ATSAM4S-WPIR-RD Atmel, ATSAM4S-WPIR-RD Datasheet - Page 22

• Manufacturer Part Number: ATSAM4S-WPIR-RD
• Description: Development Boards & Kits - ARM SAM4S16 W.PIR CAMERA REF. DESIGN
• Manufacturer: Atmel

Specifications of ATSAM4S-WPIR-RD

• Rohs: yes
• Product: Reference Designs
• Tool Is For Evaluation Of: ATSAM3S4BA
• Core: ARM Cortex M3
• Interface Type: JTAG, USB
• Operating Supply Voltage: 5 V
• Data Bus Width: 32 bit
• For Use With: RF231USB-RD

5.3.1
5.3.2
5.3.3
Analog GND routing
With the Atmel AT86RF231, consider pins 3, 6, 27, 30, 31 and 32 as analog ground pins, see
ground pins are to be routed to the paddle underneath the IC. The trace width has to be similar to the pad width when
connecting the pads, and increase, if possible, some distance from the pad.
Figure 5-5. Board layout – transceiver GND.
Each ground pin should be connected to the bottom plane with at least one via. Move the vias as close as possible. It is
always desired to integrate the single-pin ground connections into polygon structures after a short distance. Top,
bottom, and on multilayer boards, the inner ground planes, should be tied together with a grid of vias. When ground
loops are smaller than one tenth of the wavelength, it is safe to consider this as a solid piece of metal.
The soldering technology used allows the placement of small vias (0.15mm drill) within the ground paddle underneath
the chip. During reflow soldering, the vias get filled with solder, having a positive effect on the connection cross section.
The small drill size keeps solder losses within an acceptable limit. During the soldering process vias should be open on
the bottom side to allow enclosed air to expand.
Digital GND routing
With the Atmel AT86RF231, consider pins 7, 12, 16, 18 and 21 as digital ground pins.
Digital ground pins are not directly connected to the paddle. Digital ground pins may carry digital noise from I/O pad
cells or other digital processing units within the chip.
In case of a direct paddle connection, impedances of the paddle ground vias could cause a small voltage drop for this
noise and may result in an increased noise level transferred to the analog domain.
GND plane
Besides the function to provide supply ground to the individual parts, the ground plane has to be considered as a
counterpart for the antenna. Such an antenna base plate is considered as a continuous metal plane.
16
12
18
7
Atmel AVR2030: ATRF231USB – Hardware User Manual [APPLICATION NOTE]
6
21
3
32
31
30
27
Figure
42018A−AVR−08/2012
5-5. Analog
22