SNAS758A February   2025  – June 2025 HDC3120

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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
    6. 6.6 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Device Power-Up
      2. 7.3.2 Device Disable and Enable
      3. 7.3.3 Conversion of the Signal Output
        1. 7.3.3.1 Relative Humidity (RH%) Measurement
        2. 7.3.3.2 Temperature Measurement
      4. 7.3.4 NIST Traceability and Unique ID
      5. 7.3.5 Output Short Circuit Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 On-Chip Heater
        1. 7.4.1.1 Operating Principle
          1. 7.4.1.1.1 Heater Configuration Example
        2. 7.4.1.2 Heater Electrical Behavior
        3. 7.4.1.3 Heater Temperature Increase
        4. 7.4.1.4 Heater Usage Guidelines
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
    3. 8.3 Power Supply Recommendations
    4. 8.4 Rehydration Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
    6. 8.6 Storage and PCB Assembly
      1. 8.6.1 Storage and Handling
      2. 8.6.2 Product Storage
      3. 8.6.3 PCB Assembly Flow
      4. 8.6.4 Rework Consideration
      5. 8.6.5 Sensitivity to Chemicals and Vapors
      6. 8.6.6 Exposure to High Temperature and High Humidity Conditions
      7. 8.6.7 Recovering Sensor Performance: Bake and Rehydration Procedure
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.3.2 Temperature Measurement

The temperature in Celsius (°C) or Fahrenheit (°F) can be calculated from the VTEMP output voltage and the VDD using the following equations:

Equation 3. T℃=-66.875+218.75×VTEMPVDD=-45-17.50.8+1750.8×VTEMPVDD
Equation 4. T℉=-88.375+393.75×VTEMPVDD=-49-31.50.8+3150.8×VTEMPVDD

Figure 7-10 plots the calculated RH% as a function of normalized VTEMP/VDD:

HDC3120 HDC3120 Temperature Output ProfileFigure 7-10 HDC3120 Temperature Output Profile

Alternatively, to examine the voltage gain of the sensor for temperature measurements, the VTEMP voltage can also be expressed as a function of VDD and temperature in the following voltage sensitivity equation:

Equation 5. VTEMP=VDD×[T(℃)×4.571mV℃+0.306]
  • 4.571mV/°C represents the sensor gain which scales with VDD, showing voltage change per °C.
  • The voltage spans from 0.1 × VDD, the sensor offset at -45°C, to 0.9 × VDD , representing 130°C
Note:

The VTEMP output voltage rails out at temperature below -45°C (where the VTEMP= 0.1 × VDD), and temperature above 130°C (where the VTEMP= 0.9 × VDD).

Figure 7-11 illustrates the temperature output voltage as a function of temperature at different VDD levels. Figure 7-12 presents the same data, but with the temperature output voltage normalized to VDD.

HDC3120 Temperature Sensor Output (VTEMP) vs TemperatureFigure 7-11 Temperature Sensor Output (VTEMP) vs Temperature
HDC3120 Normalized Temperature Sensor Output (VTEMP) vs TemperatureFigure 7-12 Normalized Temperature Sensor Output (VTEMP) vs Temperature

Table 7-2 provides some examples of the VTEMP voltage reading at various temperature and VDD levels. Note even though the VTEMP voltage vary with VDD at the same temperature, VTEMP/VDD ratio remains constant, providing accurate measurements. This ratiometric design makes the sensor reading of the HDC3120 stable across supply variations.

Table 7-2 VTEMP Voltage at Various Temperature and VDD Levels
VDD = 1.8VVDD = 2.5VVDD = 3.3VVDD = 5.0VVTEMP/VDD Ratio
Temp= -40°C

0.221

0.3070.405

0.614

0.123
Temp= 0°C

0.550

0.764

1.009

1.529

0.306

Temp= 25°C

0.756

1.050

1.386

2.100

0.420

Temp= 85°C

1.250

1.735

2.291

3.471

0.694

Temp= 125°C

1.579

2.193

2.895

4.386

0.877

Sensor Gain8.229mV/°C11.429mV/°C15.085mV/°C22.857mV/°C
Sensor Offset550mV

764mV

1.009V

1.529V