Datasheet

ATBTLC1000 Hardware Design Guidelines – Ultra Low Power BLE 4.1 SoC [USER GUIDE]
Atmel-42537B-ATBTLC1000-Hardware-Design-Guidelines_UserGuide_102015
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Placement of FB1, C12, and C16 should be as close as possible to the VBAT_BUCK pin (pin 15), with the
smaller capacitor, C16, placed closest to the pin. Again, the route should be as heavy as possible to
provide a low impedance path. The placement and routing of these components is shown in Figure 3-2.
Note that the PMU is a switching regulator and produces noise within the 2.4GHz receive band. Therefore
it is essential that the RF route, components, and antenna be kept as far away from the PMU and its
components (L5, L6, and C14) as possible.
The same goes for the VBAT_Buck supply. This is the supply for the PMU and noise from the PMU feeds
back to this supply pin. FB1 is used to suppress this noise to keep it from radiating from the supply route.
Therefore, the RF route should also be kept away from the VBAT_Buck supply route and FB1, C12, and
C16.
A shield should be placed over the ATBTLC1000 and PMU components to keep any RF radiation from
being picked up by the antenna.
3.4 Ground
Proper grounding is essential for correct operation of the device and peak performance. A solid inner layer
ground plane should be provided. The center ground paddle of the device must have a grid of ground vias
solidly connecting the pad to the inner layer ground plane. A 3x3 grid of ground vias is recommended.
These ground vias must surround the perimeter of the pad. One of these ground vias must be in the
center pad as close as possible to pin 2 (RFIO). This ground via serves as the RF ground return. There
must also be a ground via in the center pad as close as possible to pin 14. This is the ground return for
the PMU. See Figure 3-4 for an example of the recommended grounding of the center pad.
Figure 3-4. Proper Grounding of Center Ground Pad
As mentioned previously, one inner layer should be dedicated as a ground plane. It is important that the
ground return currents have direct low impedance path back to the device ground. This is especially
crucial for the RF and PMU ground returns. Figure 3-5 shows the top layer RF path route superimposed
over an example of an incorrect second layer ground. In Figure 3-5 the top layer is shown in green and
the second layer is shown in red. The RF route is indicated by the blue line. The RF return current will flow
back along this path to the package ground pin closest to the RFIO pin (pin 2). But as shown in Figure 3-