ATSAM4S-WPIR-RD Atmel, ATSAM4S-WPIR-RD Datasheet - Page 21

• 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

5.2
5.3
The Atmel AT86RF231 antenna port should be connected to a 100Ω load with a small series inductance of 1nH to 2nH.
This is achieved with the connection fan out in between the IC pins and the filter balun balanced feed pins (B1 pads 3
and 4). The trace width is kept small at 0.2mm for a length of approximately 1.5mm. The dashed area in
a midlayer cutout inside the PCB layout. The bottom layer is implemented as ground plane. Therefore, the distributed
capacitance between top and bottom is low, and transmission lines are rather inductive.
PCB detail 2 – crystal routing
Figure 5-4
keep any radiation of 16.000MHz harmonics low.
The reference crystal Q2 and load capacitors C20/21 form the resonator circuit. These capacitors are to be placed close
to the crystal.
The shielded board design ensures immunity against external impairments such as burst and surge. Additionally the
crystal housing is connected to ground. The crystal signal lines should be embedded within ground areas to protect
against board internal crosstalk. This design rule had to be ignored due to the USB stick space constraints.
If possible, the ground connection in between the capacitors should be the crystal housing contact too, resulting in a
robust and stable resonator. The resonator block is enclosed within ground traces around it and a plane on the bottom
side. Do not connect the resonator directly to the plane beneath the block.
Figure 5-4. Board layout – XTAL section.
PCB detail 3 – ground plane routing and feed line design
The following sections provide details about analog and digital ground routing, the ground plane and the RF
transmission line.
shows the reference crystal PCB area which requires optimization to minimize external interference and to
Atmel AVR2030: ATRF231USB – Hardware User Manual [APPLICATION NOTE]
42018A−AVR−08/2012
Figure 5-3
has
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