AC530 Fastrax, AC530 Datasheet - Page 28

• Manufacturer Part Number: AC530
• Description: GPS Development Tools Application Board for UC530
• Manufacturer: Fastrax

Specifications of AC530

• Rohs: yes
• Product: Application Boards
• Tool Is For Evaluation Of: UC530
• Frequency: 1.575 GHz
• Operating Supply Voltage: 3.3 V
• Interface Type: UART
• Description/function: Fastrax Application Board AC530 provides the UC530 connectivity to the Fastrax Evaluation Kit or to other evaluation purposes
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Operating Supply Current: 25 mA

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For a multi-layer PCB the inner layers below the UC530 is suggested to be dedicated signal traces and copper plane
for the rest of the area. It is always better to route very long signal traces in the inner layers of the PCB. In this way
the trace can be easily shielded with ground areas from above and below.
The serial resistors at the I/O should be placed as close to the UC530 module as possible. In this way the risk for
the EMI leakage is minimized. For the same reason by-pass supply capacitors should be connected very close to
the module with short traces to IO contacts and to the ground plane. Place a GND via hole as close as possible to
the capacitor.
Connect the GND soldering pads of the UC530 to ground plane with short traces (thermals) to via holes, which are
connected to the ground plane. Use preferably one via hole for each GND pad.
A RF signal is suggested to be routed clearly away from other signals between two ground planes as a Stripline
Transmission Line; this minimizes the possibility of interference and coupling. The proper width for the 50 ohm
transmission line impedance depends on the dielectric material of the substrate, width of the signal trace and the
height (separation) of the two ground planes. With FR-4 material the width of the trace shall be about 30% of the
ground plane height. E.g. 0.4mm ground plane height results to 0.15mm trace width with FR-4 substrate.
Figure 14 Stripline transmission line
Any board space free of signal traces should be covered with copper areas connected to ground net; in this way a
solid RF ground plane is achieved throughout the circuit board. Several via holes should be used to connect the
ground areas between different layers.
Additionally, it is important that the PCB build-up is symmetrical on both sides of the PCB core. This can be
achieved by choosing identical copper content on each layers, and adding copper areas to route-free areas. If the
circuit board is heavily asymmetric, the board may bend (wrap) during the PCB manufacturing or reflow soldering.
Bending and wrapping may cause soldering failures and reduce end product reliability.
The AC530 Application Board layout described in next chapter can be also used as layout reference
implementation.
7.3.1 Other electronics on mother board
Signal traces on top and bottom layers should have minimum length. Route signals mainly at inner layers below
the top or bottom ground plane. In this way, a solid RF ground is achieved throughout the circuit board on top and
bottom sides. Several via holes should be used to connect the ground areas between different layers.
Areas with dense component placing and dense routing requirements should be covered with a metal shield,
which should be connected to ground plane with multiple GND via holes. Small ground plane openings for SMT
components (length few mm, like LED or push buttons) in the ground plane are OK without a shield.
Dense areas having multiple via holes may open the ground plane for wide areas, thus blind and buried via holes
are suggested to be used when changing layers for internal signals and power planes.
2012-05-03
UC530_Datasheet