SNAS672A November   2015  – January 2016 HDC1080

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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 I2C Interface Electrical Characteristics
    7. 6.7 I2C Interface Timing Requirements
    8. 6.8 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Power Consumption
      2. 7.3.2 Voltage Supply Monitoring
      3. 7.3.3 Heater
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1 I2C Interface
        1. 7.5.1.1 Serial Bus Address
        2. 7.5.1.2 Read and Write Operations
        3. 7.5.1.3 Device Measurement Configuration
    6. 7.6 Register Map
      1. 7.6.1 Temperature Register
      2. 7.6.2 Humidity Register
      3. 7.6.3 Configuration Register
      4. 7.6.4 Serial Number Registers
      5. 7.6.5 Manufacturer ID Register
      6. 7.6.6 Device Register ID
  8. 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. 8.2.3 Application Curve
    3. 8.3 Implementation and Usage Recommendations
      1. 8.3.1 Soldering
      2. 8.3.2 Chemical Exposure and Sensor Protection
      3. 8.3.3 High Temperature and Humidity Exposure
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

An HVAC system thermostat control is based on environmental sensors and a micro-controller. The microcontroller acquires data from humidity sensors and temperature sensors and controls the heating/cooling system. The collected data are then shown on a display that can be easily controlled by the micro controller. Based on data from the humidity and temperature sensor, the heating/cooling system then maintains the environment at customer-defined preferred conditions.

8.2 Typical Application

In a battery-powered HVAC system thermostat, one of the key parameters in the selection of components is the power consumption. The HDC1080, with 1.3μA of current consumption (average consumption over 1s for RH and Temperature measurements), in conjunction with an MSP430, represents an excellent choice for low power consumption, which extends the battery life. A system block diagram of a battery powered thermostat is shown in Figure 15.

HDC1080 HVAC_TPL_snas672.gif Figure 15. Typical Application Schematic HVAC

8.2.1 Design Requirements

In order to correctly sense the ambient temperature and humidity, the HDC1080 should be positioned away from heat sources on the PCB. Generally, it should not be close to the LCD and battery. Moreover, to minimize any self-heating of the HDC1080 it is recommended to acquire at a maximum sample rate of 1sps (RH + Temp). In home systems, humidity and the temperature monitoring rates of less than 1sps (even 0.5sps or 0.2sps) can be still effective.

8.2.2 Detailed Design Procedure

When a circuit board layout is created from the schematic shown in Figure 15 a small circuit board is possible. The accuracy of a RH and temperature measurement depends on the sensor accuracy and the setup of the sensing system. The HDC1080 samples relative humidity and temperature in its immediate environment, it is therefore important that the local conditions at the sensor match the monitored environment. Use one or more openings in the physical cover of the thermostat to obtain a good airflow even in static conditions. Refer to the layout below ( Figure 18) for a PCB layout which minimizes the thermal mass of the PCB in the region of the HDC1080, which can improve measurement response time and accuracy.

8.2.3 Application Curve

The data shown below was acquired with the HDC1080EVM. A humidity chamber was used to control the environment.

HDC1080 D080_SNAS672.gif Figure 16. RH vs. Time

8.3 Implementation and Usage Recommendations

8.3.1 Soldering

When soldering the HDC1080 use the standard soldering profile IPC/JEDEC J-STD-020 with peak temperatures of 260 °C.

When soldering the HDC1080 it is mandatory to use no-clean solder paste and no board wash should be applied. The HDC1080 should be limited to a single IR reflow and no rework is recommended.

8.3.2 Chemical Exposure and Sensor Protection

The humidity sensor is not a standard IC and therefore should not be exposed to particulates or volatile chemicals such as solvents or other organic compounds. If any type of protective coating must be applied to the circuit board, the sensor must be protected during the coating process.

8.3.3 High Temperature and Humidity Exposure

Long exposure outside the recommended operating conditions may temporarily offset the RH output. Table 10 shows the RH offset values that can be expected for exposure to 85 °C and 85 % RH for durations between 12 and 500 hours (continuous).

Table 10. Induced RH Offset Due to Extended Exposure to High Humidity and High Temperature (85°C/85% RH)

85°C/85% RH Duration (hours) 12 24 168 500
RH Offset (%) 3 6 12 15

When the sensor is exposed to less severe conditions, Figure 17 shows the typical RH offset at other combinations of temperature and RH.

HDC1080 RH_vs_temp_diagram_snas672.gif Figure 17. Relative Humidity Accuracy vs Temperature