Rainbow Electronics MAX6665 User Manual

Page 1

General Description

The MAX6665 is a fully integrated thermal switch with an internal power transistor for driving a cooling fan rated up to 24V and 250mA. When the MAX6665’s temperature rises above a factory-programmed threshold, the FANOUT pin becomes active and powers the fan.

The MAX6665 is available with factory-programmed fan activation threshold temperatures from +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 hysteresis is pin selectable to 1°C, 4°C, or 8°C. Two opendrain logic outputs indicate overtemperature conditions: WARN is activated when the temperature is 15°C above the fan activation threshold, and OT is activated when the temperature is 30°C above the threshold. These features can be used to safely power down systems that are overheated.

The MAX6665 operates from a +2.7V to +5.5V power supply, and the associated fan can be powered from

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

Pin Configuration

FANON

GND

HYST

+3.3V

+4.5V TO +24V

100mA TO 250mA COOLING FAN

100kΩ

1µF

MAX6665

FORCEON

FANOUT

WARN

100kΩ

Typical Operating Circuit

19-2056; Rev 0; 5/01

Ordering Information

*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.

PART

MAX6665ASA40

MAX6665ASA45

MAX6665ASA50

MAX6665ASA55

MAX6665ASA60

MAX6665ASA65

MAX6665ASA70

TEMP.

RANGE

-40°C to +125°C

PINPACKAGE

8 SO-EP* 40°C

8 SO-EP* 45°C

8 SO-EP* 50°C

8 SO-EP* 55°C

8 SO-EP* 60°C

8 SO-EP* 65°C

8 SO-EP* 70°C

THRESHOLD

TOP VIEW

GND

FORCEON

HYST

FANON

MAX6665

7 V

FANOUT

WARN

Page 2

MAX6665

Fan Controller/Driver with FactoryProgrammed 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.

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

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

FORCEON, HYST, FANON to GND............-0.3V to (V

+ 0.3V)

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

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

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

Continuous Power Dissipation (T

= +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)

Supply Voltage VDD pin 2.7 5.5 V

Supply Current No load 65 200 µA

FANOUT Drive Voltage FANOUT pin 26 V

FAN OUT Outp ut C ur rent C ap ab ility

FANOUT Leakage Current V

FANOUT Threshold, T

FANOUT Threshold Error -3 ±1+3°C

FANOUT Hysteresis

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 I

FANON Output Low Voltage I

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

Open-Drain Leakage Current V Input Low Voltage FORCEON and HYST pins 0.3V Input High Voltage FORCEON and HYST pins 0.7V

Input Current

PARAMETER CONDITIONS MIN TYP MAX UNITS

MAX6665ASA40 40

MAX6665ASA45 45

MAX6665ASA50 50

MAX6665ASA55 55

MAX6665ASA60 60

MAX6665ASA65 65

MAX6665ASA70 70

HYST is unconnected 1

HYST ≤ 0.3V

HYST ≥ 0.7V

FANON

WARN

FORCEON connected to VDD or GND -1 +1

HYST connected to V

< 0.8V 250

FANOUT

< 0.6V, TA≤ TTH +10°C, VCC≥ +3.3V 250

FANOUT

= 26V, TA = +60°C3µA

FANOUT

= 0.5mA source 2.0 V

= 0.5mA sink 0.7 V

= 1.2mA or I OT = 1.2mA sink 0.3

= 20mA or I OT = 20mA sink 0.5

= 5.5V or V OT = 5.5V 0.1 µA

WARN

or GND -15 +15

°C

µA

Page 3

MAX6665

Fan Controller/Driver with Factory-

Programmed Temperature Thresholds

_______________________________________________________________________________________ 3

Typical Operating Characteristics

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

FANOUT VOLTAGE vs. CURRENT

900

TA = +75°C

800

700

600

500

400

300

FANOUT VOLTAGE (mV)

200

100

10 100 1000

FANOUT CURRENT (mA)

NO-LOAD SUPPLY CURRENT

vs. TEMPERATURE

FORCEON = V

SUPPLY CURRENT (µA)

-40 0-20 20 40 60 80 100 120

VDD = +3.3V

TEMPERATURE (°C)

VDD = +2.7V

VDD = +3.3V

VDD = +5V

VDD = +5.0V

VDD = +2.7V

MAX6665 toc01

MAX6665 toc03

FANOUT VOLTAGE vs. SUPPLY VOLTAGE

550

FANOUT CURRENT = 250mA

500

450

400

350

FANOUT VOLTAGE (mV)

300

250

2.7 3.9 4.33.1 3.5 4.7 5.1 5.5

TA = +75°C

TA = +50°C

SUPPLY VOLTAGE (V)

TEMPERATURE THRESHOLD

DISTRIBUTION

MAX6665ASA55

100 SAMPLES

PERCENTAGE OF SAMPLES (%)

-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 ERROR (°C)

MAX6665 toc02

MAX6665 toc04

Page 4

MAX6665

Fan Controller/Driver with FactoryProgrammed Temperature Thresholds

4 _______________________________________________________________________________________

Detailed Description

The MAX6665 is a simple fan controller/driver that turns on the internal power transistor when its die temperature exceeds a factory-set threshold. By connecting a small (typically 5V to 12V, 100mA to 250mA) cooling fan to FANOUT, a simple on/off fan-control system is created. FANOUT drives the fan’s low side. The fan’s positive supply pin should be connected to its normal power-supply voltage (up to 24V nominal).

To turn the fan on when the MAX6665’s die temperature is less than the threshold voltage, drive FORCEON low. This overrides the internal control circuitry and allows an external device to activate the fan. FANON is an active-high push-pull logic output that goes high when the fan is turned on, either when temperature exceeds the threshold or the fan is forced on.

WARN is an active-low, open-drain digital output that indicates the MAX6665’s die temperature exceeds 15°C above the fan trip threshold. WARN output serves as a warning that the system temperature has continued to rise well above the fan activation temperature. OT is an active-low open-drain digital output that indicates the MAX6665’s die temperature exceeds 30°C above the fan trip threshold. It serves as a thermal shutdown output to the system in case of excessive temperature rise. Figure 1 shows a typical application circuit for a high-reliability, fail-safe temperature monitor.

Applications Information

Thermal Considerations and Hysteresis

The temperature comparator has hysteresis to prevent small temperature changes near the threshold temperature from causing the fan to turn on and off repeatedly over short periods of time. The FANOUT pin goes active and powers the fan when the MAX6665’s die temperature exceeds the factory-programmed trip temperature. As the cooling fan operates, the circuit board temperature should decrease, which in turn causes the MAX6665’s die temperature to decrease. When the die temperature is equal to the trip threshold minus the hysteresis, the FANOUT pin turns the fan off, removing power from the fan. The HYST pin sets the amount of hysteresis to 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 onchip power transistor causes the die temperature to increase. For example, assume the MAX6665 controls a 125mA fan. When the fan is operating, the voltage drop across the output transistor is typically under 250mV. At 250mV, the power dissipation is 31.25mW. The thermal resistance of the MAX6665 package (with EP soldered) is 51°C/W, so the die temperature

Pin Description

PIN NAME FUNCTION

1 GND Ground

2 FORCEON

3 HYST

4 FANON

5 OT

6 WARN

7VDDSupply Voltage. Bypass with a 1µF capacitor to GND as close to VDD pin as possible.

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

Exposed

Paddle

GND

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

Three-State Hysteresis Input. Connect HYST to V unconnected for 1°C hysteresis.

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

Overtemperature Output. Active-low when the temperature is 30°C above the fan threshold. Opendrain output, requires resistive pullup.

Overtemperature Warning Output. Active-low when the temperature is 15°C above the fan threshold. Open-drain output, requires resistive pullup.

Ground

for 8°C, GND for 4°C, and leave HYST

Page 5

increases by a maximum of:

51°C/W x 0.03125W = 1.59°C

Therefore, the effective hysteresis is about 1.59°C higher 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 selfheating, thereby increasing the effective hysteresis. When using higher-power fans, be sure that the MAX6665’s power dissipation does not cause so much self-heating that the MAX6665 stays on constantly.

Locating the MAX6665

The location of the MAX6665 in the system affects its operation. Because the fan is turned on and off based on the MAX6665’s die temperature, place the MAX6665 close to major heat-generating components in the system—a high-speed CPU or a power device, for example. A higher supply voltage reduces the FANOUT voltage, which reduces the self-heating effects.

The die temperature of the MAX6665 tracks the temperature of its leads and the EP. If it is soldered to a PC board, it quickly reaches the temperature of the traces in that section of the circuit board. Air temperature affects the die temperature. Since the plastic package does not conduct heat as well as the leads, the effect of air temperature is much less than that of lead temperature.

Layout Issues

The MAX6665’s GND pin is ground return for the fan driver and the device. Large fan current induces noise (ground bounce) to the MAX6665. Bypass VDDto GND with a 1µF tantalum capacitor located as close to the MAX6665 as possible. For long VDDand GND lines, an additional bypass capacitor may be needed. The bypass capacitor reduces GND noise. The EP is internally connected to the GND pin. Solder the EP to the ground plane for better electrical and thermal performance.

MAX6665

Fan Controller/Driver with Factory-

Programmed Temperature Thresholds

_______________________________________________________________________________________ 5

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

+4.5V TO +24V

100mA TO 250mA COOLING FAN

+3.3V

1µF

HYST

FORCEON

MAX6665

GND

FANOUT

WARN

FANON

100kΩ

SYSTEM POWER SHUTDOWN

µP

I/O

Page 6

MAX6665

Fan Controller/Driver with FactoryProgrammed 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

Package Information

Chip Information

TRANSISTOR COUNT: 1543 MOS

119 BIPOLAR

PROCESS: BiCMOS

8L, SOIC EXP. PAD.EPS