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TC620CCOA Fiches technique(PDF) 4 Page - TelCom Semiconductor, Inc |
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TC620CCOA Fiches technique(HTML) 4 Page - TelCom Semiconductor, Inc |
4 / 6 page 2-18 TELCOM SEMICONDUCTOR, INC. 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. TYPICAL NTC THERMISTOR 010 20 30 40 50 100 70 TEMPERATURE ( °C) 0 50 60 150 200 250 300 350 Figure 4. Typical Thermistor Resistance vs. Temperature TC621 Thermistor Selection The TC621 uses an external thermistor to monitor the controlling temperature. A thermistor with a resistance value of approximately 100k Ω at 25°C 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 Ω resistor between HIGH TEMP (pin 2) and VDD (pin 8) sets the high tempera- ture trip point at +51 °C and a 49kΩ resistor on LOW TEMP (pin 3) sets the low temperature trip point to +41 °C. 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 tempera- ture 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. 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 appli- cation, 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. |
Numéro de pièce similaire - TC620CCOA |
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Description similaire - TC620CCOA |
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