Proper PCB layout of the HDC302x-Q1 is critical to obtaining accurate measurements of temperature and relative humidity. Therefore, TI recommends to:
- Isolate all heat sources from the HDC302x-Q1. This design means positioning the HDC302x-Q1 away from power intensive board components such as a battery, display, or microcontroller. Ideally, the only onboard component close to the HDC302x-Q1 is the supply bypass capacitor. See the Layout Example for more information.
- Eliminate copper layers below the device (GND, VDD).
- Use slots or a cutout around the device to reduce the thermal mass and obtain a quicker response time to sudden environmental changes.
The diameter of the routing in Layout Example is 6mm. While this sizing is not important, it is important to ensure sufficient isolation of external thermal gradients present on the PCB. Other representations of cutouts for thermal relief, as well as additional information can be found in the Optimizing Placement and Routing for Humidity Sensors application note.
- Follow the Example Board Layout and Example Stencil Design that is illustrated in Mechanical, Packaging, and Orderable Information.
- The SCL and the SDA lines require pullup resistors and TI recommends to connect a 0.1-uF capacitor to the VDD line.
- TI recommends a multilayer ceramic bypass X7R capacitor of 0.1 μF between the VDD and GND pins.
- Soldering the package thermal pad to a board pad that is left floating is best practice. However the package thermal pad can be left floating to minimize thermal leakage for maximum heater efficiency. See the HDC3x Silicon User's Guide for more information regarding when leaving the thermal pad floating can be helpful for the user application.