AS273 Over-Temperature Detector SEMICONDUCTOR Features Description ¥ Programmable to three different over-temperature thresholds ¥ 2.5 V temperature compensated bandgap reference trimmed to 1% ¥ Open collector output goes low on over-temp condition ¥ ¥ ±3¡C temperature accuracy The AS273 is a series of programmable over-temperature detectors. Each is internally composed of a precision 2.5 V shunt reference, a proportional-to-absolute temperature thermal sensor, a comparator with controlled hysteresis, and an open collector output that indicates an over-temp condition. The threshold for the over-temp signal can be set to any of three values on a given part by controlling the magnitude of the reference shunt current. ¥ Available with 5¡C or 10¡C of temperature hysteresis ¥ Available in a wide range of overtemp thresholds to fit most temperature monitoring applications ¥ Reference shunt current serves to program over-temp threshold Now available in the SOT-223 for improved substrate temperature sensing Pin Configuration Ñ 1 The packaging options available with the AS273 make it appealing to a wide variety of temperature-sensing applications. The TO-92 package can be mechanically clamped to a heat sink to monitor the temperature of power devices. The 8L-SOIC and SOT-223 surface mount packages allow for temperature sensing in high component density applications. Top view SOIC (D) OUT The AS273 has an excellent absolute temperature accuracy of ±3¡C for each of the three over-temp thresholds. The low power dissipation minimizes any temperature sensing errors due to self-heating. There is either 5¡C or 10¡C of temperature hysteresis to prevent bouncing when an over-temp condition is removed. TO-92 (LP) 8 VREF SOT-223 (G) OUT OUT N/C 2 7 DO NOT USE N/C 3 6 DO NOT USE N/C 4 5 GROUND ASTEC Semiconductor GROUND VREF 1 GROUND VREF AS273 Over-Temperature Detector Ordering Information AS273 D 1 D A Circuit Type: Over-Temperature Detector Packaging Option: A = Ammo Pack B = Bulk T = Tube 13 = Tape and Reel (13" Reel Dia) Temperature Option: (Refer to Table A) Table A – Temperature Options Code TOT1 D 40 F 75 G 90 H 105 TOT2 45 80 95 110 Package Style: D = SOIC G = SOT-223 LP = TO-92 TOT3 50 85 100 115 Hysteresis Option: 1 = 10°C 5 = 5°C Functional Block Diagram VREF 1 CURRENT PROGRAMMING OUT 3 + 2.5 V Ð 4 mV/K + Ð 2 GND Pin Function Description Pin Number Function 1 VREF 2.5 V shunt reference; current into VREF pin also programs over-temperature trip point to one of three TOT values 2 GND Circuit ground and silicon substrate 3 OUT Open collector output. Output low when die temperature exceeds programmed trip point ASTEC Semiconductor Description 2 Over-Temperature Detector AS273 Absolute Maximum Ratings Parameter Symbol Rating Unit VREF ±10 mA Output Current IOUT ±10 mA Output Voltage VOUT 18 V TO-92 PD 775 mW 8-SOIC PD 750 mW SOT-223 Reference Current Continuous Power Dissipation at 25¡C PD 1000 mW Junction Temperature TJ 150 ¡C Storage Temperature TSTG Ð65 to 150 ¡C TL 300 ¡C Lead Temp, Soldering 10 Seconds Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. Typical Thermal Resistances Package θJA θJC Typical Derating SOT-223 115¡C/W 8¡C/W 8.7 mW/¡C TO-92 160¡C/W 80¡C/W 6.3 mW/¡C 8L SOIC 175¡C/W 45¡C/W 5.7 mW/¡C ASTEC Semiconductor 3 AS273 Over-Temperature Detector Electrical Characteristics Electrical Characteristics are guaranteed over the full junction temperature range (0 to 125¡C). Ambient temperature must be derated based upon power dissipation and package thermal characteristics. Parameter Symbol Test Condition Min. Typ. Max. Unit Reference Voltage VREF IREF = 2 mA, TJ = 25¡C 2.500 2.525 2.550 V Load Regulation VId 0.65 mA ≤ IREF ≤ 5.5 mA 5 10 mV Average Temperature Coefficient ∆VREG/∆T 0.65 mA ≤ IREF ≤ 5.5 mA 75 Reference ppm/¡C Output Saturation Voltage VOL IOUT = 4 mA; TJ > TOT Breakdown Voltage BV IOUT = 100 µA; TJ < TOT Leakage Current IOH VOUT = 18 V; TJ < TOT 200 18 400 30 1 mV V 1000 nA Over-Temp Sensing Temperature Accuracy Hysteresis TOT(1) 0.7 mA ≤ IREF ≤ 1.3 mA Ð3 +3 ¡C TOT(2) 1.55 mA ≤ IREF ≤ 2.6 mA Ð3 +3 ¡C TOT(3) 3.0 mA ≤ IREF ≤ 5.0 mA Ð3 +3 ¡C HOT Percentage Error in Nominal Hysteresis Ð30 +30 % Test Circuit +5V RLOAD 2 kΩ VREF OUT AS273 IREF GND Figure 1. Test Circuit for Output Hysteresis Curve ASTEC Semiconductor 4 Over-Temperature Detector AS273 Typical Performance Curves Minimum Reference Current for Regulation Turn-on Characteristic of Reference 3 300 275 Reference Voltage, VREF (V) Turn-on Current, IREF (µA) 250 225 200 175 150 2 1 125 0 100 0 25 50 75 100 125 0 150 200 400 600 800 1000 Reference Current, IREF (µA) Junction Temperature, TJ (°C) Figure 2 Figure 3 Load Regulation of Reference Over-temperature Temperature Regulation of Reference 2.55 10 9 8 Load Regulation (mV) Reference Voltage, VREF (V) 2.54 2.53 2.52 7 6 5 4 3 2 2.51 1 2.50 0 0 25 50 75 100 125 150 0 Junction Temperature, TJ (°C) 50 75 100 Junction Temperature, TJ (°C) Figure 4 ASTEC Semiconductor 25 Figure 5 5 125 150 AS273 Over-Temperature Detector Typical Performance Curves Output Saturation Characteristic Typical Over-temperature Threshold Distribution – Option G 900 50 IREF = 1 mA IREF = 2 mA IREF = 4 mA 40 700 Distribution of Population (%) Output Voltage, VOUT (mV) 800 0°C 600 25°C 50°C 500 75°C 400 100°C 125°C 300 30 20 10 200 100 0.001 0 0.01 0.1 1 88 10 90 Saturation Current, IOUT (mA) 92 94 96 98 Over-temperature Threshold (°C) Figure 6 Figure 7 Thermal Response by Package in a Stirred Oil Bath 120 Percent of Thermal Equilibrium (%) 100 SOT-223 80 TO-92 8L SOIC 60 40 20 0 0 2 4 6 Time (s) Figure 8 ASTEC Semiconductor 6 8 10 12 100 102 Over-Temperature Detector AS273 reference voltage corresponding to the overtemperature threshold. When the PTAT voltage exceeds the reference voltage, the comparator is tripped and an over-temp signal is given to the output. The output consists of an open collector transistor that pulls low on an over-temp condition. Built into the comparator is temperature hysteresis, which keeps the over-temp signal until the junction temperature has fallen 5¡C (or 10¡C) below the over-temp threshold. Figure 9 shows the output of the AS273 (with 10¡C of hysteresis) over a range of junction temperature. Theory of Operation The AS273 is an over-temperature detector that gives an over-temp signal when the device junction temperature exceeds a programmed over-temp threshold. Over-temp threshold programming is accomplished by controlling the magnitude of the reference shunt current. Over-temperature Condition Internal to the AS273 is a temperature sensor which creates a voltage proportional to the absolute temperature (PTAT) of the die. This PTAT voltage is compared with a fraction of the IREF = 4 mA 5 0 IREF = 2 mA Output Voltage, V 5 0 IREF = 1 mA 5 0 OT1-10 OT1-5 OT1 OT2 Junction Temperature, TJ (°C) Figure 9. Temperature Characteristic of Output with 10¡C of Hysteresis ASTEC Semiconductor 7 OT3 AS273 Over-Temperature Detector old based on the magnitude of that current. Figure 10 illustrates the ranges of reference shunt current, IREF, associated with each of the three over-temp thresholds, OT1, OT2 and OT3. Current Programming There are three different over-temp thresholds for each AS273. The detector senses the amount of current being shunted through the 2.5 V reference of pin 1 and programs an over-temp thresh- Over-temperature Thresholds (°C) OT3 OT2 Transition Regions OT1 Output Disabled 0 1 2 3 4 Reference Shunt Current, IREF (mA) Figure 10. Reference Shunt Current Programming Ranges of Over-temperature Thresholds ASTEC Semiconductor 8 5 Over-Temperature Detector AS273 Typical Detector Applications VCC Over-Temperature Detector The AS273 senses the ambient temperature and turns on its open collector output to indicate an over-temp condition. Each AS273 can be programmed to any one of its three over-temp thresholds by forcing a different range of current into the reference pin. R1 R2 VOUT REF OUT AS273 GND Figure 11. Dual Speed Fan Control +12 V The diagram of Figure 12 shows an easy way to implement smart fan control. When the temperature is below the over-temp trip point set by R1, the detectorÕs open collector output is off. Therefore, the fan speed is controlled by the ratio between R2 and R3. When the temperature exceeds the over-temp set point, the open collector is turned on, and fan motor runs at its full speed. R2 10 kΩ R1 9.1 kΩ Q1 REF OUT R3 10 kΩ AS273 GND Figure 12. ASTEC Semiconductor M 9 AS273 Over-Temperature Detector Over-Temperature Protection with Latch (Low Current) VCC The diagram of Figure 13 illustrates how a power supply can be shut down with a simple twotransistor latch. When the programmed overtemp is reached, the open collector output of the AS273 enables the latch and pulls VCC below the under-voltage threshold of the AS3842, shutting off the AS3842. The latch can be disabled only with a power reset. COMP VREG VFB ICC = 400 mA MAX. VCC SENSE OUT RT/CT GND + R2 350 Ω AS3842 R1 1k REF OUT AS273 R3 350 Ω GND Figure 13. Over-Temperature Protection with Hysteresis V BULK In this over-temperature circuit, the hysteresis of the AS273 is used to automatically restart the power supply after the temperature drops below the hysteresis temperature window. R1 supplies the current to power the AS273 after the AS3842 and the power supply are shut down. R2 and the external zener set the over-temperature trip point. R1 R2 COMP REF VREG OUT VFB AS273 VCC SENSE OUT GND RT/CT GND AS3842 Figure 14. ASTEC Semiconductor 10 Over-Temperature Detector AS273 Adjustable Hysteresis Temperature Detector VCC The hysteresis of the AS273 can be increased by reprogramming the device to a lower temperature set point upon over-temp. A higher temperature is set by R1. When the temperature exceeds the high-temp set point, the open collector output is turned on and allows R2 to rob current from the reference pin and resets the AS273 to the lowtemp set point. As a result, the hysteresis escalates by the difference between the high-temp and the low-temp set points. R1 R2 VOUT REF OUT AS273 GND Figure 15. Three-State Temperature Sensor VCC In the Three-State Temperature Sensor shown in Figure 16, a low-temp trip point is selected by R1 and a high-temp trip point is selected by the twotransistor latch. When the temperature is below the low-temp set point, VOUT is in the high state (VOUT = 5.0 V). When the temperature exceeds the low-temp set point, the two-transistor latch is set and VOUT is pulled low (VOUT = 2.5 V). The latch also supplies extra current to the reference pin to reset the IC to sense a higher temperature. Once the high-temp is reached, the output will turn ÒonÓ (VOUT = 0.2 V). This circuit is highly useful in applications where a stand-by, a warning and a shut-down state are required. +5 V R1 2.4 kΩ R2 1 kΩ R3 1.5 kΩ R5 2 kΩ R4 470 Ω R6 500 Ω VO REF OUT + C1 1 µF AS273 GND Stand-by State: Warning State: Shut-down State: T < T1, T2 T1 < T < T2 T1, T2 < T Figure 16. ASTEC Semiconductor 11 VO = 5.0 V VO = 2.5 V VO = 0.2 V AS273 Over-Temperature Detector Notes ASTEC Semiconductor 12