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TMP63 Scheda tecnica(PDF) 14 Page - Texas Instruments |
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TMP63 Scheda tecnica(HTML) 14 Page - Texas Instruments |
14 / 28 page RBias VBias RTMP63 R1 R2 VTrip 14 TMP63 SNIS211C – OCTOBER 2019 – REVISED JUNE 2020 www.ti.com Product Folder Links: TMP63 Submit Documentation Feedback Copyright © 2019–2020, Texas Instruments Incorporated Typical Application (continued) 9.2.1.2.1 Thermal Protection With Comparator Use the TMP63 device along with a voltage reference, and a comparator to program the thermal protection. As shown in Figure 18, the output of the comparator remains low until the voltage of the thermistor divider, with RBIAS and RTMP63, rises above the threshold voltage set by R1 and R2. When the output goes high, the comparator signals an overtemperature warning signal. The engineer can also program the hysteresis to prevent the output from continuously toggling around the temperature threshold when the output returns low. Either a comparator with built-in hysteresis or feedback resistors may be used. Figure 18. Temperature Switch Using Voltage Divider and a Comparator 9.2.1.2.2 Thermal Foldback One application that uses the output voltage of the TMP63 in an active control circuit is thermal foldback. This is performed to reduce, or fold back, the current driving a string of LEDs, for example. At high temperatures, the LEDs begin to heat up due to environmental conditions and self heating. Thus, at a certain temperature threshold based on the LED's safe operating area, the driving current must be reduced to cool down the LEDs and prevent thermal runaway. The device voltage output increases with temperature when the output is in the lower position of the voltage divider and can provide a response used to fold back the current. Typically, the device holds the current at a specified level until a high temperature is reached, known as the knee point, at which the current must be rapidly reduced in order to continue operation. To better control the temperature/voltage sensitivity, the device uses a rail-to-rail operational amplifier. Figure 19 shows the temperature knee point where the foldback begins. The set by the reference voltage (2.5 V) at the positive input, and the feedback resistors set the response of the foldback curve. The foldback knee point may be chosen based on the output of the voltage divider and the corresponding temperature from Equation 5 (110°C, for example). The device uses a buffer between the voltage divider with RTMP63 and the input to the op amp to prevent loading and variations in VTEMP. |
Codice articolo simile - TMP63_V03 |
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Descrizione simile - TMP63_V03 |
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