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LM19CIZ датащи(PDF) 5 Page - National Semiconductor (TI) |
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LM19CIZ датащи(HTML) 5 Page - National Semiconductor (TI) |
5 / 8 page 1.0 LM19 Transfer Function (Continued) 2.0 Mounting The LM19 can be applied easily in the same way as other integrated-circuit temperature sensors. It can be glued or cemented to a surface. The temperature that the LM19 is sensing will be within about +0.02˚C of the surface tempera- ture to which the LM19’s leads are attached. This presumes that the ambient air temperature is almost the same as the surface temperature; if the air temperature were much higher or lower than the surface temperature, the actual temperature measured would be at an intermediate temperature between the surface temperature and the air temperature. To ensure good thermal conductivity the backside of the LM19 die is directly attached to the GND pin. The temper- tures of the lands and traces to the other leads of the LM19 will also affect the temperature that is being sensed. Alternatively, the LM19 can be mounted inside a sealed-end metal tube, and can then be dipped into a bath or screwed into a threaded hole in a tank. As with any IC, the LM19 and accompanying wiring and circuits must be kept insulated and dry, to avoid leakage and corrosion. This is especially true if the circuit may operate at cold temperatures where conden- sation can occur. Printed-circuit coatings and varnishes such as Humiseal and epoxy paints or dips are often used to ensure that moisture cannot corrode the LM19 or its connec- tions. The thermal resistance junction to ambient ( θ JA) is the pa- rameter used to calculate the rise of a device junction tem- perature due to its power dissipation. For the LM19 the equation used to calculate the rise in the die temperature is as follows: T J =TA + θ JA [(V + I Q)+(V + −V O)IL] where I Q is the quiescent current and ILis the load current on the output. Since the LM19’s junction temperature is the actual temperature being measured care should be taken to minimize the load current that the LM19 is required to drive. The tables shown in Figure 3 summarize the rise in die temperature of the LM19 without any loading, and the ther- mal resistance for different conditions. 3.0 Capacitive Loads The LM19 handles capacitive loading well. Without any pre- cautions, the LM19 can drive any capacitive load less than 300 pF as shown in Figure 4. Over the specified temperature range the LM19 has a maximum output impedance of 160 Ω. In an extremely noisy environment it may be necessary to add some filtering to minimize noise pickup. It is recom- mended that 0.1 µF be added from V + to GND to bypass the power supply voltage, as shown in Figure 5. In a noisy environment it may even be necessary to add a capacitor from the output to ground with a series resistor as shown in Figure 5. A 1 µF output capacitor with the 160 Ω maximum output impedance and a 200 Ω series resistor will form a 442 Hz lowpass filter. Since the thermal time constant of the LM19 is much slower, the overall response time of the LM19 will not be significantly affected. Temperature Range Linear Equation V O= Maximum Deviation of Linear Equation from Parabolic Equation (˚C) T min (˚C) T max (˚C) −55 +130 −11.79 mV/˚C x T + 1.8528 V ±1.41 −40 +110 −11.77 mV/˚C x T + 1.8577 V ±0.93 −30 +100 −11.77 mV/˚C x T + 1.8605 V ±0.70 -40 +85 −11.67 mV/˚C x T + 1.8583 V ±0.65 −10 +65 −11.71 mV/˚C x T + 1.8641 V ±0.23 +35 +45 −11.81 mV/˚C x T + 1.8701 V ±0.004 +20 +30 −11.69 mV/˚C x T + 1.8663 V ±0.004 FIGURE 2. First Order Equations Optimized For Different Temperature Ranges. TO-92 TO-92 no heat sink small heat fin θ JA T J −TA θ JA T J −TA (˚C/W) (˚C) (˚C/W) (˚C) Still air 150 TBD TBD TBD Moving air TBD TBD TBD TBD FIGURE 3. Temperature Rise of LM19 Due to Self-Heating and Thermal Resistance ( θ JA) 20004015 FIGURE 4. LM19 No Decoupling Required for Capacitive Loads Less than 300 pF. www.national.com 5 |
Аналогичный номер детали - LM19CIZ |
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Аналогичное описание - LM19CIZ |
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