To improve measurement accuracy, TI recommends to isolate the HDC302x from all heat sources in the form of active circuitry, batteries, displays and resistive elements. If design space is a constraint, cutouts surrounding the device or the inclusion of small trenches can help minimize heat transfer from PCB heat sources to the HDC302x. To avoid self-heating the HDC302x, TI recommends to configure the device to no faster than 1 measurement/second. Avoid adding heat to the device from hot sources like radiators or the sun.

The HDC302x operates only as a target device and communicates with the host through the I2C-compatible serial interface. SCL is an input pin, SDA is a bidirectional pin, and ALERT is an output. The HDC302x requires a pullup resistor on the SDA. An SCL pullup resistor is required if the system microprocessor SCL pin is open-drain. The recommended value for the pullup resistors is generally 5 kΩ. In some applications, the pullup resistor can be lower or higher than 5 kΩ. The size of the pullup resistor is determined by the amount of capacitance on the I2C lines, bus leakage, and the communication frequency. For further details, see the I²C Pullup Resistor Calculation application note. A 0.1-µF bypass capacitor is recommended to be connected between V+ and GND. Use a ceramic capacitor type with a temperature rating that matches the operating range of the application, and place the capacitor as close as possible to the VDD pin of the HDC302x. The ADDR and ADDR0 pins must be connected directly to GND or VDD for address selection of four possible unique target ID addresses per the addressing scheme (see Table 7-2). The ALERT output pin can be connected to a microcontroller interrupt that triggers an event that occurred when the relative humidity or temperature are outside the programmed limits. Keep the ALERT pin in/out current below 1mA to prevent the device from self-heating. The ALERT pin must be left floating when not in use. If not used, connecting the nRESET pin to VDD is best. This is to avoid glitches on the nRESET pin that can be caused by electromagnetic interference.

The user can decide whether or not to solder the package thermal pad to the PCB. Not soldering the thermal pad helps minimize thermal mass for maximum heater efficiency or to best measure ambient temperature (this also gives the device the best chance to survive a short caused by water getting under the package due to condensation). Soldering the thermal pad aids in the stability of the RH measurements because the temperature measurements are more stable due to the increased thermal mass. When using the HDC302x in a condensing environment, using the HDC3022 is best, since the IP67-rated filter cover keeps the sensor safe from water ingress. Users must also take caution to verify that water does not get under the device and on the pins of the device, to avoid shorting.