Rainbow Electronics MAX6684 User Manual
General Description
The MAX6684 is an integrated fan-failure detector that
detects when a fan exhibits excessive underspeed or a
locked rotor. This device is especially well suited for critical systems where no fan control, or simple on/off control
is desired. The MAX6684 detects fan failure by evaluating fluctuations in current at the low side of the fan; no
tachometer signal is necessary. The output of the device,
FAIL, is an active-low, open-drain alarm. The MAX6684
can also be used to switch the fan on or off, based on
the state of a logic-level input, OFF. This device can be
used with fans rated at up to 24V and 250mA. The
MAX6684 is available in an 8-pin SO package, and is
specified for operation from -40°C to +85°C.
Applications
Desktop PCs
Notebooks
Networking Equipment
Telecommunications
Industrial Applications
Features
♦ Dedicated Fan-Failure Detector
♦ Works with Ordinary 2-Wire Fans
♦ No Fan Tachometer Output Required
♦ No Software Development Required
♦ No Analog Circuit Design Required
♦ Logic-Level Fan Driver Control
♦ Works with Fans Rated Up to 24V/250mA
MAX6684
Fan-Failure Detector with Integrated
Power Switch
________________________________________________________________ Maxim Integrated Products 1
Pin Configuration
Ordering Information
MAX6684
OFF
SENSE
V
CC
12V
PGND
GND
FC+
10kΩ
FC-
3.3V
1µF
0.1µF
0.1µF
FAIL
Typical Operating Circuit
19-2306; Rev 0; 1/02
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 TEMP RANGE PIN-PACKAGE
MAX6684ESA -40°C to +85°C 8 SO
TOP VIEW
SENSE
1
2
87PGND
OFFFAIL
MAX6684
GND
3
4
SO
V
6
5
FC+FC-
CC
MAX6684
Fan-Failure Detector with Integrated
Power Switch
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= 3.0 to 5.5V, OFF = VCC, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VCC= 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.
Note 1: Specifications to -40°C are guaranteed by design and not production tested.
Note 2: The MAX6684 is guaranteed to register a fault when the fan current fluctuates less than the minimum; it is guaranteed not to
register a fault when the fan current is above the maximum.
Voltages Referenced to GND, Unless Otherwise Noted
V
CC
........................................................................-0.3V to +6.0V
FC+, FC-.....................................................-0.3V to (VCC+ 0.3V)
OFF, FAIL ..............................................................-0.3V to +6.0V
PGND ....................................................................-0.3V to +0.3V
SENSE to PGND ..................................................-0.3V to +28.0V
SENSE Current................................................................1400mA
Continuous Power Dissipation (TA= +70°C)
8-Pin SO (derate 5.9mW/°C above +70°C)..................470mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature......................................................+150°C
Soldering Temperature (vapor phase, 60s).....................+215°C
Soldering Temperature (infrared, 15s).............................+220°C
Supply Voltage V
Supply Current I
V
CC
SENSE-to-PGND Output
Low Voltage
SENSE-to-PGND Output
On-Resistance
SENSE Leakage Current V
V
FAIL
V
FAIL
Average SENSE (Fan) Current 50 300
SENSE Current Shutdown VCC = 3V 600 1200 mA
Thermal Shutdown of SENSE 15°C hysteresis 160 °C
Fan-Current Fluctuation
Frequency
V
FAIL
Minimum Fan-Current Fluctuation
Level (Note 2)
OFF Input High Voltage V
OFF Input Low Voltage V
OFF Input Current -10 0 1 µA
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CC
CC
Shutdown Supply Current I
Output Low Voltage I
Output Leakage Current V
Output Delay After Fault t
SHDN
R
DSON
FD
IH
IL
I
= 300mA 3.4 mA
FAN
OFF = GND 10 µA
= 300mA 0.3 0.66 V
I
FAN
= 26V 1 10 µA
SENSE
= 3mA 0.8 V
FAIL
= 5.5V 0.1 1 µA
FAIL
No fault detected 25 400 Hz
No fault detected 15 35 60 mA
3.0 5.5 V
1 2.2 Ω
0.3 1 2.0 s
0.7 x
V
CC
0.3 x
V
CC
mA
P-P
V
V
MAX6684
Fan-Failure Detector with Integrated
Power Switch
_______________________________________________________________________________________ 3
Typical Operating Characteristics
(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
Pin Description
R
vs. TEMPERATURE
DSON
VCC = 3V
VCC = 5.5V
I
= 300mA
SENSE
-40 85
TEMPERATURE (°C)
603510-15
MAX6684 toc01
(Ω)
DSON
R
2.0
1.6
1.2
0.8
0.4
0
SUPPLY CURRENT vs. TEMPERATURE
300
275
250
SUPPLY CURRENT (µA)
225
200
-40 85
VCC = 5.5V
VCC = 3V
TEMPERATURE (°C)
NO LOAD
603510-15
MAX6684 toc02
500mA/div
V
I
V
FAIL
5V/div
SENSE
2V/div
SENSE
OVERCURRENT OPERATION
MAX6684 toc03
0A
0
0
20ms/div
PIN NAME FUNCTION
1 SENSE Positive Current-Sensing Terminal. Connect SENSE to low side of fan.
2 FAIL Active-Low, Open-Drain Fan-Failure Output
3 GND Ground
4 FC-
5 FC+
Connect to 0.1µF capacitor for most locked-rotor detection applications. To detect minimum speed,
select C
according to Minimum Speed and Locked-Rotor Detection.
F
Connect to 0.1µF capacitor for most locked-rotor detection applications. To detect minimum speed,
select C
according to Minimum Speed and Locked-Rotor Detection.
F
6VCCSupply Voltage Input. Bypass VCC to GND with a 1µF capacitor.
7 OFF Acti ve- Low Fan- C ontr ol Inp ut. D r i ve O FF hi g h or l eave fl oati ng to tur n fan on. D r i ve O FF l ow to tur n fan off.
8 PGND Power Ground. Connect to GND.
Loading...