Hi,
I am planning to use TMP007 IR sensor for skin temp measurement.
I will be using metal shielding for defining FOV for the sensor as target object dimension is very small.
As per design guidelines specified in TMP007 Layout and Assembly Guide, section5, for metal shield height of 1mm and thickness of 0.2mm, diameter of aperture differs based on the required FOV. For ex- for 118Degree FOV, required aperture radius is 1.25mm, this implies to minimum width of shield is 2.5mm. Here my aim is to have pcb size of 2.5mmX2.5mm.
So my questions are;
1. If I choose a metal shield height of 0.625mm, max height of the 8-pin DSBGA package, then effective distance of shield from the base of sensor is 0.625mm - 0.25mm = 0.375. At 0.375mm distance, to have an FOV of 118Degree, we require an aperture radius of 0.516mm. With this shield width can go to minimum of 1.032mm. Do you see any problem with this shielding arrangement on the performance of TMP007 sensor. Please note that in this arrangement there is no air gap between IC top and metal shield.
2. Another approach is if I increase the radius of aperture to 1.25mm and shield height is adjusted to 1mm, we will meet 118degree FOV theoretically. As we know the absorber size is 330umX330um, however aperture diameter is 2.5mm which is larger compared to absorber size. That means although we set FOV of 118degree, but effective IR energy absorbed by the IR element is not 100%. In this case majority of IR energy will fall on whole IC and the PCB. In this case then how does this metal shielding improve the temperature measurement? Please correct me if my understanding is not proper.
3. As I learnt that the metal shield is implemented and tested in TI facility. Do we get that test setup arrangement to understand the concept and implement in our design? I am based in Bangalore India, so could you please help us in having demo of the test setup with metal shield arrangement?
Best Regards,
Rajesh Kumar
