MAX6670AUB50+T ,Remote Temperature Switches with Integrated Fan Controller/DriverApplications+12VNotebook and Desktop Computers250mANetwork Switches+3.3VFANPC Power SuppliesVDDDXP ..
MAX6673AXK+T ,PWM Output Temperature Sensors in SC70 PackagesApplications● Industrial and Process ControlPIN- TOPPART TEMP RANGE● HVACPACKAGE MARK● Environmenta ..
MAX6674ISA+ ,Cold-Junction-Compensated K-Thermocouple-to-Digital Converter (0°C to +128°C)Electrical Characteristics(V = +3.0V to +5.5V, T = -20°C to +85°C, unless otherwise noted. Typical ..
MAX6674ISA+T ,Cold-Junction-Compensated K-Thermocouple-to-Digital Converter (0°C to +128°C)FeaturesThe MAX6674 cold-junction-compensation thermocou-● Cold-Junction Compensationple-to-digital ..
MAX6675ISA ,Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0C to +1024C)ApplicationsPin ConfigurationIndustrialTOP VIEWAppliancesHVACGND 1 8 N.C.AutomotiveT- 2 7 SOMAX6675 ..
MAX6675ISA+T ,Cold-Junction-Compensated K-Thermocouple-to-Digital Converter (0°C to +1024°C)Electrical Characteristics(V = +3.0V to +5.5V, T = -20°C to +85°C, unless otherwise noted. Typical ..
MB3771 ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-8EDATA SHEETASSP For power supply
MB3771. ,Power Supply Monitor
MB3771P ,Power Supply MonitorFUJITSU SEMICONDUCTORDS04-27400-7EDATA SHEETASSP For power supply
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
MAX6670AUB50+T
Remote Temperature Switches with Integrated Fan Controller/Driver
General DescriptionThe MAX6668/MAX6670 remote-junction thermal
switches with an internal power transistor drive a cool-
ing fan rated for supply voltages up to +12V and
250mA. These devices measure the temperature of an
external P-N junction (typically a diode-connected tran-
sistor) and turn on the fan power switch when the
remote temperature rises above a factory-programmed
threshold. Self-contained and requiring no software
development, the MAX6668/MAX6670 are simple
“drop-in” fan-control solutions for a variety of systems.
The MAX6670 features an open-drain WARNoutput
that goes active when the remote temperature exceeds
the factory-programmed fan activation threshold by
+15°C. The MAX6670 features an open-drain OToutput
that goes active when the remote temperature exceeds
the factory-programmed threshold by +30°C. The
MAX6668/MAX6670 provide a fan-control input,
FORCEON, that allows the fan to be driven externally,
regardless of temperature.
Available temperature thresholds range from +40°C to
+75°C in 5°C increments. Hysteresis is preset to 8°C on
the MAX6668 or pin selectable to 4°C, 8°C, or 12°C
using a three-level logic input on the MAX6670.
Temperature threshold accuracy is ±1°C (typ) and
±2.2°C (max) for remote-junction temperatures from
+40°C to +75°C.
The MAX6668/MAX6670 operate from a +3V to +3.6V
power supply, and are specified over the automotive
temperature range (-40°C to +125°C). The MAX6668 is
offered in an 8-pin µMAX package and the MAX6670 is
available in a space-saving 10-pin µMAX package.
ApplicationsNotebook and Desktop Computers
Network Switches
PC Power Supplies
Laboratory Instruments
Card Racks
Temperature Alarms
Fan Controls
Features+12V, 250mA Integrated Fan DriverNo Calibration RequiredPin-Selectable 4°C, 8°C, or 12°C Hysteresis
(MAX6670)Factory-Programmed Temperature Thresholds
from +40°C to +75°COvertemperature Warning Signals110µA (typ) Supply CurrentSpace-Saving 8-Pin and 10-Pin µMAX Packages
MAX6668/MAX6670
Remote Temperature Switches with Integrated
Fan Controller/DriverDXP
GNDPGND
HYST
VDD
MAX6670
FORCEON
FANOUT
WARN
VDD
DXN
VDD
2200pF
2N3904
10kΩ
10kΩ
250mA
FAN+3.3V
VDD
+12V
ypical Application Circuit
Ordering Information19-2133; Rev 2; 11/02
Pin Configuration appears at end of data sheet.
Typical Operating Circuit appears at end of data sheet.
Ordering Information continued at end of data sheet.
PARTTEMP
RANGE
PI N -
PA C K A G EH R ESH - L D °
C )
MAX6668AUA40-40°C to +125°C8 µMAX40
MAX6668AUA45-40°C to +125°C8 µMAX45
MAX6668AUA50-40°C to +125°C8 µMAX50
MAX6668AUA60-40°C to +125°C8 µMAX60
MAX6668AUA70-40°C to +125°C8 µMAX70
MAX6668AUA75-40°C to +125°C8 µMAX75
MAX6668/MAX6670
Remote Temperature Switches with Integrated
Fan Controller/Driver
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VDD= +3V to +3.6V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VDD= +3.3V and TA= +25°C.)
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
PGND to GND.......................................................-0.3V to +0.3V
FANOUTto GND....................................................-0.3V to +15V
DXN to GND..........................................................-0.3V to +0.8V
DXP, WARN, HYST, FORCEON, OT...........-0.3V to (VDD+ 0.3V)
Current into VDD, GND, DXP, DXN, WARN, HYST,
FORCEON, OT..............................................................±20mA
Current into FANOUT, PGND........................................±300mA
Continuous Power Dissipation (TA= +70°C)
8-Pin µMAX (derate 4.1mW/°C above +70°C).............333mW
10-Pin µMAX (derate 5.6mW/°C above +70°C)...........444mW
Operating Temperature Range.........................-40°C to +125°C
Storage Temperature Range.............................-60°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s).................................+300°C
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
POWER SUPPLYPower-Supply RangeVDD33.6V
Average Supply CurrentIDD110200µA
Operating CurrentDuring sampling400650µA
Power-On Reset (POR) ThresholdPORVDD falling edge11.52.0V
POR Threshold Hysteresis50mV
TEMPERATURE SENSORTRJ = +40°C to +75°C (Note 1),
TA = 0°C to +85°C, VDD = +3.3V±1±2.2
FANOUT Temperature
Threshold AccuracyΔTTH
TRJ = +40°C to +75°C (Note 1),
TA = -40°C to +125°C, VDD = +3.3V±1±4
HYST = GND4
HYST = float8MAX6670
HYST = VDD12
FANOUT Temperature
Threshold HysteresisTHYST
MAX66688
WARN Temperature Threshold
(MAX6670 Only)Relative to FANOUT temperature threshold+15°C
OT Temperature Threshold
(MAX6670 Only)Relative to FANOUT temperature threshold+30°C
Supply Sensitivity of Temperature
Threshold11.6°C/V
Temperature Sample Frequency3.34Hz
FAN DRIVE OUTPUTFANOUT Output Voltage LowVOLISINK = 250mA0.51V
Thermal Shutdown170°C
Thermal Shutdown Hysteresis20°C
LOGIC INPUT/OUTPUTFORCEON Input High VoltageVIH0.8 x
VDDV
MAX6668/MAX6670
Remote Temperature Switches with Integrated
Fan Controller/Driver
ELECTRICAL CHARACTERISTICS (continued)(VDD= +3V to +3.6V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at VDD= +3.3V and TA= +25°C.)
Note 1:TRJis the temperature of the remote P-N junction.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSFORCEON Input Low VoltageVIL0.2 x
VDDV
FORCEON Input Bias CurrentV FORCEON = VDD or GND1µA
WARN, OT Output Voltage LowVOLISINK = 6mA0.5V
WARN, OT Output High Leakage
CurrentIOHV WARN or V OT = +5.5V1µA
Typical Operating Characteristics(TA = +25°C, unless otherwise noted.)
FANOUT CURRENT
vs. FANOUT VOLTAGE
MAX6668/70 toc01
IFANOUT (mA)
FANOUT
(V)
TA = +25°C
VDD = +3.3V
FANOUT VOLTAGE
vs. SUPPLY VOLTAGE
MAX6668/70 toc02
VDD (V)
FANOUT
(V)TA = +105°C
TA = +65°C
TA = +25°C
IFANOUT = 250mA
SUPPLY CURRENT
vs. TEMPERATURE
MAX6668/70 toc03
TEMPERATURE (°C)
IDD255075100
VDD = +3.3V, IFANOUT = 250mA
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX6668/70 toc04
VDD (V)
IDD
FORCEON = VDD
TEMPERATURE THRESHOLD ERROR
MAX6668/70 toc05
THRESHOLD ERROR (°C)
PERCENTAGE OF SAMPLES (%)
MAX6670AUB040
119 SAMPLES
MAX6668/MAX6670
Detailed DescriptionThe MAX6668/MAX6670 are simple fan controllers/dri-
vers that turn on an internal power transistor when the
sensed temperature of an external P-N junction
exceeds a factory-set threshold. By connecting a small
(up to +12V/250mA nominal) cooling fan to FANOUT, a
simple on/off fan-control system is created. Do not con-
nect the fan to a power supply of higher than 12V nomi-
nal, 15V maximum.
FANOUTDriver and FORCEONController
FANOUTFan-Driver OutputFANOUTis an open-drain output that sinks greater than
250mA of current to turn on the fan, either when the fan
trip threshold is exceeded or the fan is forced on by dri-
ving FORCEONlow.
FORCEONFan-Control Input Drive FORCEONlow to turn on the fan when the
MAX6670’s remote-sensing junction temperature is less
than the fan trip threshold temperature. This overrides
the internal control circuitry and allows for an external
device to activate the fan.
Overtemperature Alarm Outputs
WARNOutput (MAX6670 Only)WARNis an active-low, open-drain digital output that
indicates when the external P-N junction’s temperature
exceeds 15°C above the fan trip threshold. The WARN
output serves as a warning that the system temperature
has continued to rise well above the fan activation tem-
perature.
Output (MAX6670 Only)is an active-low, open-drain digital output that indi-
cates when the external P-N junction’s temperature
exceeds 30°C above the fan trip threshold. OTserves
as a thermal shutdown output to the system in case of
excessive temperature rise.
Hysteresis InputThe 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 FANOUTpin goes
active and powers the fan when the external P-N junc-
tion’s temperature exceeds the factory-programmed
Remote Temperature Switches with Integrated
Fan Controller/Driver
Pin Description
PIN
MAX6668MAX6670
NAMEFUNCTION1PGNDPower Ground. PGND is the power ground for the FANOUT power MOSFET switch.FORCEONFan-Control Input. Drive FORCEON high for normal operation. Drive FORCEON low
to force fan on.3DXP
Current Source Positive Input. Connect to the anode of the external diode-
connected transistor. Do not leave DXP floating. Connect a 2200pF capacitor
between DXP and DXN for noise filtering.4DXNCurrent Sink Negative Input. Connect to the cathode of the external diode-
connected transistor. DXN is internally biased to a diode voltage drop.
5, 77GNDGroundVDDPositive Power Supply
810FANOUT
Fan-Drive Output. FANOUT is an open-drain power MOSFET that sinks up to 250mA
current to turn on the fan when the sensed temperature exceeds the fan trip
threshold or the fan is forced on by driving FORCEON low.2WARNTemperature Warning Output. WARN is an open-drain output that goes low when
the sensed junction temperature is 15°C higher than the fan trip threshold.6OTOvertemperature Output. OT is an open-drain output that goes low when the sensed
junction temperature is 30°C higher than the fan trip threshold.9HYST
Hysteresis Control Input. HYST is a three-level logic input for controlling the fan-
drive comparator’s hysteresis. Connect HYST to GND for 4°C hysteresis, to VDD for
12°C hysteresis, or leave floating for 8°C hysteresis.
trip temperature. As the cooling fan operates, the cir-
cuit board temperature should decrease, which causes
the external P-N junction’s temperature to decrease.
When the P-N junction’s temperature is equal to the trip
threshold minus the hysteresis, the FANOUTpin turns
the fan off, removing power from the fan. For the
MAX6670, HYST is a three-level logic input for control-
ling the fan-drive comparator’s hysteresis. Connect
HYST to GND to select 4°C hysteresis, to VDDto select
12°C hysteresis, or leave floating to select 8°C hystere-
sis. The MAX6668 has a built-in hysteresis of 8°C. This
allows the amount of hysteresis to be matched to the
cooling and noise requirements of the system. Figure 1
shows the temperature trip threshold hysteresis.
Applications Information
Remote-Diode SelectionThe MAX6668/MAX6670 directly measure the die tem-
perature of CPUs and other ICs that have on-board tem-
perature-sensing diodes (see Typical OperatingCircuit)
or they can measure the temperature of a discrete
diode-connected transistor. For best accuracy, the dis-
crete transistor should be a small-signal device with its
collector and base connected together. Several satisfac-
tory discrete sensing transistors are shown in Table 1.
The sensing transistor must be a small-signal type with
a relatively high forward voltage. Otherwise, the DXP
input voltage range may be violated. The forward volt-
age at the highest expected temperature must be
greater than 0.25V at 10µA, and at the lowest expected
temperature, forward voltage must be less than 0.95V
at 100µA. Do not use large power transistors. Also,
ensure that the base resistance is less than 100Ω. Tight
specifications for forward current gain (50 < BF< 150,
for example) indicate that the manufacturer has good
process controls and that the transistors have consis-
tent VBEcharacteristics.
Noise-Filtering CapacitorIn noisy environments, high-frequency noise can be
attenuated using an external 2200pF capacitor located
at the DXP and DXN pins. Larger capacitor values may
be used for additional filtering, but do not exceed
3300pF; excessive capacitance increases error. Figure
2 shows the recommended DXP/DXN PC traces.
Bypassing and LayoutThe location of the remote-sensing junction in the sys-
tem affects the MAX6668/MAX6670s’ operation. When
using a discrete temperature-sensing transistor, place
the sensing junction close to major heat-generating
components, such as a high-speed CPU or a power
device.
To minimize noise and other errors, follow the guide-
lines below:
1) Place the MAX6668/MAX6670 as close as possible to
the remote diode. In a noisy environment, such as a
computer motherboard, this distance can be 10cm to
20cm (typ) or more as long as the worst noise
sources (such as CRTs, clock generators, memory
buses, and ISA/PCI buses) are avoided. In general,
minimize the distance to the remote-sensing junction.
2) Do not route the DXP/DXN traces next to the deflec-
tion coils of a CRT. Also, do not route the traces
across a fast memory bus, which can introduce
+30°C error or more, even with good filtering.
3) Route the DXP and DXN traces in parallel and in
close proximity to each other, away from any high-
voltage traces, such as +12VDC. Avoid leakage cur-
rents from PC board contamination, since a 20MΩ
leakage path from DXP to GND causes about +1°C
error.
4) Connect guard traces to GND on either side of the
DXP/DXN traces (Figure 2). With guard traces in
place, routing near high-voltage traces is no longer
an issue.
5) Route through as few vias and crossunders as possi-
ble to minimize copper/solder thermocouple effects.
6) Use wide traces where possible. Narrow traces are
more inductive and tend to pick up radiated noise.
7) Do not use copper as an EMI shield. Only ferrous
materials such as steel work well. Placing a copper
ground plane between the DXP/DXN traces and
other traces carrying high-frequency noise signals
does not help reduce EMI.
The MAX6668/MAX6670s’ PGND is the ground return
for the fan driver. Bypass VDDto GND with a 1µF
capacitor located as close to VDDas possible. Add
additional bypass capacitors for long VDDand GND
lines.
MAX6668/MAX6670
Remote Temperature Switches with Integrated
Fan Controller/Driver
MANUFACTURERMODEL NO.Central Semiconductor (USA)CMPT3904
ON Semiconductor (USA)2N3904, 2N3906
Rohm Semiconductor (USA)SST3904
Samsung (Korea)KST3904-TF
Siemens (Germany)SMBT3904
Zetex (England)FMMT3904CT-ND
Table 1. Remote-Sensor Transistor
Manufacturers
MAX6668/MAX6670
Chip InformationTRANSISTOR COUNT: 8113
PROCESS: BiCMOS
Remote Temperature Switches with Integrated
Fan Controller/DriverGND
DXP
DXN
GND
10MILS
10MILS
10MILS
MINIMUM
10MILS
Figure 2. Recommended DXP/DXN PC Traces
TRIP TEMPERATURE
TRIP TEMPERATURE
– HYSTERESIS
TIME
MAX6668
MAX6670
FANOUT
Figure 1. Temperature Trip Threshold Hysteresis
DXP
GNDPGND
HYST
VDD
+4.5V TO +12V
MAX6670
FORCEON
FANOUT
WARN
VDD
VDD
DXN
VDD
+3V TO +3.6V
CPU
Typical Operating CircuitVDD
GNDDXN
FANOUT
GNDFORCEON
DXP
PGND
μMAX
TOP VIEW
MAX6668
FANOUT
HYST
VDD
GNDDXN
DXP
PGND
MAX6670
μMAXFORCEON
WARN
Pin Configurations
Ordering Information
PARTTEMP
RANGE
PI N -
PA C K A G EH R ESH - L D °
C )
MAX6670AUB40-40°C to +125°C10 µMAX40
MAX6670AUB45-40°C to +125°C10 µMAX45
MAX6670AUB50-40°C to +125°C10 µMAX50
MAX6670AUB55-40°C to +125°C10 µMAX55
MAX6670AUB60-40°C to +125°C10 µMAX60
MAX6670AUB65-40°C to +125°C10 µMAX65
MAX6670AUB70-40°C to +125°C10 µMAX70
MAX6670AUB75-40°C to +125°C10 µMAX75
