Remote Temperature Switches with Integrated Fan Controller/Driver

Transcription

1 9-233; Rev 2; /2 Remote Temperature Switches with Integrated General Description The remote-junction thermal switches with an internal power transistor drive a cooling fan rated for supply voltages up to +2V and 25mA. 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 are simple drop-in fan-control solutions for a variety of systems. The features an open-drain WARN output that goes active when the remote temperature exceeds the factory-programmed fan activation threshold by +5 C. The features an open-drain OT output that goes active when the remote temperature exceeds the factory-programmed threshold by +3 C. The provide a fan-control input,, that allows the fan to be driven externally, regardless of temperature. Available temperature thresholds range from +4 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 2 C using a three-level logic input on the. Temperature threshold accuracy is ± C (typ) and ±2.2 C (max) for remote-junction temperatures from +4 C to +75 C. The operate from a +3V to +3.6V power supply, and are specified over the automotive temperature range (-4 C to +25 C). The MAX6668 is offered in an 8-pin µmax package and the is available in a space-saving -pin µmax package. Notebook and Desktop Computers Network Switches PC Power Supplies Laboratory Instruments Card Racks Temperature Alarms Fan Controls Applications Features +2V, 25mA Integrated Fan Driver No Calibration Required Pin-Selectable 4 C, 8 C, or 2 C Hysteresis () Factory-Programmed Temperature Thresholds from +4 C to +75 C Overtemperature Warning Signals µa (typ) Supply Current Space-Saving 8-Pin and -Pin µmax Packages 2N394 PART C S 22pF Ordering Information TEMP RANGE +3.3V WARN PI N - PA C K A G E Ordering Information continued at end of data sheet. 25mA FAN kω kω T H R ESH - O L D ( C ) MAX6668AUA4-4 C to +25 C 8 µmax 4 MAX6668AUA45-4 C to +25 C 8 µmax 45 MAX6668AUA5-4 C to +25 C 8 µmax 5 MAX6668AUA6-4 C to +25 C 8 µmax 6 MAX6668AUA7-4 C to +25 C 8 µmax 7 MAX6668AUA75-4 C to +25 C 8 µmax 75 Typical Application Circuit +2V HYST OT Pin Configuration appears at end of data sheet. Typical Operating Circuit appears at end of data sheet. P Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS to...-.3v to +6V P to...-.3v to +.3V to...-.3v to +5V to...-.3v to +.8V, WARN, HYST,, OT...-.3V to ( +.3V) Current into,,,, WARN, HYST,, OT...±2mA Current into, P... ±3mA 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 Continuous Power Dissipation (T A = +7 C) 8-Pin µmax (derate 4.mW/ C above +7 C)...333mW -Pin µmax (derate 5.6mW/ C above +7 C)...444mW Operating Temperature Range...-4 C to +25 C Storage Temperature Range...-6 C to +5 C Junction Temperature...+5 C Lead Temperature (soldering, s)...+3 C ( = +3V to +3.6V, T A = -4 C to +25 C, unless otherwise noted. Typical values are at = +3.3V and T A = +25 C.) POWER SUPPLY PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Power-Supply Range V Average Supply Current I DD 2 µa Operating Current During sampling 4 65 µa Power-On Reset (POR) Threshold POR falling edge.5 2. V POR Threshold Hysteresis 5 mv TEMPERATURE SENSOR Temperature Threshold Accuracy Temperature Threshold Hysteresis WARN Temperature Threshold ( Only) OT Temperature Threshold ( Only) Supply Sensitivity of Temperature Threshold T RJ = +4 C to +75 C (Note ), T A = C to +85 C, = +3.3V T TH T RJ = +4 C to +75 C (Note ), T A = -4 C to +25 C, = +3.3V T HYST HYST = 4 HYST = float 8 HYST = 2 MAX ± ±2.2 ± ±4 Relative to temperature threshold +5 C Relative to temperature threshold +3 C C C.6 C/V Temperature Sample Frequency Hz FAN DRIVE OUTPUT Output Voltage Low V OL I SINK = 25mA.5 V Thermal Shutdown 7 C Thermal Shutdown Hysteresis 2 C LOGIC INPUT/OUTPUT Input High Voltage V IH.8 x V 2

3 ELECTRICAL CHARACTERISTICS (continued) ( = +3V to +3.6V, T A = -4 C to +25 C, unless otherwise noted. Typical values are at = +3.3V and T A = +25 C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS.2 x Input Low Voltage V IL V Input Bias Current V = or µa WARN, OT Output Voltage Low V OL I SINK = 6mA.5 V WARN, OT Output High Leakage Current Note : T RJ is the temperature of the remote P-N junction. (T A = +25 C, unless otherwise noted.) V (V) T A = +25 C CURRENT vs. VOLTAGE = +3.3V I (ma) I OH V WARN or V OT = +5.5V µa MAX6668/7 toc V (V) I = 25mA VOLTAGE vs. SUPPLY VOLTAGE T A = +5 C T A = +25 C (V) Typical Operating Characteristics T A = +65 C MAX6668/7 toc2 IDD (µa) SUPPLY CURRENT vs. TEMPERATURE = +3.3V, I = 25mA TEMPERATURE ( C) MAX6668/7 toc3 IDD (µa) SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX6668/7 toc4 PERCENTAGE OF SAMPLES (%) TEMPERATURE THRESHOLD ERROR AUB4 9 SAMPLES MAX6668/7 toc5 = (V) THRESHOLD ERROR ( C) 3

4 MAX6668 PIN NAME FUNCTION Pin Description P Power Ground. P is the power ground for the power MOSFET switch Fan-Control Input. Drive high for normal operation. Drive low to force fan on. Current Source Positive Input. Connect to the anode of the external diodeconnected transistor. Do not leave floating. Connect a 22pF capacitor between and for noise filtering. 4 4 Current Sink Negative Input. Connect to the cathode of the external diodeconnected transistor. is internally biased to a diode voltage drop. 5, 7 7 Ground 6 8 Positive Power Supply 8 Fan-Drive Output. is an open-drain power MOSFET that sinks up to 25mA current to turn on the fan when the sensed temperature exceeds the fan trip threshold or the fan is forced on by driving low. 2 WARN 6 OT 9 HYST Temperature Warning Output. WARN is an open-drain output that goes low when the sensed junction temperature is 5 C higher than the fan trip threshold. Overtemperature Output. OT is an open-drain output that goes low when the sensed junction temperature is 3 C 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 for 4 C hysteresis, to for 2 C hysteresis, or leave floating for 8 C hysteresis. Detailed Description The 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 +2V/25mA nominal) cooling fan to, a simple on/off fan-control system is created. Do not connect the fan to a power supply of higher than 2V nominal, 5V maximum. Driver and Controller Fan-Driver Output is an open-drain output that sinks greater than 25mA of current to turn on the fan, either when the fan trip threshold is exceeded or the fan is forced on by driving low. Fan-Control Input Drive low to turn on the fan when the 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 WARN Output ( Only) WARN is an active-low, open-drain digital output that indicates when the external P-N junction s temperature exceeds 5 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 temperature. OT Output ( Only) OT is an active-low, open-drain digital output that indicates when the external P-N junction s temperature exceeds 3 C above the fan trip threshold. OT serves as a thermal shutdown output to the system in case of excessive temperature rise. 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 pin goes active and powers the fan when the external P-N junction s temperature exceeds the factory-programmed 4

5 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 pin turns the fan off, removing power from the fan. For the, HYST is a three-level logic input for controlling the fan-drive comparator s hysteresis. Connect HYST to to select 4 C hysteresis, to to select 2 C hysteresis, or leave floating to select 8 C hysteresis. 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 shows the temperature trip threshold hysteresis. Applications Information Remote-Diode Selection The 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. The sensing transistor must be a small-signal type with a relatively high forward voltage. Otherwise, the input voltage range may be violated. The forward voltage at the highest expected temperature must be greater than.25v at µa, and at the lowest expected temperature, forward voltage must be less than.95v at µa. Do not use large power transistors. Also, ensure that the base resistance is less than Ω. Tight specifications for forward current gain (5 < B F < 5, for example) indicate that the manufacturer has good process controls and that the transistors have consistent V BE characteristics. Noise-Filtering Capacitor In noisy environments, high-frequency noise can be attenuated using an external 22pF capacitor located at the and pins. Larger capacitor values may be used for additional filtering, but do not exceed 33pF; excessive capacitance increases error. Figure 2 shows the recommended / PC traces. Bypassing and Layout The location of the remote-sensing junction in the system affects the s 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. Table. Remote-Sensor Transistor Manufacturers MANUFACTURER Central Semiconductor (USA) ON Semiconductor (USA) Rohm Semiconductor (USA) Samsung (Korea) Siemens (Germany) Zetex (England) CMPT394 MODEL NO. 2N394, 2N396 SST394 KST394-TF SMBT394 FMMT394CT-ND To minimize noise and other errors, follow the guidelines below: ) Place the as close as possible to the remote diode. In a noisy environment, such as a computer motherboard, this distance can be cm to 2cm (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 / traces next to the deflection coils of a CRT. Also, do not route the traces across a fast memory bus, which can introduce +3 C error or more, even with good filtering. 3) Route the and traces in parallel and in close proximity to each other, away from any highvoltage traces, such as +2VDC. Avoid leakage currents from PC board contamination, since a 2MΩ leakage path from to causes about + C error. 4) Connect guard traces to on either side of the / 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 / traces and other traces carrying high-frequency noise signals does not help reduce EMI. The s P is the ground return for the fan driver. Bypass to with a µf capacitor located as close to as possible. Add additional bypass capacitors for long and lines. 5

6 MAX6668 MILS TRIP TEMPERATURE TRIP TEMPERATURE HYSTERESIS TIME Figure. Temperature Trip Threshold Hysteresis MILS TOP VIEW P P WARN Pin Configurations 8 7 MAX µmax 9 8 HYST MILS MINIMUM MILS OT µmax Figure 2. Recommended / PC Traces Typical Operating Circuit +4.5V TO +2V Chip Information TRANSISTOR COUNT: 83 PROCESS: BiCMOS +3V TO +3.6V Ordering Information CPU PART TEMP RANGE PI N - PA C K A G E T H R ESH - O L D ( C ) WARN AUB4-4 C to +25 C µmax 4 AUB45-4 C to +25 C µmax 45 AUB5-4 C to +25 C µmax 5 AUB55-4 C to +25 C µmax 55 HYST OT AUB6-4 C to +25 C µmax 6 P AUB65-4 C to +25 C µmax 65 AUB7-4 C to +25 C µmax 7 AUB75-4 C to +25 C µmax 75 6

7 C S HYST TEMP SENSOR 4 C, 8 C, 2 C HYSTERESIS T FAN T FAN +5 C Functional Diagrams P WARN OT T FAN +3 C C S TEMP SENSOR T FAN P 8 C HYSTERESIS MAX6668 7

8 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 A2 8 ÿ.5±. D TOP VIEW E A H A 4X S BOTTOM VIEW 8 DIM A A MIN MAX BSC A2.3 b c D e E H L α S INCHES BSC MILLIMETERS MIN MAX BSC BSC 8LUMAXD.EPS e b c L α FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 8L umax/usop APPROVAL DOCUMENT CONTROL NO. REV J.6±. e ÿ.5±..6±. TOP VIEW 4X S H BOTTOM VIEW INCHES MILLIMETERS DIM A A MIN -.2 MAX.43.6 MIN -.5 MAX..5 A D D2 E E2 H L L b e c S α REF.94 REF BSC.5 BSC REF.498 REF 6 6 LUMAX.EPS D2 E2 GAGE PLANE A2 A c D b A α E L L FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, L umax/usop DOCUMENT CONTROL NO. 2-6 REV. I 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, 2 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. APPROVAL

9 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Maxim Integrated: MAX6668AUA5+