ZHCSKB0 October   2019 TMP63

ADVANCE INFORMATION for pre-production products; subject to change without notice.  

  1. 特性
  2. 应用
  3. 说明
    1.     Device Images
      1.      典型实施电路
      2.      典型电阻与环境温度间的关系
  4. 修订历史记录
  5. Pin Configuration and Functions
    1.     Pin Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
    4. 7.4 Device Functional Modes
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Thermistor Biasing Circuits
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Thermal Protection With Comparator
          2. 8.2.1.2.2 Thermal Foldback
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 接收文档更新通知
    2. 11.2 支持资源
    3. 11.3 商标
    4. 11.4 静电放电警告
    5. 11.5 Glossary
  12. 12机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

Detailed Design Procedure

The resistive circuit divider method produces an output voltage (VTEMP) scaled according to the bias voltage (VBIAS). When VBIAS is also used as the reference voltage of the ADC, any fluctuations or tolerance error due to the voltage supply will be canceled and will not affect the temperature accuracy. This type of configuration is shown in Figure 3. Equation 2 describes the output voltage (VTEMP) based on the variable resistance of the TMP63 (RTMP63) and bias resistor (RBIAS). The ADC code that corresponds to that output voltage, ADC full-scale range, and ADC resolution is given in Equation 3.

TMP63 App_VDiv_ADC.gifFigure 3. TMP63 Voltage Divider With an ADC
Equation 2. TMP63 VDiv_ADC_EQ1.gif
Equation 3. TMP63 VDiv_ADC_EQ2.gif

where

  • FSR is the full-scale range of the ADC, which is the voltage at REF to GND (VREF)
  • n is the resolution of the ADC

Equation 4 shows whenever VREF = VBIAS, VBIAS cancels out.

Equation 4. TMP63 VDiv_ADC_EQ3.gif

The engineer can use a polynomial equation or a LUT to extract the temperature reading based on the ADC code read in the microcontroller.

The cancellation of VBIAS is one benefit to using a voltage-divider (ratiometric approach), but the sensitivity of the output voltage of the divider circuit cannot increase much. Therefore, not all of the ADC codes will be used due to the small voltage output range compared to the FSR. This application is very common, however, and is simple to implement.

The engineer can use a current source-based circuit, like the one shown in Figure 4, to have better control over the sensitivity of the output voltage and achieve higher accuracy. In this case, the output voltage is simply V = I × R. For example, if a current source of 40 µA is used with the TMP63, the output voltage will span approximately 5.5 V and will have a gain up to 40 mV/°C. Having control over the voltage range and sensitivity allows for full utilization of the ADC codes and full-scale range. Based on the bias current, the temperature voltage is shown in Figure 5. Similar to the ratiometric approach above, if the ADC has a built-in current source that shares the same bias as the reference voltage of the ADC, the tolerance of the supply current cancels out. In this case, a precision ADC is not required. This method yields the best accuracy, but can increase the system implementation cost.

TMP63 TMP63_Current_Source.gifFigure 4. TMP63 Biasing Circuit With Current Source
TMP63 TMP63_IBias_Curves.gifFigure 5. TMP63 Temperature Voltage With Varying Current Sources

In comparison to the non-linear NTC thermistor in a voltage divider, the TMP63 has an enhanced linear output characteristic. The two voltage divider circuits with and without a linearization parallel resistor, RP, are shown in Figure 6. Consider an example where VBIAS = 5 V, RBIAS = 10 kΩ, and a parallel resistor (RP) is used with the NTC thermistor (RNTC) to linearize the output voltage with an additional 10-kΩ resistor. The TMP63 produces a linear curve across the entire temperature range while the NTC curve is only linear across a small temperature region. When the parallel resistor (RP) is added to the NTC circuit, the added resistor makes the curve much more linear but greatly affects the output voltage range.

TMP63 TMP63_vs_NTC.gifFigure 6. TMP63 vs. NTC With Linearization Resistor (RP) Voltage Divider Circuits