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| 1 TC620 TC621 5V, DUAL TRIP POINT TEMPERATURE SENSORS FEATURES s s s s User-Programmable Hysteresis and Temperature Set Point Easily Programs with 2 External Resistors Wide Temperature Detection Range ................ - 40C to +125C (TC620/621CVx) External Thermistor for Remote Sensing Applications (TC621x) GENERAL DESCRIPTION The TC620 and TC621 are programmable logic output temperature detectors designed for use in thermal management applications. The TC620 features an on-board temperature sensor, while the TC621 connects to an external NTC thermistor for remote sensing applications. Both devices feature dual thermal interrupt outputs (HIGH LIMIT and LOW LIMIT), each of which program with a single external resistor. On the TC620, these outputs are driven active (high) when measured temperature equals the user-programmed limits. The CONTROL (hysteresis) output is driven high when temperature equals the high limit setting, and returns low when temperature falls below the low limit setting. This output can be used to provide simple ON/OFF control to a cooling fan or heater. The TC621 provides the same output functions except that the logical states are inverted. The TC620/621 are usable over a maximum temperature range of - 40C to +125C. Ambient Temperature - 40C to +85C - 40C to +85C 2 3 4 5 6 7 APPLICATIONS s s s s Power Supply Overtemperature Detection Consumer Equipment Temperature Regulators CPU Thermal Protection ORDERING INFORMATION Part No. TC620x*COA TC620x*CPA TC620x*EOA TC620x*EPA TC620CVOA TC621x*COA TC621x*CPA Package Ambient Temperature 8-Pin SOIC 0C to +70C 8-Pin Plastic DIP 0C to +70C 8-Pin SOIC - 40C to +85C 8-Pin Plastic DIP - 40C to +85C 8-Pin SOIC - 40C to +125C 8-Pin SOIC 0C to +70C 8-Pin Plastic DIP 0C to +70C Part No. TC621x*EOA TC621x*EPA Package 8-Pin SOIC 8-Pin Plastic DIP *The part code will be C or H (see Functional Block Diagram, below, and page 2). FUNCTIONAL BLOCK DIAGRAM VDD 8 Temp to Voltage Converter 1 Thermistor Interface Circuit 8 VDD TC620 4 THERMISTOR TC621 4 + 2 LOW SET VREF GEN 7 LOW LIMIT HIGH SET 2 VREF GEN + - 7 HIGH LIMIT - VREF VREF + HIGH SET 3 VREF GEN 6 HIGH LIMIT LOW SET R Q S Q 5 CONTROL* 3 VREF GEN + - R Q S Q 6 LOW LIMIT - 5 CONTROL* *Suffix code "C" denotes cooling option (high true CONTROL output); suffix code "H" denotes heating option (low true CONTROL output). 8 TC620/1-9 11/4/96 TELCOM SEMICONDUCTOR, INC. 2-15 5V, DUAL TRIP POINT TEMPERATURE SENSORS TC620 TC621 ABSOLUTE MAXIMUM RATINGS* Package Power Dissipation (TA 70C) PDIP ............................................................... 730mW SOIC ............................................................... 470mW Derating Factors Plastic ............................................................8mW/C Supply Voltage ............................................................20V Input Voltage Any Input ....... (GND - 0.3V) to (VDD +0.3V) Operating Temperature M Version ....................................... - 55C to +125C V Version ........................................ - 40C to +125C E Version .......................................... - 40C to +85C C Version ............................................... 0C to +70C Maximum Chip Temperature ................................. +150C Storage Temperature ............................ - 65C to +150C Lead Temperature (Soldering, 10 sec) ................. +300C *Static-sensitive device. Unused devices must be stored in conductive material. Protect devices from static discharge and static fields. Stresses above 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 above those indicated in the operation sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS: TA = 25C, unless otherwise specified. Parameter Supply Voltage Range Supply Current Output Resistance Output Current Output Current Absolute Accuracy Conditions 5V VDD 18V Output High or Low, 5V VDD 18V Temp Sensed Source/Sink Cool/Heat Source/Sink T = Programmed Temperature Min 4.5 -- -- -- -- T-3 Typ -- 270 400 -- -- T Max 18 400 1000 1 1 T+3 Unit V A mA mA C PIN CONFIGURATIONS (DIP and SOIC) NC 1 LOW SET 2 HIGH SET 3 GND 4 8 VDD 7 LOW LIMIT NC LOW SET HIGH SET 1 2 3 4 8 7 VDD LOW LIMIT HIGH LIMIT CONTROL TC620xCPA TC620xEPA 6 HIGH LIMIT 5 CONTROL GND TC620xCOA TC620xEOA TC620CVOA 6 5 NC 1 HIGH SET 2 LOW SET 3 GND 4 8 7 VDD HIGH LIMIT LOW LIMIT CONTROL NC HIGH SET LOW SET 1 2 3 4 8 7 VDD HIGH LIMIT LOW LIMIT CONTROL TC621xCPA TC621xEPA 6 5 GND TC621xCOA TC621xEOA 6 5 2-16 TELCOM SEMICONDUCTOR, INC. 5V, DUAL TRIP POINT TEMPERATURE SENSORS TC620 TC621 DETAILED DESCRIPTION The TC620/621 consists of a positive temperature coefficient (PTC) temperature sensor, and a dual threshold detector. Temperature setpoint programming is easily accomplished with external programming resistors from the HIGH SET and LOW SET inputs to VDD. The HIGH LIMIT and LOW LIMIT outputs remain low as long as measured temperature is below setpoint values. As measured temperature increases, the LOW LIMIT output is driven high when temperature equals the LOW SET setpoint (3C max). If temperature continues to climb, the HIGH LIMIT output is driven high when temperature equals the HIGH SET setpoint (Figure 1). The CONTROL (hysteresis) output is latched in its active state at the temperature specified by the HIGH SET resistor. CONTROL is maintained active until temperature falls to the value specified by the LOW SET resistor. Care must be taken to ensure the LOW SET programming resistor is a smaller value than the HIGH SET programming resistor. Failure to do this will result in erroneous operation of the CONTROL output. Care must also be taken to ensure the LOW SET temperature setting is at least 5C lower than the HIGH SET temperature setting. That is: LOW SET HIGH SET - 5C The nomograph of Figure 2 can help the user obtain an estimate of the external resistor values required for the desired LOW SET and HIGH SET trip points. 250 1 2 3 4 RESISTANCE (k) 200 150 HIGH SET POINT TEMPERATURE LOW SET POINT LOW LIMIT OUTPUT HIGH LIMIT OUTPUT CONTROL OUTPUT (COOL OPTION) CONTROL OUTPUT (HEAT OPTION) 100 50 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C) Figure 2. TC620 Sense Resistors vs. Trip Temperature 5 6 Built-in Hysteresis To prevent output "chattering" when measured temperature is at (or near) the programmed trip point values, the LOW SET and HIGH SET inputs each have built-in hysteresis of - 2C below the programmed settings (Figure 3). Figure 1: TC620/621 Input vs. Output Logic Programming The TC620 The resistor values to achieve the desired trip-point temperatures on HIGH SET and LOW SET are calculated using EQUATION 1 below: RTRIP = 0.5997 x T 2.1312 Where: Rtrip = Programming resistor in Ohms T = The desired trip point temperature in degrees Kelvin Equation 1. SET POINT (SET POINT - 2C) HIGH LIMIT or LOW LIMIT Output 7 For example, a 50C setting on either the HIGH SET or LOW SET input is calculated using Equation 1 as follows: Rset = 0.5997 x ((50 + 273.15)2.1312) = 133.6k Figure 3: Built-in Hysteresis on Low Limit and High Limit Outputs As shown, the outputs remain in their active state (hysteresis) until temperature falls an additional 2C below the user's setting. 8 TELCOM SEMICONDUCTOR, INC. 2-17 5V, DUAL TRIP POINT TEMPERATURE SENSORS TC620 TC621 Using The TC621 The TC621 operation is identical to that of the TC620, but requires an external NTC thermistor. Use the resistance versus temperature curve of the thermistor to determine the values of the programming resistors. Note that the pin numbers for the HIGH SET and LOW SET programming resistors for the TC621 are reversed versus that of the TC620 (i.e. the resistor value on HIGH SET [pin 2] should always be lower than the one connected to LOW SET [pin 3]). Also note that the outputs of the TC621 are LOW TRUE when used with an NTC thermistor. APPLICATIONS Dual Speed Temperature Control The Dual Speed Temperature Control uses a TC620 and a TC4469 quad driver. Two of the drivers are configured in a simple oscillator. When the temperature is below the LOW TEMP set point, the output of the driver is OFF. When the temperature exceeds the LOW TEMP set point, the TC4469 gates the oscillator signal to the outputs of the driver. This square wave signal modulates the remaining outputs and drives the motor at a low speed. If this speed cannot keep the temperature below the HIGH TEMP set point, then the driver turns on continuously which increases the fan speed to high. The TC620 will monitor the temperature and only allow the fan to operate when needed, and at the required speed to maintain the desired temperature. A higher power option can be designed by adding a resistor and a power MOSFET. TC621 Thermistor Selection The TC621 uses an external thermistor to monitor the controlling temperature. A thermistor with a resistance value of approximately 100k at 25C is recommended. A temperature setpoint is selected by picking a resistor whose value is equal to the resistance of the thermistor at the desired temperature. For example, a 30k resistor between HIGH TEMP (pin 2) and VDD (pin 8) sets the high temperature trip point at +51C and a 49k resistor on LOW TEMP (pin 3) sets the low temperature trip point to +41C. Temperature Controlled Fan In this application, a high and a low temperature is selected by two `set' resistors. The TC620 monitors the ambient temperature and turns the FET switch on when the temperature exceeds the HIGH TEMP set point. The fan remains on until the temperature decreases to the LOW TEMP set point. This provides the hysteresis. In this application, the fan turns on only when required. The TC621 uses an external thermistor to monitor the ambient temperature. This adds one part, but allows more flexibility in location of the sensor. TC620/621 Outputs Both devices have complimentary output stages. They are rated at a source or sink current of 1mA maximum. TYPICAL NTC THERMISTOR 350 300 THERMISTOR RESISTANCE (k) 250 200 150 100 50 0 0 10 20 30 40 50 60 70 TEMPERATURE (C) Figure 4. Typical Thermistor Resistance vs. Temperature 2-18 TELCOM SEMICONDUCTOR, INC. 5V, DUAL TRIP POINT TEMPERATURE SENSORS TC620 TC621 +12V VMOTOR 1 0.1 F LOW TEMP 30C 2 3 1 5 8 6 TC620 7 4 TEMPERATURE SCALE 0C - 30C (FAN OFF) 30C - 50C (FAN LOW) 50C - UP (FAN HIGH) 1 F 1N4148 10 F 14 2 1 3 5 8 TC4469 13 4 6 9 10 11 12 1M 100k 50 50 pF 2 3 4 FAN MOTOR MOSFET HIGH TEMP 50C 1N4148 HIGHER POWER OPTION 10k 7 FAN MOTOR Figure 5. +12V +12V THERMISTOR (NTC) 1 LOW TEMP 2 3 HIGH TEMP 4 TC620 8 7 6 5 FAN MOTOR HIGH TEMP 1 2 3 TC621 8 7 6 5 FAN MOTOR MTP3055E LOW TEMP 4 MTP3055E 5 6 Figure 6. 4.5V TO 18V HIGH TEMP LOW TEMP 1 2 3 4 8 7 6 5 1 2 3 4 5 6 7 14 13 12 11 10 9 8 1k TC620 TC4469 HIGH TEMP WARNING 1k LOW TEMP WARNING 7 HEATING/COOLING EQUIPMENT Figure 7. TC620 Heating/Cooling Application 8 2-19 TELCOM SEMICONDUCTOR, INC. 5V, DUAL TRIP POINT TEMPERATURE SENSORS TC620 TC621 4.5V TO 18V HIGH TEMP LOW TEMP 1 2 3 4 TC620 8 7 6 5 1 2 3 4 5 6 7 TC4469 14 13 12 11 10 9 8 1k HIGH TEMP WARNING 1k LOW TEMP WARNING HEATING/COOLING EQUIPMENT Figure 8. TC620 Heating/Cooling Application 2-20 TELCOM SEMICONDUCTOR, INC. |
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