M TC670 Tiny Predictive Fan Failure Detector Features General Description • Fan Wear-Out Detection for 2-Wire Linear-Controlled Fans • Replacement System for 3-Wire Fans • Fan Alert Signal when Fan Speed is below Programmed Threshold • CLEAR Capability for Eliminating False Alarm • Low Operating Current, 90 µA (typ.) • VDD Range 3.0V to 5.5V • Available in a 6-Pin SOT-23 Package The TC670 is an integrated fan speed sensor that predicts and/or detects fan failure, preventing thermal damage to systems with cooling fans. When the fan speed falls below a user-specified level, the TC670 asserts an ALERT signal. With this design, a critical minimum fan speed is determined by the user. The fan alert level is then set with a resistor divider on the THRESHOLD pin (Pin 1) of the TC670. When the minimum fan speed is reached, the ALERT pin (Pin 5) changes from a digital high to low. This failure detection works with all linear-controlled 2-wire fans. The TC670 eliminates the need for 3-wire fan solutions. Applications • • • • • • • A CLEAR option can be used to reset the ALERT signal, allowing the flexibility of connecting the ALERT output of the TC670 with other ALERT/FAULT interrupts in the system. This feature can be implemented so that false fan fault conditions do not initiate system shutdown. Protection for Linear-Controlled Fans Power Supplies Industrial Equipment PCs and Notebooks Data Storage Data Communications Equipment Instrumentation The TC670 is specified to operate over the full industrial temperature range of -40°C to +85°C. The TC670 is offered in a 6-pin SOT-23 pin package and consumes 90 µA (typ.) during operation. The spacesaving package and low power consumption make this device an ideal choice for systems requiring fan speed monitoring. Package Type THRESHOLD 1 GND 2 CLEAR 3 TC670 SOT-23A-6 6 SENSE 5 ALERT 4 VDD Typical Application Circuit +5V ALERT LED 4 V DD R4 0.1 µF 3 CLEAR From R3 Microcontroller 1 R2 C THRESHOLD 6 SENSE SENSE GND 2 2003 Microchip Technology Inc. +12V ALERT 5 DC DC FAN FAN RSENSE DS21688C-page 1 TC670 1.0 ELECTRICAL CHARACTERISTICS TABLE 1-1: PIN FUNCTION TABLE Symbol THRESHOLD Absolute Maximum Ratings† GND VDD...................................................................................6.0V CLEAR All Inputs and Outputs. ............ (GND − 0.3V) to (VDD + 0.3V) VDD Output Short-Circuit Current .................................continuous Description Analog Input Ground Terminal Digital Input Bias Supply Input Current at Input Pin ................................................... +/-2 mA ALERT Digital (Open-Drain) Output Current at Output Pin .............................................. +/-25 mA SENSE Analog Input Junction Temperature, TJ ............................................. 150°C ESD protection on all pins ..................................................≥ 4 kV Operating Temperature Range........................-40°C to +85°C Storage Temperature Range.........................-55°C to +150°C † Notice: Stresses above those listed under "Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. DC CHARACTERISTICS Electrical Specifications: Unless otherwise specified, all limits are specified at +25°C, VDD = 3.0V to 5.5V, CLEAR = Low. Boldface type specifications apply for temperature range of -40°C to +85°C. Parameters Sym Min Typ Max Units Conditions Supply Voltage VDD 3.0 — 5.5 V Supply Current IDD — 90 150 µA Logic Input High Level VIH 0.8VDD — — V Logic Input Low Level VIL — — 0.2VDD V VTH(SENSE) — 124 — mV RSENSE — 50 — kΩ Input Voltage Minimum — 0.0 — V Input Voltage Maximum — 2.4 — V Input Resistance — 100 — MΩ ALERTACC -10 — +10 % VDD = 3.0V Output Low Voltage VLOW — — 0.3 V ISINK = 2.5 mA Output Delay Time tDELAY — 176 — ms Specified Temperature Range TA -40 — +85 °C Operating Temperature Range TA -40 — +125 °C θJA — 230 — °C/W Power Supply CLEAR Input SENSE Input Input Level Threshold Voltage Input Resistance THRESHOLD Input Programmed Fan Speed Alert Accuracy (Note 1) ALERT Output Temperature Ranges Thermal Package Resistances Thermal Resistance, 6L-SOT-23 Note 1: The TC670 will operate properly over the entire power supply range of 3.0V to 5.5V. As VDD varies from 3.0V, accuracy will degrade based on the percentage of VDD, as shown in Section 2.0, “Typical Performance Curves”. DS21688C-page 2 2003 Microchip Technology Inc. TC670 2.0 TYPICAL PERFORMANCE CURVES Note: The graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. The performance characteristics listed herein are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. Note: Unless otherwise indicated, all limits are specified at +25°C, VDD = 3.0V to 5.5V, CLEAR = Low. 115 110 160 +90°C 100 +25°C 95 90 -45°C 85 140 ALERT VOUT LOW (mV) Supply Current (µA) 105 80 75 100 80 60 40 3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4 5.7 VDD = 5.5V 20 0 0.5 70 2.7 VDD = 3.0V 120 1 1.5 Supply Current vs. Supply VDD = 3.0V VDD = 2.7V VDD = 3.3V 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 177 VDD = 5.5V VDD = 5.0V 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 THRESHOLD Voltage (V) FIGURE 2-3: Voltage. Fan Speed vs. Threshold 2003 Microchip Technology Inc. Fan Speed vs. ALERTACC. FIGURE 2-5: VDD = 3.6V 0.25 4.5 ALERTACC (%) ALERT Output Delay Time (ms) Fan Speed (RPM) 0.00 4 2.50 Fan Speed vs. Threshold 15000 14000 13000 12000 11000 10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0 3.5 13000 12000 TA = -40˚C 11000 TA = +25˚C 10000 9000 8000 TA = +90˚C 7000 6000 5000 VDD = 3.0V 4000 3000 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0 THRESHOLD Voltage (V) FIGURE 2-2: Voltage. 3 ALERT VLOW vs. ALERT FIGURE 2-4: ISINK. FAN SPEED (RPM) Fan Speed (RPM) 15000 14000 13000 12000 11000 10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0 2.5 ALERT ISINK (mA) Supply Voltage (V) FIGURE 2-1: Voltage. 2 6.0 176 175 174 173 172 171 170 169 168 2.5 3.0 3.5 4.0 4.5 5.0 Power Supply Voltage (VDD) FIGURE 2-6: ALERT Output Delay vs. Power Supply Voltage. DS21688C-page 3 TC670 Note: Unless otherwise indicated, all limits are specified at +25°C, VDD = 3.0V to 5.5V, CLEAR = Low. FIGURE 2-7: CLEAR pin high to ALERT pin high Timing Diagram. DS21688C-page 4 2003 Microchip Technology Inc. TC670 3.0 PIN DESCRIPTIONS The descriptions of the pins are listed in Table 3-1. TABLE 3-1: PIN FUNCTION TABLE Pin No. Symbol 1 THRESHOLD 2 GND 3 CLEAR 4 VDD 5 ALERT Digital (Open-Drain) Output 6 SENSE Analog Input Description Analog Input Ground Terminal Digital Input Bias Supply Input 3.3 Digital Input (CLEAR) The CLEAR input is used to reset or blank the ALERT output. When the CLEAR input is driven high, the ALERT output will be high-impedance (the ALERT output requires a pull-up resistor). 3.4 Bias Supply Input (VDD) Bias Supply Input, 3.0V to 5.5V. The bias supply input should be bypassed to ground with a 0.1 µF ceramic capacitor. 3.5 Digital (Open-Drain) Output (ALERT) The voltage set at the THRESHOLD input represents the fan speed at which the TC670 will signal a fan speed warning by pulling the ALERT output low. The threshold voltage to fan speed correlation can be seen in Figures 2-2 and 2-3. The ALERT output is an open-drain output that requires an external pull-up resistor. The ALERT output is pulled low when the sensed fan speed (detected by the pulses occurring at the SENSE input) falls below the speed that is represented by the voltage at the THRESHOLD pin. The ALERT output is latched in this state until power is cycled or the CLEAR input is toggled. 3.2 3.6 3.1 Analog Input (THRESHOLD) Ground (GND) The GND pin (Pin 2) of the TC670 should be connected directly to the analog ground plane of the circuit board. Care should be taken to keep this pin away from switching signals, such as the fan excitation signals in order to avoid false signals on the SENSE pin. 2003 Microchip Technology Inc. Analog Input (SENSE) Voltage pulses, which are generated by the fan current flowing through a sense resistor, are detected at the SENSE pin and used to calculate the fan speed. DS21688C-page 5 TC670 4.0 DETAILED DESCRIPTION +5V The TC670 is an integrated fan speed sensor that predicts/detects fan failure, consequently preventing thermal damage to systems with cooling fans. When the fan speed falls below a user-programmed threshold level, the TC670 asserts an ALERT signal. This threshold is set with an external resistor divider network. 1 ALERT Logic R2 Frequency-toVoltage GND Bandgap Oscillator 50 kΩ C THRESHOLD 6 SENSE SENSE DC FAN FAN RSENSE SENSE 124 mV TC670 Block Diagram. As shown in Figure 4-1, the TC670 senses the fan pulses and internally converts those pulses from a frequency into an analog voltage. This voltage is then compared with the DC voltage at the THRESHOLD pin. If the converted frequency-to-voltage value from the fan's pulses falls below the threshold voltage, the ALERT output is pulled low. In a 3.0V system, the external fan alert level on the THRESHOLD pin can be designed from 0.0V (stalled fan) to 2.4V (for 13,000 RPM) to cover most of the common fan speeds. This failure detection system works with linear-controlled 2-wire fans and eliminates the need for 3-wire fans. The TC670 can also work with 3-wire fans either by using the SENSE circuit or by directly sensing the RPM output from the 3rd wire. A CLEAR pin is provided to allow the user to reset the ALERT pin status back to a high state. This clear option also allows the flexibility of connecting the ALERT output of the TC670 with other alert/fault interrupts in the system without having a risk of a system shutdown due to false fan fault condition. DS21688C-page 6 +12V ALERT 5 GND 2 Note: This typical application circuit uses a LED to indicate that a fan failure has occurred. FIGURE 4-2: FIGURE 4-1: CLEAR R3 CLEAR THRESHOLD R4 0.1 µF 3 VDD ALERT LED 4 V DD 4.1 Typical Application Circuit. SENSE Input As shown in Figure 4-2, the SENSE input (Pin 6) is connected to the sense resistor (RSENSE) through a capacitor (CSENSE). The low value current sensing resistor (R SENSE) is connected between the ground return leg of the fan and the fan bias ground. During normal fan operation, commutation occurs as each pole of the fan is energized. This causes the fan current to be an AC waveform with fast falling edges. These short, rapid changes in fan current cause a corresponding dV/dt voltage across the sense resistor, as well as a corresponding dI/dt current through the sense capacitor. The current through CSENSE is terminated with the internal 50 kΩ input resistance at the SENSE pin of the TC670. When positive-going fan pulses at the SENSE input are greater than 124 mV (typ.), the TC670 latches-in those voltage spikes. This 124 mV (typ.) SENSE input built-in threshold reduces false triggering errors caused by extraneous noise pulses associated with a running fan. The presence and frequency of these pulses is a direct indication of fan operation and fan speed. 2003 Microchip Technology Inc. TC670 The design of the proper input SENSE circuitry is a matter of scaling RSENSE to provide the necessary amount of gain and proper selection of the sensing capacitor. The following table (Table 4-1) lists some recommended values for RSENSE according to the nominal operating current of the fan. Please note that the current draw specified by the fan manufacturer may be a worst-case rating and not the fan’s nominal operating current. If the fan current falls between two of the values listed, it is recommended that the higher value resistor is used. TABLE 4-1: RECOMMENDED VALUES FOR RSENSE PER FIGURE 4-2 Nominal Fan Current (mA) RSENSE (Ω) 100 4.7 200 2.4 300 1.8 400 1.3 500 1.0 600 0.8 4.2.1 THRESHOLD CALIBRATION USING FAN’S FULL SCALE SPEED The fan should first be run at full speed. At full speed, the threshold voltage level should be adjusted until the ALERT output is asserted. With this full-scale value of the threshold voltage, the value can be scaled down to the fan fault speed as a percentage of the full speed. For example, if the fan full speed threshold voltage is 1.5V, then the fan fault threshold voltage at 30% of full speed would be 30% x 1.5V = 0.45V. 4.2.2 THRESHOLD CALIBRATION USING FAN’S MINIMUM ALLOWABLE SPEED ESTIMATE For a more exact fan fault trip point, the user can run the fan at its minimum allowed speed. At this speed, the threshold voltage can be adjusted until the ALERT output is asserted. 4.3 CLEAR Input A 0.1 µF ceramic capacitor is recommended for CSENSE. Smaller capacitor values will require larger sense resistors, whereas larger capacitors are more expensive and occupy more board space. The CLEAR input allows the user to reset the ALERT pin to a high status. This is an active-high input. Consequently, as long as CLEAR is high, ALERT will always be high as well. To allow ALERT to operate correctly, CLEAR must be held low. This feature can be implemented so that false fan fault conditions do not initiate system shutdown. 4.2 4.4 THRESHOLD Input The voltage at the THRESHOLD input sets the equivalent minimum allowable fan speed for the application. As shown in Section 2.0, “Typical Performance Curves”, the relationship between the threshold voltage and minimum fan speed is also power supply and temperature dependant. All the values for the threshold voltage that are shown in these graphs represent typical numbers and might not be optimized for all fans in all applications. To ensure accurate fan speed monitoring of a specific fan in a specific application, the user must perform a onetime correlation check with the prototype. There are two techniques that can be used to calibrate the system. One approach is to find the fan’s full-scale capability and mathematically estimate the minimum acceptable speed of the fan. A second technique is to identify the fan’s minimum speed and calibrate the threshold voltage accordingly. ALERT Output The ALERT output is an open-drain output capable of sinking 2.5 mA (typ). The ALERT output is asserted whenever the detected fan speed equals or falls below the equivalent voltage set at the threshold pin. The ALERT output is only deactivated once the CLEAR pin is brought to a high state. Although the absolute maximum sink current of this pin is 25 mA, it is recommended that the current sinking into the ALERT output does not exceed 20 mA. 4.5 Power Supply Input (VDD) To assure proper operation of the TC670 in a noisy environment where the fans are running, the VDD pin (Pin 4) must be decoupled with a 0.1 µF capacitor, as shown in Figure 4-1. This capacitor should be located as close to the TC670 VDD pin as possible, as well as being promptly terminated to the ground plane. A ceramic capacitor is recommended. 4.6 Ground Terminal (GND) The GND pin (Pin 2) of the TC670 should be connected directly to the analog ground plane of the circuit board. Care should be taken to keep this pin away from switching signals, such as the fan excitation signals in order to avoid false signals on the SENSE pin. 2003 Microchip Technology Inc. DS21688C-page 7 TC670 5.0 PACKAGE INFORMATION 5.1 Package Marking Information 6-Pin SOT-23A (EIAJ SC-74) Device 6 5 4 cdef 1 2 3 1 & 2 = part number code Part Number Code TC670ECH DA 3 = year and quarter code 4 = lot ID number 5.2 Taping Form Component Taping Orientation for 6-Pin SOT-23A (EIAJ SC-74) Devices User Direction of Feed Device Marking W P PIN 1 Carrier Tape, Number of Components Per Reel and Reel Size: Package 6-Pin SOT-23A DS21688C-page 8 Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size 8 mm 4 mm 3000 7 in. 2003 Microchip Technology Inc. TC670 5.3 Package Dimensions (6-Pin SOT-23) E E1 B p1 n D 1 α c A φ L β Units Dimension Limits n p MIN A2 A1 INCHES* NOM MAX MILLIMETERS NOM 6 0.95 1.90 0.90 1.18 0.90 1.10 0.00 0.08 2.60 2.80 1.50 1.63 2.80 2.95 0.35 0.45 0 5 0.09 0.15 0.35 0.43 0 5 0 5 MIN Number of Pins 6 Pitch .038 p1 Outside lead pitch (basic) .075 Overall Height A .035 .046 .057 Molded Package Thickness .035 .043 .051 A2 Standoff .000 .003 .006 A1 Overall Width E .102 .110 .118 Molded Package Width .059 .064 .069 E1 Overall Length D .110 .116 .122 Foot Length L .014 .018 .022 φ Foot Angle 0 5 10 c Lead Thickness .004 .006 .008 Lead Width B .014 .017 .020 Mold Draft Angle Top 0 5 10 α Mold Draft Angle Bottom 0 5 10 β *Controlling Parameter Notes: Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed .005" (0.127mm) per side. MAX 1.45 1.30 0.15 3.00 1.75 3.10 0.55 10 0.20 0.50 10 10 JEITA (formerly EIAJ) equivalent: SC-74A Drawing No. C04-120 2003 Microchip Technology Inc. DS21688C-page 9 TC670 NOTES: DS21688C-page 10 2003 Microchip Technology Inc. TC670 PRODUCT IDENTIFICATION SYSTEM To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office. PART NO. X XXXX Device Temperature Range Package Device: TC670: Temperature Range: E Package: CHTR: = SOT-23, Small Outline Transistor, 6-lead (Tape and Reel only) = Examples: a) TC670ECHTR: Predictive Fan Failure Detector, SOT-23 package. Predictive Fan Failure Detector -40°C to +85°C Sales and Support Data Sheets Products supported by a preliminary Data Sheet may have an errata sheet describing minor operational differences and recommended workarounds. To determine if an errata sheet exists for a particular device, please contact one of the following: 1. 2. 3. Your local Microchip sales office The Microchip Corporate Literature Center U.S. FAX: (480) 792-7277 The Microchip Worldwide Site (www.microchip.com) Please specify which device, revision of silicon and Data Sheet (include Literature #) you are using. Customer Notification System Register on our web site (www.microchip.com/cn) to receive the most current information on our products. 2003 Microchip Technology Inc. DS21688C-page11 TC670 NOTES: DS21688C-page 12 2003 Microchip Technology Inc. Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip's Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property. • Microchip is willing to work with the customer who is concerned about the integrity of their code. • Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.” Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. 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Microchip received QS-9000 quality system certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona in July 1999 and Mountain View, California in March 2002. The Company’s quality system processes and procedures are QS-9000 compliant for its PICmicro® 8-bit MCUs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, non-volatile memory and analog products. In addition, Microchip’s quality system for the design and manufacture of development systems is ISO 9001 certified. 2003 Microchip Technology Inc. DS21688C - page 13 Kontaktinformationen