For more information on board layout, refer to the related Precise temperature measurements with TMP116 and TMP117 (SNOA986) and Wearable temperature-sensing layout considerations optimized for thermal response (SNIA021) application reports on ti.com.
Place the power-supply bypass capacitor as close
as possible to the supply and ground pins. The recommended value of this bypass
capacitor is 0.1μF. In some cases, the pullup resistor can be the heat source,
therefore, maintain some distance between the resistor and the device.
- If the device is used to measure solid surface temperature:
- Use PCB with minimal thickness.
- Prevent PCB bending which can create a mechanical stress to package.
- Cover bottom of the PCB with copper plane.
- Remove bottom solder mask and cover exposed copper with gold layer if possible.
- Use thermal conductive paste between PCB and object surface.
- If PCB has unused internal layers, extend these layers under the sensor.
- Minimize amount of copper wires on top of the board.
- To minimize temperature “leakage” to surrounding air locate sensor in place with minimal air movement. Horizontal surfaces are preferable.
- To minimize temperature offset due to “leakage” to surrounding air cover sensor with thermo isolating foam, tape or at least cover with a stain.
- If the device is used to measure moving air temperature:
- Because moving air temperature usually has a lot of fluctuations the PCB increased thermal mass reduces measurement noise.
- Use a PCB with thicker copper layers if possible.
- Cover both side of unused board space with copper layer.
- Place PCB vertically along air flow.
- If the device is used to measure still air temperature:
- Miniaturize the board to reduce thermal mass. Smaller thermal mass results in faster thermal response.
- Remove the top solder mask.
- To prevent oxidation, cover any exposed copper with solder paste.
- Thermal isolation is required to avoid thermal coupling from heat source components through the PCB.
- Avoid running the copper plane underneath the temperature sensor.
- Maximize the air gap between the sensor and the surrounding copper areas (anti-etch), especially when close to the heat source.
- Create a PCB cutout between sensor and other circuits. Leave a narrow channel away from heat source components as a routing bridge into the island.
- If the heat source is top side, avoid running traces on top; instead, route all signals on the bottom side.
- Place the board vertically to improve air flow and to reduce dust collection.