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19-2133; Rev 2; 11/02
Remote Temperature Switches with Integrated Fan Controller/Driver
General Description
The MAX6668/MAX6670 remote-junction thermal switches with an internal power transistor drive a cooling 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 transistor) 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 WARN output that goes active when the remote temperature exceeds the factory-programmed fan activation threshold by +15C. The MAX6670 features an open-drain OT output that goes active when the remote temperature exceeds the factory-programmed threshold by +30C. 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 +40C to +75C in 5C increments. Hysteresis is preset to 8C on the MAX6668 or pin selectable to 4C, 8C, or 12C using a three-level logic input on the MAX6670. Temperature threshold accuracy is 1C (typ) and 2.2C (max) for remote-junction temperatures from +40C to +75C. The MAX6668/MAX6670 operate from a +3V to +3.6V power supply, and are specified over the automotive temperature range (-40C to +125C). The MAX6668 is offered in an 8-pin MAX package and the MAX6670 is available in a space-saving 10-pin MAX package. o +12V, 250mA Integrated Fan Driver o No Calibration Required o Pin-Selectable 4C, 8C, or 12C Hysteresis (MAX6670) o Factory-Programmed Temperature Thresholds from +40C to +75C o Overtemperature Warning Signals o 110A (typ) Supply Current o Space-Saving 8-Pin and 10-Pin MAX Packages
Features
MAX6668/MAX6670
Ordering Information
PART TEMP RANGE PI NPA CK AG E 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX 8 MAX THRESHOLD ( C) 40 45 50 60 70 75
MAX6668AUA40 -40C to +125C MAX6668AUA45 -40C to +125C MAX6668AUA50 -40C to +125C MAX6668AUA60 -40C to +125C MAX6668AUA70 -40C to +125C MAX6668AUA75 -40C to +125C
Ordering Information continued at end of data sheet.
Typical Application Circuit
+12V 250mA FAN FANOUT VDD 10k
Applications
Notebook and Desktop Computers Network Switches PC Power Supplies Laboratory Instruments Card Racks Temperature Alarms Fan Controls
2N3904 CS 2200pF DXN DXP +3.3V VDD
MAX6670
WARN
VDD 10k
HYST GND
OT PGND FORCEON VDD
Pin Configuration appears at end of data sheet. Typical Operating Circuit appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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Remote Temperature Switches with Integrated Fan Controller/Driver MAX6668/MAX6670
ABSOLUTE MAXIMUM RATINGS
VDD to GND ..............................................................-0.3V to +6V PGND to GND .......................................................-0.3V to +0.3V FANOUT to 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 = +70C) 8-Pin MAX (derate 4.1mW/C above +70C) .............333mW 10-Pin MAX (derate 5.6mW/C above +70C) ...........444mW Operating Temperature Range .........................-40C to +125C Storage Temperature Range .............................-60C to +150C Junction Temperature ......................................................+150C Lead Temperature (soldering, 10s) .................................+300C
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.
ELECTRICAL CHARACTERISTICS
(VDD = +3V to +3.6V, TA = -40C to +125C, unless otherwise noted. Typical values are at VDD = +3.3V and TA = +25C.)
PARAMETER POWER SUPPLY Power-Supply Range Average Supply Current Operating Current Power-On Reset (POR) Threshold POR Threshold Hysteresis TEMPERATURE SENSOR FANOUT Temperature Threshold Accuracy TRJ = +40C to +75C (Note 1), TA = 0C to +85C, VDD = +3.3V TRJ = +40C to +75C (Note 1), TA = -40C to +125C, VDD = +3.3V HYST = GND FANOUT Temperature Threshold Hysteresis WARN Temperature Threshold (MAX6670 Only) OT Temperature Threshold (MAX6670 Only) Supply Sensitivity of Temperature Threshold Temperature Sample Frequency FAN DRIVE OUTPUT FANOUT Output Voltage Low Thermal Shutdown Thermal Shutdown Hysteresis LOGIC INPUT/OUTPUT FORCEON Input High Voltage VIH 0.8 x VDD V VOL ISINK = 250mA 0.5 170 20 1 V C C 3.3 THYST MAX6670 MAX6668 Relative to FANOUT temperature threshold Relative to FANOUT temperature threshold HYST = float HYST = VDD 1 1 4 8 12 8 +15 +30 1 4 1.6 C C C/V Hz C 2.2 C 4 POR VDD IDD During sampling VDD falling edge 1 3 110 400 1.5 50 3.6 200 650 2.0 V A A V mV SYMBOL CONDITIONS MIN TYP MAX UNITS
TTH
2
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Remote Temperature Switches with Integrated Fan Controller/Driver
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +3V to +3.6V, TA = -40C to +125C, unless otherwise noted. Typical values are at VDD = +3.3V and TA = +25C.)
PARAMETER FORCEON Input Low Voltage FORCEON Input Bias Current WARN, OT Output Voltage Low WARN, OT Output High Leakage Current VOL IOH SYMBOL VIL V FORCEON = VDD or GND ISINK = 6mA V WARN or V OT = +5.5V CONDITIONS MIN TYP MAX 0.2 x VDD 1 0.5 1 UNITS V A V A
MAX6668/MAX6670
Note 1: TRJ is the temperature of the remote P-N junction.
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
FANOUT CURRENT vs. FANOUT VOLTAGE
MAX6668/70 toc01
FANOUT VOLTAGE vs. SUPPLY VOLTAGE
MAX6668/70 toc02
SUPPLY CURRENT vs. TEMPERATURE
VDD = +3.3V, IFANOUT = 250mA 120 100
MAX6668/70 toc03
0.7 TA = +25C 0.6 0.5 VFANOUT (V) 0.4 0.3 0.2 0.1 0 0 50 100 150 200 250 VDD = +3.3V
2.0 1.8 1.6 1.4 VFANOUT (V) TA = +105C TA = +65C IFANOUT = 250mA
140
IDD (A)
1.2 1.0 0.8 0.6 0.4 0.2 0
80 60 40
TA = +25C 2.0 2.5 3.0 VDD (V) 3.5
20 0 0 25 50 75 TEMPERATURE (C) 100
300
IFANOUT (mA)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6668/70 toc04
TEMPERATURE THRESHOLD ERROR
MAX6670AUB040 119 SAMPLES
MAX6668/70 toc05
140 120 100 IDD (A) 80 60 40 20 FORCEON = VDD 0 3.0 3.3 VDD (V)
30 PERCENTAGE OF SAMPLES (%) 25 20 15 10 5
3.6
0 -1.00 -0.75 -0.50 -0.25
0
0.25 0.50 0.75
1.00
THRESHOLD ERROR (C)
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Remote Temperature Switches with Integrated Fan Controller/Driver MAX6668/MAX6670
Pin Description
PIN MAX6668 1 2 MAX6670 1 5 PGND FORCEON Power Ground. PGND is the power ground for the FANOUT power MOSFET switch. Fan-Control Input. Drive FORCEON high for normal operation. Drive FORCEON low to force fan on. Current Source Positive Input. Connect to the anode of the external diodeconnected transistor. Do not leave DXP floating. Connect a 2200pF capacitor between DXP and DXN for noise filtering. Current Sink Negative Input. Connect to the cathode of the external diodeconnected transistor. DXN is internally biased to a diode voltage drop. Ground Positive Power Supply 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. Temperature Warning Output. WARN is an open-drain output that goes low when the sensed junction temperature is 15C higher than the fan trip threshold. Overtemperature Output. OT is an open-drain output that goes low when the sensed junction temperature is 30C higher than the fan trip threshold. Hysteresis Control Input. HYST is a three-level logic input for controlling the fandrive comparator's hysteresis. Connect HYST to GND for 4C hysteresis, to VDD for 12C hysteresis, or leave floating for 8C hysteresis. NAME FUNCTION
3
3
DXP
4 5, 7 6 8
4 7 8 10
DXN GND VDD FANOUT
-- --
2 6
WARN OT
--
9
HYST
Detailed Description
The MAX6668/MAX6670 are simple fan controllers/drivers 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 connect the fan to a power supply of higher than 12V nominal, 15V maximum.
Overtemperature Alarm Outputs
WARN Output (MAX6670 Only) WARN is an active-low, open-drain digital output that indicates when the external P-N junction's temperature exceeds 15C 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 temperature. OT Output (MAX6670 Only) OT is an active-low, open-drain digital output that indicates when the external P-N junction's temperature exceeds 30C above the fan trip threshold. OT serves as a thermal shutdown output to the system in case of excessive temperature rise.
FANOUT Driver and FORCEON Controller
FANOUT Fan-Driver Output FANOUT is 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 driving FORCEON low. FORCEON Fan-Control Input Drive FORCEON low 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.
4
Hysteresis Input
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 external P-N junction's temperature exceeds the factory-programmed
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Remote Temperature Switches with Integrated Fan Controller/Driver
trip temperature. As the cooling fan operates, the circuit 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 FANOUT pin turns the fan off, removing power from the fan. For the MAX6670, HYST is a three-level logic input for controlling the fan-drive comparator's hysteresis. Connect HYST to GND to select 4C hysteresis, to VDD to select 12C hysteresis, or leave floating to select 8C hysteresis. The MAX6668 has a built-in hysteresis of 8C. 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.
MAX6668/MAX6670
Table 1. Remote-Sensor Transistor Manufacturers
MANUFACTURER Central Semiconductor (USA) ON Semiconductor (USA) Rohm Semiconductor (USA) Samsung (Korea) Siemens (Germany) Zetex (England) MODEL NO. CMPT3904 2N3904, 2N3906 SST3904 KST3904-TF SMBT3904 FMMT3904CT-ND
Applications Information
Remote-Diode Selection
The MAX6668/MAX6670 directly measure the die temperature of CPUs and other ICs that have on-board temperature-sensing diodes (see Typical Operating Circuit) or they can measure the temperature of a discrete diode-connected transistor. For best accuracy, the discrete transistor should be a small-signal device with its collector and base connected together. Several satisfactory 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 voltage at the highest expected temperature must be greater than 0.25V at 10A, and at the lowest expected temperature, forward voltage must be less than 0.95V at 100A. Do not use large power transistors. Also, ensure that the base resistance is less than 100. Tight specifications for forward current gain (50 < BF < 150, for example) indicate that the manufacturer has good process controls and that the transistors have consistent VBE characteristics.
To minimize noise and other errors, follow the guidelines 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 deflection coils of a CRT. Also, do not route the traces across a fast memory bus, which can introduce +30C 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 highvoltage traces, such as +12VDC. Avoid leakage currents from PC board contamination, since a 20M leakage path from DXP to GND causes about +1C 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 possible 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 V DD to GND with a 1F capacitor located as close to VDD as possible. Add additional bypass capacitors for long VDD and GND lines.
Noise-Filtering Capacitor
In 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 Layout
The location of the remote-sensing junction in the system 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.
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Remote Temperature Switches with Integrated Fan Controller/Driver MAX6668/MAX6670
Pin Configurations
TRIP TEMPERATURE
TOP VIEW
TRIP TEMPERATURE - HYSTERESIS FANOUT
PGND
1
8 7
FANOUT GND VDD GND
MAX6668 MAX6670
TIME
FORCEON 2
MAX6668
DXP 3 6 5 DXN 4
Figure 1. Temperature Trip Threshold Hysteresis MAX
GND 10MILS 10MILS DXP MINIMUM 10MILS DXN 10MILS GND
PGND 1 WARN DXP DXN FORCEON 2 3 4 5
10 FANOUT 9 HYST VDD GND OT
MAX6670
8 7 6
MAX
Figure 2. Recommended DXP/DXN PC Traces
Typical Operating Circuit
+4.5V TO +12V
Chip Information
TRANSISTOR COUNT: 8113 PROCESS: BiCMOS
+3V TO +3.6V VDD
Ordering Information
VDD
CPU
DXP
FANOUT
PART
MAX6670
DXN WARN VDD
TEMP RANGE
PI NPA CK AG E 10 MAX 10 MAX 10 MAX 10 MAX 10 MAX 10 MAX 10 MAX 10 MAX
THRESHOLD ( C) 40 45 50 55 60 65 70 75
MAX6670AUB40 -40C to +125C MAX6670AUB45 -40C to +125C MAX6670AUB50 -40C to +125C MAX6670AUB55 -40C to +125C
HYST GND
OT PGND FORCEON VDD
MAX6670AUB60 -40C to +125C MAX6670AUB65 -40C to +125C MAX6670AUB70 -40C to +125C MAX6670AUB75 -40C to +125C
6
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Remote Temperature Switches with Integrated Fan Controller/Driver
Functional Diagrams
VDD
MAX6668/MAX6670
DXP TEMP SENSOR
FANOUT
CS
TFAN
PGND
DXN HYST 4C, 8C, 12C HYSTERESIS WARN
FORCEON TFAN +15C OT
MAX6670
TFAN +30C
GND
VDD
DXP TEMP SENSOR
FANOUT
CS
TFAN
PGND
DXN 8C HYSTERESIS
MAX6668
FORCEON
GND
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Remote Temperature Switches with Integrated Fan Controller/Driver MAX6668/MAX6670
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
4X S
8LUMAXD.EPS
8
8
INCHES DIM A A1 A2 b c D e E H MIN 0.002 0.030 MAX 0.043 0.006 0.037
MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95
y 0.500.1 0.60.1
E
H
1
0.60.1
1
D
L
S
BOTTOM VIEW
0.010 0.014 0.005 0.007 0.116 0.120 0.0256 BSC 0.116 0.120 0.188 0.198 0.016 0.026 6 0 0.0207 BSC
0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC
TOP VIEW
A2
A1
A
e
c b L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0036
J
1 1
e
10
4X S
10
INCHES MAX DIM MIN 0.043 A 0.006 A1 0.002 A2 0.030 0.037 D1 0.116 0.120 0.114 0.118 D2 0.116 E1 0.120 0.118 E2 0.114 0.199 H 0.187 L 0.0157 0.0275 L1 0.037 REF b 0.007 0.0106 e 0.0197 BSC c 0.0035 0.0078 0.0196 REF S 0 6
MILLIMETERS MAX MIN 1.10 0.15 0.05 0.75 0.95 3.05 2.95 3.00 2.89 3.05 2.95 2.89 3.00 4.75 5.05 0.40 0.70 0.940 REF 0.177 0.270 0.500 BSC 0.090 0.200 0.498 REF 0 6
H y 0.500.1 0.60.1
1
1
0.60.1
TOP VIEW
BOTTOM VIEW
D2 GAGE PLANE A2 A b D1 A1
E2 c E1 L1
L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 10L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0061
I
1 1
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.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
10LUMAX.EPS

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