3.3V, TA= +25°C.) (Note 1)

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.

VDDto 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 +(V

+ 0.3V)

FANFAIL, OT Current..........................................-1mA to +50mA

Continuous Power Dissipation (T

= +70°C)

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

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

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

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

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

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

Operating Supply Voltage Range V

Remote Temperature Error

Local Temperature Error VCC = +3.3V

Temperature Error from Supply Sensitivity

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

POR Threshold Hysteresis 90 mV

Operating Current I

Average Operating Current Duty cycle = 50%, no load 0.5 mA

Remote-Diode Sourcing Current High level 80 100 120 µA

Conversion Time 125 ms

Spin-Up Time MAX664_ _B_ _ _ _ 8 s

Startup Delay MAX664_ _B_ _ _ _ 0.5 s

Minimum Fan-Fail Tachometer Frequency

PWM_OUT Frequency F

DIGITAL OUTPUTS (OT, FANFAIL, PWM_OUT)

Output Low Voltage (OT)V

Output Low Voltage (FANFAIL, PWM_OUT)

Output-High Leakage Current I

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

= +3.3V,

PWM_OUT

+20°C ≤ T +100°C

During a conversion 0.5 1 mA

SINK

VOH = 3.3V 1 µA

= 1mA 0.4 V

= 6mA 0.5

= 1mA 0.4

TA = +20°C to +60°C ±2

≤

= 0°C to +125°C ±3

TA = +10°C to +70°C ±2.5

= 0°C to +125°C ±3.5

+3.0 +5.5 V

±0.2 °C/V

16 Hz

32 Hz

°C

MAX6643/MAX6644/MAX6645

Automatic PWM Fan-Speed Controllers with

Overtemperature Output

_______________________________________________________________________________________ 3

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS (continued)

(VDD= +3.0V to +5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VDD= +3.3V, TA= +25°C.) (Note 1)

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

DIGITAL INPUTS (FULLSPD, FULLSPD, TACHSET)

Logic-Input High V

Logic-Input Low V

Input Leakage Current VIN = GND or V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

VDD = 5.5V 3.65

VDD = 3.0V 2.2

VDD = 3.0V 0.8 V

-1 +1 µA

OPERATING SUPPLY CURRENT

vs. SUPPLY VOLTAGE

400

360

MAX6643 toc01

32.0

31.8

PWMOUT FREQUENCY

vs. DIE TEMPERATURE

MAX6643 toc02

320

280

SUPPLY CURRENT (μA)

240

200

3.0 5.5 SUPPLY VOLTAGE (V)

PWMOUT FREQUENCY

vs. SUPPLY VOLTAGE

PWMOUT FREQUENCY (Hz)

3.0 5.5 SUPPLY VOLTAGE (V)

31.6

31.4

PWMOUT FREQUENCY (Hz)

31.2

5.04.54.03.5

31.0

-40

10085603510-15

TEMPERATURE (°C)

TRIP-THRESHOLD ERROR

vs. TRIP TEMPERATURE

1.0 MAX664_L VERSIONS

MAX6643 toc03

5.04.54.03.5

0.6

0.2

-0.2

TRIP-THRESHOLD ERROR (°C)

-0.6

-1.0 20 100

TRIP TEMPERATURE (°C)

806040

MAX6643 toc04

MAX6643/MAX6644/MAX6645

Automatic PWM Fan-Speed Controllers with Overtemperature Output

4 _______________________________________________________________________________________

Pin Description

MAX6643 MAX6644 MAX6645

1, 15 1, 15 — TH1, TH2

NAME FUNCTION

High-Temperature Threshold Inputs. Connect to V leave unconnected to select the upper fan-control trip temperature (T

), in 5°C increments. See Table 1.

HIGH

, GND, or

Low-Temperature Threshold Inputs. Connect to V

2, 3 2, 3 — TL2, TL1

441FANFAIL

5 5 2 TACHSET

6 — — FULLSPD

———FULLSPD

7 7 4 GND Ground

8 — — DXP

— 6, 8 3, 5 DXP2, DXP1

996OT

10, 11 10, 11 7, 8

FAN_IN2,

FAN_IN1

leave unconnected to select the lower fan-control trip temperature (T

Fan-Fail Alarm Output. FANFAIL is an active-low, open-drain output. If the FAN_IN_ detects a fan failure, the FANFAIL output asserts low.

FAN_IN_ Control Input. TACHSET controls what type of fan-fail condition is being detected. Connect TACHSET to V 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.

C om b i ned C ur r ent S our ce and A/D P osi ti ve Inp ut for Rem ote D i od e. C onnect to anod e of r em ote d i od e- connected tem p er atur e- sensi ng tr ansi stor . C onnect to G N D i f no r em ote d i od e i s used . P l ace a 2200p F cap aci tor b etw een D X P _ and G N D for noi se fi l ter i ng .

Active-Low, Open-Drain Overtemperature Output. When OT threshold is exceeded, OT pulls low.

Fan- S ense Inp ut. FAN _IN _ can b e confi g ur ed to m oni tor ei ther a fan’ s l og i c- l evel l ocked - r otor outp ut, tachom eter outp ut, or senser esi stor w avefor m to d etect fan fai l ur e. The M AX 6643’ s FAN _IN _ i np ut can m oni tor onl y tachom eter si g nal s. The M AX 6644 and the M AX 6645 can m oni tor any one of the thr ee si g nal typ es as confi g ur ed usi ng the TAC H S E T i np ut.

), in 5°C increments. See Table 2.

LOW

, GND, or

, GND,

Detailed Description

The MAX6643/MAX6644/MAX6645 measure temperature and automatically adjust fan speed to ensure optimum cooling while minimizing acoustic noise from the fan.

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 0°C. Since the larger of the two temperatures prevails, a faulty or unconnected diode is not used for calculating fan speed or determining overtemperature faults.

PWM Output

The larger of the two measured temperatures is always used for fan control. The temperature is compared to three thresholds: the high-temperature threshold (T

HIGH

the low-temperature threshold (T

LOW

), and the overtem-

perature threshold, OT. The OT comparison is done once per second, whereas the comparisons with fan-control thresholds T

HIGH

and T

LOW

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 T

HIGH

, 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 T

LOW

, the duty cycle is decremented by

one step (1.5%). Since the T

HIGH

and T

LOW

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.

MAX6643/MAX6644/MAX6645

Automatic PWM Fan-Speed Controllers with

Overtemperature Output

_______________________________________________________________________________________ 5

Pin Description (continued)

Table 1. Setting T

HIGH

(MAX6643 and MAX6644)

High-Z = High impedance.

MAX6643 MAX6644 MAX6645

12 12 9 PWM_OUT

13, 14 13, 14 — OT2, OT1

16 16 10 V

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. 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.

Overtemperature Threshold Inputs. Connect to V leave unconnected to select the upper-limit OT fault output trip temperature, in 5°C increments. See Table 4.

Power-Supply Input. 3.3V nominal. Bypass VDD to GND with a

0.1µF capacitor.

, GND, or

TH2 TH1

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

HIGH

L SUFFIX

(°C)

HIGH

H SUFFIX

MAX6643/MAX6644/MAX6645

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, T

HIGH

is set to the temperature beyond which the fan should spin at 100%. T

LOW

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 T

HIGH

, the duty cycle remains at zero (see Figure 1). If the temperature increases above T

HIGH

, 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 T

HIGH

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 T

HIGH

For option 2 (minimum duty cycle = start duty cycle), if the measured temperature remains below T

HIGH

, the duty cycle does not increase and the fan continues to run at a slow speed. If the temperature increases above T

HIGH

, the duty cycle begins to increase, incrementing by 1.5% every 4s until the fan is spinning fast enough to reduce the temperature below T

HIGH

(see Figure 2). In both cases, if only a small amount of extra cooling is necessary to reduce the temperature below

Automatic PWM Fan-Speed Controllers with Overtemperature Output

6 _______________________________________________________________________________________

Table 2. Setting T

LOW

(MAX6643 and MAX6644)

Figure 1. Temperature-Controlled Duty-Cycle Change with Minimum Duty Cycle 30%

Figure 2. Temperature-Controlled Duty-Cycle Change with Minimum Duty Cycle 30%

High-Z = High impedance.

(°C)

TL2 TL1

0015

0 High-Z 20

0125

High-Z 0 30

High-Z High-Z 35

High-Z 1 40

1045

1 High-Z 50

1155

LOW

L SUFFIX

DUTY CYCLETEMPERATURE

SPIN-UP

STARTUP

SPIN-UP

STARTUP

MAX664_B HAS 30% PWM_OUT DUTY CYCLE DURING STARTUP.

TIME

HIGH

LOW

HIGH

LOW

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