MAX6684ESA+ Fast Delivery |IC PHOENIX CO.,LIMITED

MAX6684ESA+ ,Fan-Failure Detector with Integrated Power SwitchELECTRICAL CHARACTERISTICS(V = 3.0 to 5.5V, OFF = V , T = -40°C to +85°C, unless otherwise noted. T ..
MAX6689UP9A+ ,7-Channel Precision Temperature MonitorApplicationsMAX6689EP9E+ 20 QSOP 1001 111 E20-1Desktop Computers MAX6689UP34+ 20 TSSOP 0011 010 U20 ..
MAX6689UP9A+T ,7-Channel Precision Temperature MonitorELECTRICAL CHARACTERISTICS(V = +3.0V to +5.5V, V = V , T = -40°C to +125°C, unless otherwise noted. ..
MAX668EUB ,1.8V to 28V Input / PWM Step-Up Controllers in MAXELECTRICAL CHARACTERISTICS(V = LDO = +5V, R = 200kΩ, T = 0°C to +85°C, unless otherwise noted. Typi ..
MAX668EUB ,1.8V to 28V Input / PWM Step-Up Controllers in MAXFeaturesThe MAX668/MAX669 constant-frequency, pulse-width-' 1.8V Minimum Start-Up Voltage (MAX669)m ..
MAX668EUB ,1.8V to 28V Input / PWM Step-Up Controllers in MAXApplicationsoperates in PWM mode at medium and heavy loads forlowest noise and optimum efficiency, ..
MB3771PF ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
MB3771PF. ,Power Supply MonitorapplicationsBIPOLARPower Supply MonitorMB3771nnnn DESCRIPTIONThe Fujitsu MB3771 is designed to moni ..
MB3771PF-G-BND-JNE1 , ASSP For power supply applications BIPOLAR Power Supply Monitor
MB3771PS ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
MB3771PS ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
MB3773 ,Power Supply Monitor with Watch-Dog TimerFUJITSU SEMICONDUCTORDS04-27401-4EDATA SHEETASSPPower Supply Monitor with Watch-Dog TimerMB3773n DE ..

MAX6684ESA+
Fan-Failure Detector with Integrated Power Switch
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 criti-
cal systems where no fan control, or simple on/off control
is desired. The MAX6684 detects fan failure by evaluat-
ing 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
FeaturesDedicated Fan-Failure DetectorWorks with Ordinary 2-Wire FansNo Fan Tachometer Output RequiredNo Software Development RequiredNo Analog Circuit Design RequiredLogic-Level Fan Driver ControlWorks with Fans Rated Up to 24V/250mA
MAX6684
Fan-Failure Detector with Integrated
Power Switch
VCC
FC+FC-
PGND
OFFFAIL
GND
SENSE
TOP VIEW
MAX6684
Pin Configuration
Ordering Information
MAX6684
OFF
SENSE
VCC
12V
PGNDGND
FC+
10kΩ
FC-
3.3V
1μF
0.1μF
0.1μF
FAIL
Typical Operating Circuit
19-2306; Rev 0; 1/02
PARTTEMP RANGEPIN-PACKAGE
MAX6684ESA-40°C to +85°C8 SO
MAX6684
Fan-Failure Detector with Integrated
Power Switch
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
VCC........................................................................-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
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Supply VoltageVCC3.05.5V
Supply CurrentICCIFAN = 300mA3.4mA
VCC Shutdown Supply CurrentISHDNOFF = GND10µA
SENSE-to-PGND Output
Low VoltageIFAN = 300mA0.30.66V
SENSE-to-PGND Output
On-ResistanceRDSON12.2Ω
SENSE Leakage CurrentVSENSE = 26V110µA
V FAIL Output Low VoltageI FAIL = 3mA0.8V
V FAIL Output Leakage CurrentV FAIL = 5.5V0.11µA
Average SENSE (Fan) Current50300mA
SENSE Current ShutdownVCC = 3V6001200mA
Thermal Shutdown of SENSE15°C hysteresis160°C
Fan-Current Fluctuation
FrequencyNo fault detected25400Hz
V FAIL Output Delay After FaulttFD0.312.0s
Minimum Fan-Current Fluctuation
Level (Note 2)No fault detected153560mAP-P
OFF Input High VoltageVIH0.7 x
VCCV
OFF Input Low VoltageVIL0.3 x
VCCV
OFF Input Current-1001µA
MAX6684
Fan-Failure Detector with Integrated
Power Switch
RDSON vs. TEMPERATURE
MAX6684 toc01
TEMPERATURE (°C)
DSON 3510-15
VCC = 3V
ISENSE = 300mA
VCC = 5.5V
SUPPLY CURRENT vs. TEMPERATURE
MAX6684 toc02
TEMPERATURE (°C)
SUPPLY CURRENT (3510-15
VCC = 3V
NO LOAD
VCC = 5.5V
OVERCURRENT OPERATION
MAX6684 toc03
20ms/div
ISENSE
500mA/div
VFAIL
5V/div
VSENSE
2V/div
Typical Operating Characteristics
(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
Pin Description
PINNAMEFUNCTIONSENSEPositive Current-Sensing Terminal. Connect SENSE to low side of fan.FAILActive-Low, Open-Drain Fan-Failure OutputGNDGroundFC-Connect to 0.1µF capacitor for most locked-rotor detection applications. To detect minimum speed,
select CF according to Minimum Speed and Locked-Rotor Detection.FC+Connect to 0.1μF capacitor for most locked-rotor detection applications. To detect minimum speed,
select CF according to Minimum Speed and Locked-Rotor Detection.
6VCCSupply Voltage Input. Bypass VCC to GND with a 1µF capacitor.OFFActi 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.PGNDPower Ground. Connect to GND.
MAX6684
Detailed Description
The MAX6684 detects fan failure in brushless DC fans.
This device is especially well suited for critical systems
where no fan control is desired. No software is neces-
sary to control the MAX6684.
Fan-Failure Detection
Fan failure is determined based on the fan current
observed at SENSE. The current observed at SENSE is
converted to a voltage, VFAN, and highpass filtered by
the capacitor, CF, from FC+ to FC- (Figure 1).
Fan-Failure Detector with Integrated
Power Switch
FC-BLANK
NOISESQ
CURRENT-SENSE AND
CURRENT-LIMITING
CIRCUIT OFF
FC+
LATCH
COMP
8.2kHz 8Hz
OSCILLATORFAULT-
DETECTION
DELAY
VCC
SENSE
GNDPGND
FAIL
VFAN
70mVCF
MAX6684
Figure 1. MAX6684 Functional Diagram
NORMAL
FAN OPERATION
UNDERCURRENT*
UNDERCURRENT*
NORMAL
CURRENT
OVERCURRENTNO THERMAL
SHUTDOWN
THERMAL
SHUTDOWN
OVERCURRENT
OVERCURRENT
OVERCURRENTOVERCURRENT
*INVALID COMMUTATION CURRENT
NOTE: A THERMAL SHUTDOWN CONDITION OVERIDES ALL OTHER CONDITIONS,
IMMEDIATELY SHUTTING THE FAN OFF AND SIGNALING FAIL.
THERMAL SHUTDOWNTHERMAL SHUTDOWN
NORMAL
CURRENT
FAN ON,
FAIL HIGH
2ms DELAY
FAN ON,
FAIL LOW
FAN OFF,
FAIL LOW
2ms DELAY
1s DELAY60ms DELAY
NORMAL
CURRENT
Figure 2. MAX6684 State Diagram
Undercurrent (AC Component)
Fan failure is signaled if the AC component of IFANis
less than 35mAP-Pand remains out of specification for
at least 1s (Figure 2). The fan remains powered during
undercurrent failures.
Minimum Speed and
Locked-Rotor Detection
The MAX6684 asserts FAILif the fan-current fluctuation
frequency is below 25Hz, which corresponds to a fan
speed of approximately 700rpm. The fan remains pow-
ered during a locked rotor or an under-speed failure
condition (Figures 3 and 4).
The MAX6684 can be designed to detect fan failure
below intended speeds by varying the value of CF.
Because of the complexity of fan-current waveforms,
the value of CFhas to be arrived at empirically and
must be verified by bench testing. The guidelines of
Figure 5are only appropriate for the test signals used
and do not represent all possible fan waveforms. They
are to illustrate the ability of the MAX6684 to discrimi-
nate failure due to low fan speed. As a rule, failure typi-
cally occurs when the amplitude measured at pin 4 of
the MAX6684 drops below 70mV.
Overcurrent Protection
If an overcurrent condition begins and continues for 2ms,
fan failure is signaled for 60ms. During this 60ms period,
the power to the fan is turned off. If the part does not enter
thermal shutdown and the overcurrent condition contin-
ues, power to the fan is turned on every 62ms for 2ms
(see Overcurrent Operation in Typical OperatingChar-
acteristics). Once the overcurrent condition is removed,
the fan is powered continuously. A 0.1µF capacitor
between SENSE and PGND prevents the internal DMOS
switch from being damaged by back EMF current.
Thermal Shutdown
A die temperature in excess of +160°C initiates thermal
shutdown. In thermal shutdown, the MAX6684 shuts off
the fan and the FAILoutput asserts. While in thermal
shutdown, the MAX6684 monitors the die temperature.
Once the die has cooled to below +145°C, the MAX6684
exits thermal shutdown and power is returned to the fan.
A thermal shutdown fault condition has precedence over
all other failure modes. While the MAX6684 die is over
temperature, power is not cycled to the fan, as occurs
during overcurrent failure.
MAX6684
Fan-Failure Detector with Integrated
Power Switch
Figure 3. MAX6684 Commutation Fault Timing Diagram
FAIL
100Hz
tFD
Figure 4. Current Fluctuation and Commutation Frequency
Diagram
FAIL HIGH
FAIL LOW 100200300400
CURRENT FLUCTUATION
vs. COMMUTATION FREQUENCY
CURRENT COMMUTATION FREQUENCY (Hz)
CURRENT FLUCTUATION
(AC COMPONENT) (mA
P-P
MAX6684
OFF
SENSE
APPROXIMATE FAILURE FREQUENCIES:
VCC
FUNCTION
GENERATOR*
*35mAP-P SINE-WAVE AC COMPONENT
50mA TO 300mA DC COMPONENT
PGNDGND
FC+
CF = 0.033μF < 25Hz
CF = 0.01μF < 86Hz
CF = 0.003μF < 250Hz
10kΩ
FC-
3.3V
FAIL
CF
Figure 5. Test Circuit Demonstrates Failure Frequency as a
Function of the Value of CF
MAX6684
FAILOutput
The FAILoutput is an active-low, open-drain alarm.
Three fan-failure modes are possible (see the Fan-
Failure Detectionsection).
OFF
Drive OFFlow to turn off power to the fan. If OFFis tied
high or floating, the MAX6684 is enabled.
Applications Information
Fan Compatibility
This device can be used with fans that require operat-
ing voltages up to 24V and supply currents up to
250mA. See the Fan-Failure Detectionsection regard-
ing fan-current waveform issues.
Figures 6 and 7show two ways to increase the current
capability of the MAX6684. InFigure 6, a parallel exter-
nal resistance between SENSE and PGND is used to
increase current capability. This method eliminates the
fan-control functionality normally associated with the
MAX6684 OFFpin. Select the external resistor, R1,
such that approximately 100mA flows across the inter-
nal RDSONof the MAX6684, which is typically 1Ω.
Figure 7also shows how to use an external current-
boost PNP bipolar transistor to increase the current
capability of the MAX6684. This method preserves the
fan-control functionality of the OFFpin. A 6ΩRBOOST
allows approximately 100mA of the fan current to flow
through the MAX6684.
The MAX6684 is not compatible with fans designed for
use with external PWM fan controllers.
Fan-Specific Concerns
Because fan-current waveforms can vary substantially
from one given fan make or model to another, validate
the performance of the MAX6684 with the intended fan.
It is possible to encounter fans where the MAX6684 is
limited to detecting locked-rotor conditions only,
because of the nature of the fan-current waveform. In
cases where fan-speed detection does not seem to be
working properly (although locked-rotor detection is tak-
ing place), adding a 100µF capacitor across the fan
may solve the problem.
When the MAX6684 is used with fans that include
locked-rotor protection, the FAILoutput is active when
the rotor locks, and toggles each time the locked-rotor
protection built into the fan attempts a restart, over a
timeframe typically measured in seconds. Toggling
should be considered an indication of fan failure; con-
versely, a fan is functioning properly only when FAILis
constantly inactive.
Capacitor Selection
A ceramic or mylar capacitor, CF, is required from FC-
to FC+. The capacitor blocks the DC component of the
signal, allowing the MAX6684 to monitor the AC current
consumption of the fan. See the Minimum Speed and
Locked-Rotor Detectionsection for more information.
Power Supply and Bypassing
The effects of noise can be minimized by placing a 1µF
ceramic bypass capacitor close to the device’s supply pin.
Fan-Failure Detector with Integrated
Power Switch
Figure 6. Increased Current Capability Using External
Resistance
MAX6684
OFF
SENSE
VCC
PGNDGND
FC+
10kΩ
FC-
3.3V
FAIL
12V
Figure 7. Increased Current Capability Using PNP Transistor
MAX6684
OFF
SENSE
VCC
PGNDGND
FC+
10kΩ
RBOOST
FC-
3.3V
FAIL
12V

Partno	Mfg	Dc	Qty	Available	Descript
MAX6684ESA+ \|MAX6684ESA	MAXIM	N/a	1784	avai	Fan-Failure Detector with Integrated Power Switch