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.
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 5 kΩ. In some applications, the pullup resistor can be lower or higher than 5 kΩ. 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 should be connected directly to GND, VDD, or left open for address selection of four possible unique target ID addresses per the addressing scheme Table 8-2. The ALERT output pin can be connected to a microcontroller interrupt that triggers an event that occurred when the relative humidity and/or temperature limit exceeds the programmed value. The ALERT pin should be left floating when not in use.