MAX6665ASA70+ - Maxim Integrated Products, Inc.

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 tem-

perature rises above a factory-programmed threshold,

the FANOUT pin becomes active and powers the fan.

The MAX6665 is available with factory-programmed fan

activation threshold temperatures from +40°C to +70°C

in 5°C increments. Accuracy of the fan activation trip

point is ±1°C (typ) and ±3°C (max). The trip point’s hys-

teresis is pin selectable to 1°C, 4°C, or 8°C. Two open-

drain logic outputs indicate overtemperature con-

ditions: WARN is activated when the temperature is

15°C above the fan activation threshold, and OT is acti-

vated when the temperature is 30°C above the thresh-

old. These features can be used to safely power down

systems that are overheated.

The MAX6665 operates from a +2.7V to +5.5V power

supply, and the associated fan can be powered from

4.5V to 24V. It is available in an 8-pin SO package and

operates from -40°C to +125°C.

Applications

Notebook and Desktop Computers

Servers

PC Power Supplies

Laboratory Instruments

Card Racks

Features

♦On-Chip 250mA Fan Switch

♦No External Components Required

♦Factory-Programmed Thresholds

♦Two Overtemperature Warning Signals

♦Pin-Selectable 1°C, 4°C, and 8°C Hysteresis

♦Low 65µA Supply Current

MAX6665

Fan Controller/Driver with Factory-

Programmed Temperature Thresholds

________________________________________________________________ Maxim Integrated Products 1

FANON

7VDD

HYST

GND

TOP VIEW

MAX6665

FORCEON

FANOUT

WARN

Pin Configuration

VDD

FANON

GND

HYST

VDD

+3.3V

+4.5V TO +24V

100mA TO 250mA

COOLING FAN

100kΩ

1µF

MAX6665

FORCEON

FANOUT

WARN

VDD

100kΩ

Typical Operating Circuit

19-2056; Rev 0; 5/01

Ordering Information

PART TEMP.

RANGE

PIN-

PACKAGE THRESHOLD

MAX6665ASA40 -40°C to

+125°C8 SO-EP* 40°C

MAX6665ASA45 -40°C to

+125°C8 SO-EP* 45°C

MAX6665ASA50 -40°C to

+125°C8 SO-EP* 50°C

MAX6665ASA55 -40°C to

+125°C8 SO-EP* 55°C

MAX6665ASA60 -40°C to

+125°C8 SO-EP* 60°C

MAX6665ASA65 -40°C to

+125°C8 SO-EP* 65°C

MAX6665ASA70 -40°C to

+125°C8 SO-EP* 70°C

*Exposed paddle

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

MAX6665

Fan Controller/Driver with Factory-

Programmed Temperature Thresholds

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

Note 1: Specifications over temperature are guaranteed by design. Parts are 100% production tested at 10°C below the tempera-

ture threshold.

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

FANOUT to GND ....................................................-0.3V to +28V

FORCEON, HYST, FANON to GND............-0.3V to (VDD + 0.3V)

WARN, OT to GND ...................................................-0.3V to +6V

FANOUT Continuous Current............................................400mA

All Other Pins ....................................................................±20mA

Continuous Power Dissipation (TA = +70°C)

8-Pin SO (derate 19.6mW/°C above +70°C).............1568mW

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

Junction (storage) Temperature Range ............-65°C to +150°C

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

ELECTRICAL CHARACTERISTICS

(VDD = +2.7V to +5.5V, TA= -40°C to +125°C. Typical values are at VDD = +3.3V and TA= +25°C, unless otherwise noted.) (Note 1)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Supply Voltage VDD pin 2.7 5.5 V

Supply Current No load 65 200 µA

FANOUT Drive Voltage FANOUT pin 26 V

FANOUT < 0.8V 250

FAN OUT Outp ut C ur r ent C ap ab i l i ty V

FANOUT < 0.6V, TA ≤ TTH +10°C, VCC ≥ +3.3V 250 mA

FANOUT Leakage Current V

FANOUT = 26V, TA = +60°C3µA

MAX6665ASA40 40

MAX6665ASA45 45

MAX6665ASA50 50

MAX6665ASA55 55

MAX6665ASA60 60

MAX6665ASA65 65

FANOUT Threshold, TTH

MAX6665ASA70 70

°C

FANOUT Threshold Error -3 ±1+3°C

HYST is unconnected 1

HYST ≤ 0.3VDD 4

FANOUT Hysteresis

HYST ≥ 0.7VDD 8

°C

WARN Threshold Relative to FANOUT temperature threshold +15 °C

OT Threshold Relative to FANOUT temperature threshold +30 °C

WARN and OT Hysteresis 2°C

FANON Output High Voltage IFANON = 0.5mA source 2.0 V

FANON Output Low Voltage IFANON = 0.5mA sink 0.7 V

WARN = 1.2mA or I

OT = 1.2mA sink 0.3

W ARN and O T Outp ut V ol tag e Low I

WARN = 20mA or I

OT = 20mA sink 0.5 V

Open-Drain Leakage Current V

WARN = 5.5V or V

OT = 5.5V 0.1 µA

Input Low Voltage FORCEON and HYST pins 0.3VDD V

Input High Voltage FORCEON and HYST pins 0.7VDD V

FORCEON connected to VDD or GND -1 +1

Input Current HYST connected to VDD or GND -15 +15 µA

MAX6665

Fan Controller/Driver with Factory-

Programmed Temperature Thresholds

_______________________________________________________________________________________ 3

900

800

700

600

500

400

300

200

100

10 100 1000

MAX6665 toc01

FANOUT VOLTAGE vs. CURRENT

FANOUT CURRENT (mA)

FANOUT VOLTAGE (mV)

TA = +75°C

VDD = +2.7V

VDD = +3.3V

VDD = +5.0V

250

350

300

450

400

500

550

2.7 3.9 4.33.1 3.5 4.7 5.1 5.5

MAX6665 toc02

SUPPLY VOLTAGE (V)

FANOUT VOLTAGE (mV)

FANOUT VOLTAGE vs. SUPPLY VOLTAGE

FANOUT CURRENT = 250mA

TA = +75°C

TA = +50°C

-40 0-20 20 40 60 80 100 120

NO-LOAD SUPPLY CURRENT

vs. TEMPERATURE

MAX6665 toc03

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

FORCEON = VDD VDD = +5V

VDD = +3.3V

VDD = +2.7V

-2.0 -0.5-1.5 0.5-1.0 1.0 1.5 2.0 2.5-2.5 3.0-3.0

TEMPERATURE THRESHOLD

DISTRIBUTION

MAX6665 toc04

TEMPERATURE ERROR (°C)

PERCENTAGE OF SAMPLES (%)

MAX6665ASA55

100 SAMPLES

Typical Operating Characteristics

(VDD = +3.3V, unless otherwise noted.)

MAX6665

Fan Controller/Driver with Factory-

Programmed Temperature Thresholds

4 _______________________________________________________________________________________

Detailed Description

The MAX6665 is a simple fan controller/driver that turns

on the internal power transistor when its die tempera-

ture exceeds a factory-set threshold. By connecting a

small (typically 5V to 12V, 100mA to 250mA) cooling

fan to FANOUT, a simple on/off fan-control system is

created. FANOUT drives the fan’s low side. The fan’s

positive supply pin should be connected to its normal

power-supply voltage (up to 24V nominal).

To turn the fan on when the MAX6665’s die temperature

is less than the threshold voltage, drive FORCEON low.

This overrides the internal control circuitry and allows

an external device to activate the fan. FANON is an

active-high push-pull logic output that goes high when

the fan is turned on, either when temperature exceeds

the threshold or the fan is forced on.

WARN is an active-low, open-drain digital output that

indicates the MAX6665’s die temperature exceeds

15°C above the fan trip threshold. WARN output serves

as a warning that the system temperature has contin-

ued to rise well above the fan activation temperature.

OT is an active-low open-drain digital output that indi-

cates the MAX6665’s die temperature exceeds 30°C

above the fan trip threshold. It serves as a thermal shut-

down output to the system in case of excessive temper-

ature rise. Figure 1 shows a typical application circuit

for a high-reliability, fail-safe temperature monitor.

Applications Information

Thermal Considerations and Hysteresis

The temperature comparator has hysteresis to prevent

small temperature changes near the threshold temper-

ature 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 tem-

perature. As the cooling fan operates, the circuit board

temperature should decrease, which in turn causes the

MAX6665’s die temperature to decrease. When the die

temperature is equal to the trip threshold minus the

hysteresis, the FANOUT pin turns the fan off, removing

power from the fan. The HYST pin sets the amount of

hysteresis to 1°C, 4°C, or 8°C by letting the pin float or

connecting to GND or VDD, respectively. This allows

the amount of hysteresis to be matched to the cooling

and noise requirements of the system.

Hysteresis is also affected by self-heating of the

MAX6665’s die. The fan current flowing through the on-

chip power transistor causes the die temperature to

increase. For example, assume the MAX6665 controls

a 125mA fan. When the fan is operating, the voltage

drop across the output transistor is typically under

250mV. At 250mV, the power dissipation is 31.25mW.

The thermal resistance of the MAX6665 package (with

EP soldered) is 51°C/W, so the die temperature

PIN NAME FUNCTION

1 GND Ground

2FORCEON Force Fan On Input. Set FORCEON low to force the fan switch on. Set FORCEON high for normal

operation.

3 HYST Three-State Hysteresis Input. Connect HYST to VDD for 8°C, GND for 4°C, and leave HYST

unconnected for 1°C hysteresis.

4 FANON Fan-On Indicator Output. Push-pull output. FANON is high when the fan switch is on. FANON is low

when the fan switch is off.

5OT Overtemperature Output. Active-low when the temperature is 30°C above the fan threshold. Open-

drain output, requires resistive pullup.

6WARN Overtemperature Warning Output. Active-low when the temperature is 15°C above the fan

threshold. Open-drain output, requires resistive pullup.

DD Supply Voltage. Bypass with a 1µF capacitor to GND as close to VDD pin as possible.

8FANOUT Fan-Switch (Driver) Output. Connect to the low side of a fan.

Exposed

Paddle GND Ground

Pin Description

increases by a maximum of:

51°C/W x 0.03125W = 1.59°C

Therefore, the effective hysteresis is about 1.59°C high-

er than the hysteresis selected by the HYST pin. For

example, setting the HYST pin for 8°C of hysteresis

results in an effective hysteresis of about 9.6°C.

A larger fan with a power-supply current of 250mA

causes a maximum voltage drop of 0.6V at the output

pin. This results in 150mW power dissipation and the

die temperature increases by:

51°C/W x 0.150W = 7.65°C

If the HYST pin has been set for 8°C of hysteresis, the

total effective hysteresis will be about 15.7°C.

Using fans with somewhat higher operating current

than 250mA results in higher voltage across the output

transistor. The increased power dissipation caused by

the higher current and voltage levels will increase self-

heating, 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 sys-

tem—a high-speed CPU or a power device, for exam-

ple. A higher supply voltage reduces the FANOUT

voltage, which reduces the self-heating effects.

The die temperature of the MAX6665 tracks the tempera-

ture 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 dri-

ver and the device. Large fan current induces noise

(ground bounce) to the MAX6665. Bypass VDD to GND

with a 1µF tantalum capacitor located as close to the

MAX6665 as possible. For long VDD and GND lines, an

additional bypass capacitor may be needed. The bypass

capacitor reduces GND noise. The EP is internally con-

nected to the GND pin. Solder the EP to the ground plane

for better electrical and thermal performance.

MAX6665

Fan Controller/Driver with Factory-

Programmed Temperature Thresholds

_______________________________________________________________________________________ 5

Figure 1. High-Reliability, Fail-Safe Fan Controller and Temperature Monitor

VDD

FANON

GND

HYST

VDD

+3.3V

+4.5V TO +24V

100mA TO 250mA

COOLING FAN

100kΩ

1µF

µP

I/O

SYSTEM POWER

SHUTDOWN

MAX6665

FORCEON

FANOUT

WARN

VDD

100kΩ

MAX6665

Fan Controller/Driver with Factory-

Programmed Temperature Thresholds

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

6_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

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

Package Information

8L, SOIC EXP. PAD.EPS

Chip Information

TRANSISTOR COUNT: 1543 MOS

119 BIPOLAR

PROCESS: BiCMOS