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TC620CVOA Scheda tecnica(PDF) 5 Page - Microchip Technology |
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TC620CVOA Scheda tecnica(HTML) 5 Page - Microchip Technology |
5 / 14 page © 2006 Microchip Technology Inc. DS21439C-page 5 TC620/TC621 3.0 DETAILED DESCRIPTION The TC620 has a positive temperature coefficient tem- perature sensor and a dual threshold detector. Temper- ature set point programming is accomplished with external 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 set point values. As measured temperature increases, the LOW LIMIT output is driven high when temperature equals the LOW SET set point (±3°C max). If tempera- ture continues to climb, the HIGH LIMIT output is driven high when temperature equals the HIGH SET set point (Figure 3-1). 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. FIGURE 3-1: TC620/TC621 Input vs. Output Logic 3.1 Programming the TC620 The resistor values to achieve the desired trip point temperatures on HIGH SET and LOW SET are calculated using Equation 3-1: EQUATION 3-1: For example, a 50°C setting on either the HIGH SET or LOW SET input is calculated using Equation 3-2 as follows: EQUATION 3-2: Care must be taken to ensure the LOW SET program- ming 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 5°C lower than the HIGH SET temperature setting. Figure 3-2 can help the user obtain an estimate of the external resistor values required for the desired LOW SET and HIGH SET trip points. FIGURE 3-2: TC620 Sense Resistors vs. Trip Temperature 3.2 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 -2°C below the programmed settings (Figure 3-3). FIGURE 3-3: 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 2°C below the user’s setting. Low Set Point High Set Point Low Limit Output High Limit Output Control Output (Cool Option Control Output (Heat Option) Temperature RTRIP = 0.5997 x T 2.1312 Where: RTRIP = Programming resistor in Ohms T = The desired trip point temperature in degrees Kelvin. RSET = 0.5997 x ((50 + 273.15) 2.1312) = 133.6 k Ω TEMPERATURE (°C) -55 -35 -15 5 25 45 65 85 105 125 50 100 150 200 250 Set Point (Set Point 2°C) High Limit or Low Limit Output |
Codice articolo simile - TC620CVOA |
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Descrizione simile - TC620CVOA |
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