This document provides the design guidelines of a 4-layer PCB board, for the CC31xx and CC32xx
SimpleLink™ Wi-Fi®family of devices. The CC31xx and CC32xx are easy to lay-out, QFN-packaged
devices. Optimize the board’s performance by following these suggestions during the board’s design. The
first section is a brief overview of the SimpleLink Wi-Fi family of devices. The second section focuses on
the PCB specification; the third section addresses components placement, and board layer information.
The last section, on layout guidelines, covers the board’s main sections such as RF, power, clock, digital
I/O, and the ground. Each section can be read independently.
In addition to this document, TI recommends verifying the schematic board design with the associated
schematic checklist.
1Trademarks
SimpleLink, Internet-on-a-chip, E2E are trademarks of Texas Instruments.
ARM, Cortex are registered trademarks of ARM Limited.
Wi-Fi is a registered trademark of Wi-Fi Alliance.
All other trademarks are the property of their respective owners.
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layout Guidelines
Start the design with the industry’s first Internet-on-a-chip™. Created for the Internet of Things (IoT), the
SimpleLink Wi-Fi family has several variants. The CC3100 SimpleLink Wi-Fi and IoT solution dramatically
simplifies the implementation of Internet connectivity. This product integrates all protocols for Wi-Fi and
Internet, which greatly minimizes host microcontroller (MCU) software requirements. CC3200 device is a
wireless MCU that integrates a high-performance ARM®Cortex®-M4 MCU with the CC3100 network
processor subsystem, allowing customers to develop an entire application with a single IC. With on-chip
Wi-Fi, Internet, and robust security protocols, no prior Wi-Fi experience is needed for faster development.
SimpleLink Wi-Fi is a complete platform solution, including various tools and software, sample
applications, user and programming guides, reference designs, and the TI E2E™ support community. The
devices are available in an easy to lay-out QFN package. The layout for both devices are similar, with a
higher number of IOs routed for the CC3200.
3PCB Specification
3.1PCB Stack-Up
An example stack-up is shown in Figure 1, used for the construction of the CC3100BOOST Rev3.3-A. The
user can alter the layer stack-up based on their requirements, but the impedance of the 50-Ω lines should
be recalculated. Having the L1-L2 distance reduced helps improve the grounding and the RF decoupling.
TI recommends keeping the L1-L2 distance similar to the recommended value.
CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layout Guidelines
5
PCB Specification
3.2PCB Design Rules
ParameterValueComments
Number of layers4
Thickness1.1 mm ±
Size of PCB2.0” x 1.7”
Solder maskRedCan be replaced with any color
DielectricFR4
SilkWhiteCan be replaced with any color
Surface finishENIG
Min track width6 milsMin track width can be reduced but cost would be higher
Min spacing6 milsMin spacing can be reduced but the cost would be higher
Mid drill diameter8 mils12-mil diameter drill is used on the Rev 3.3-A board
Copper thickness1 oz
Lead free / ROHSYes
Impedance controlYes50-Ω controlled impedance trace of 18-mils width on L1 w.r.t L2 (GND).
Impedance variation5%
www.ti.com
Table 1. PCB Design Rules
For greater thickness increase the distance between L2 and L3
10%
Air gap = 15 mils
Note: The above calculations are based on CPW-G (NOT microstrip).
3.3Layer Information
The 4-layer PCB is used with the configuration, as shown in Table 2.
Layer UsageNotes
1Signal + RFRF trace is a CPW on L1 w.r.t. L2 ground
2GNDReference plane for RF
3Power + signalThe power planes for the power amplifier (PA), analog blocks and the main input supply are routed on
4Power + signal
Table 2. 4 Layer PCB
this layer
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layout Guidelines
The complete layout package is available for download on the TI website at http://www.ti.com/tool/cc3200-
launchxl-rd and http://www.ti.com/tool/cc3100boost-rd. TI recommends that the customers copy the exact
layout of the engine area to ensure optimum performance as measured on the CC3x00 reference boards.
4.1Placement of Components
The components placement on the CC3100 BoosterPack is provided in Figure 2. This placement provides
optimum performance of the device. Great care must be taken for the power inductors components to
ensure reduced emissions and optimum EVM and mask performance. The power inductors should be
placed close to the device, and the power traces should be minimized. The CC3x00 device is sensitive to
the layout of the DC-DC converter, which can impact the performance of the device. For the main
inductors at the analog, power amplifier, and digital DC-DC output, see Table 3.
Most of the routing is performed on Layer-1 to avoid vias on the board (see Figure 3). The trace widths
are maximized for high-current pins and minimized for signal pins. For example, the signal pins can be
routed with 6 mils (4 mils, if possible) and the power pins with 12 mils and above.
www.ti.com
Figure 3. Layer-1
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layout Guidelines
Layer-2 is primary ground plane for the board reference (see Figure 4). It has a void for the antenna
section, which is per the antenna guidelines. This return current path for the input de-coupling capacitors
(C11, C13, and C18) is routed on L2 using thick traces to isolate RF ground from a noisy supply ground.
This is also required to meet the IEEE spectral mask specifications.
Layout Information
Figure 4. Layer-2
SWRU370B–June 2014–Revised August 2018
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layer-3 is used to route the power lines to the device (see Figure 5). Power planes are necessary for the
power amplifier (PA) and the main supply input to the device. More details are available in subsequent
sections.
www.ti.com
Figure 5. Layer-3
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layout Guidelines
Layer-4 is used for routing the power and the signal lines on the board (see Figure 6). It is also the main
power dissipation GND layer for the QFN package. The bottom GND plane must be maximized for the
best thermal performance. The solder mask has been kept open below the QFN device to improve heat
dissipation and yield.
Layout Information
Figure 6. Layer-4
SWRU370B–June 2014–Revised August 2018
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
As a wireless device, the RF section gets the top priority in terms of layout (see Figure 7). It is very
important for the RF section to be laid out correctly to get the optimum performance from the device. A
poor layout can cause performance degradation for the output power, the error vector magnitude (EVM),
the sensitivity, and the spectral mask.
www.ti.com
Figure 7. RF Section Layout
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layout Guidelines
The antenna is the element used to convert the guided waves on the PCB traces to the free-space
electromagnetic radiation. The placement and layout of the antenna is key to increased range and data
rates.
The guidelines in Table 4 must be observed for the antenna.
Sr No Guidelines
1Place the antenna on an edge or corner of the PCB.
2Ensure that no signals are routed across the antenna elements on all the layers of the PCB.
3Most antennas, including the chip antenna used on the BoosterPack, require ground clearance on all the layers of the
PCB. Ensure that the ground is cleared on the inner layers as well.
4Ensure that there is provision to place matching components for the antenna. These must be tuned for best return loss
once the complete board is assembled.
Any plastics or casing should also be mounted while tuning the antenna, as this can impact the impedance.
5Ensure that the antenna impedance is 50 Ω, as the device is rated to work only with a 50-Ω system.
6In case of printed antenna, ensure that the simulation is performed with the solder mask in consideration.
7Ensure that the antenna has a near omni-directional pattern.
8The return loss measured at the filter out (looking into the device) should be better than -10 dB. To ease the FCC, CE, and
ETSI certification, the antenna used should be of the same gain or lesser.
Table 5. Recommended Components
Layout Guidelines
Table 4. Antenna Guidelines
Choice Part NumberManufacturerNotes
1AH316M245001-TTaiyo YudenCan be placed on the edge of the PCB and uses less PCB space
2RFANT5220110A2TWalsimMust be placed on the corner of the PCB
Table 6. Characteristic of Recommended Antenna
ParameterSpec
Frequency bandwidth2.4G to 2.5G
Typical peak gain+1.9 dBi
Average gain at OMNI plane0 dBi
Efficiency (typical)–1.3 dB (73%)
VSWR3
5.1.2Filter Placement and Routing
The RF filter used on the board performs the important function of attenuating the out-of-band emissions
from the device. The recommended filter is DEA202450BT-1294C1. The datasheet for the filter can be
accessed at http://www.tdk.co.jp/tefe02/rf_bpf_dea202450bt-1294c1-h_en.pdf.
SWRU370B–June 2014–Revised August 2018
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
The RF signal from the device is routed to the antenna using a coplanar waveguide with ground (CPW-G)
structure. This structure offers the maximum isolation across filter gap and the best possible shielding to
the RF lines. In addition to the ground on the L1 layer, placing GND vias along the line also provides
additional shielding.
Layout Guidelines
Table 8. Characteristic of Recommended Filter
800-83030 dB (min)
1600-167020 dB (min)
3200-330030 dB (min)
4000-415045 dB (min)
4800-500020 dB (min)
5600- 580020 dB (min)
6400-660020 dB (min)
7200-750035 dB (min)
7500-1000020 dB (min)
Figure 9. Coplanar Waveguide (Cross Section) With GND and via Stitching
Figure 10. CPW With GND (Top View)
SWRU370B–June 2014–Revised August 2018
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
The recommended values for the PCB are provided in Table 9.
(1)
Er is assumed to be of an FR-4 substrate.
5.2Power
•All of the input de-coupling capacitors (C11, C13, and C18) should be routed on L2 using thick traces
to isolate RF ground from a noisy supply ground. This is also required to meet the IEEE spectral mask
specifications.
•Maintain the thickness of power traces to be higher than 12 mils. Special care should be taken for
power amplifier supply lines (pin 33, 40, 41, and 42) and all input supply pins (pin 37, 39, and 44).
•Place all de-coupling capacitors as close as possible to the respective pins.
•Power budget: The CC3X00 device can consume up to 450 mA for 3.3 V, 670 mA for 2.1 V, and 700
mA for 1.85 V for 24 msec during the calibration cycle. Ensure that the power supply is designed to
source this current without any issues. The complete calibration (TX and RX) can take up to 17 mJ of
energy from the battery over a time of 24 ms.
•There are many high-current input pins on the CC3X00 device. Ensure the trace feeding these pins is
capable of handling the following currents:
– PA DCDC input : pin 39. Max 1A
– ANA DCDC input : pin 37 : Max 600 mA
– Dig DCDC input : pin 44: Max 500 mA
– PA DCDC switching nodes : pin 40/41 , Max 1A
– PA DCDC output node: pin 42, Max 1A
– ANA DCDC switching node: pin 38: Max 600 mA
– Dig DCDC switching node: pin 43 : Max 500 mA
– PA supply : pin 33: Max 500mA
Table 9. Recommended Values for the PCB
ParameterValueUnits
W18mils
S15mils
H10mils
(1)
Er
3.9
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5.2.1Inductors for Power Management
The components used in the power management section of the design are critical to achieve the required
performance. These should be chosen based on the recommendations in Table 10.
InductorsValueESR
PA DC-DC1 uHTBD1.5TBD20%
ANA, DIG DC-DC2.2 uHTBD1.3TBD20%
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layout Guidelines
The 32.768K XTAL should be placed close to the QFN package. Ensure the load capacitance is tuned
based on board parasitic, so that the frequency tolerance is within ±150 ppm.
Tolerance with temperature and aging±150 ppm
5.3.240M XTAL
The 40M XTAL should be placed close to the QFN package. Ensure the load capacitance is tuned based
on board parasitic, so that the frequency tolerance is within ±20 ppm. The frequency tolerance for the
XTAL across temperature and with aging should be ±25 ppm. In addition, ensure no high frequency lines
are routed closer to the XTAL routing, to avoid any phase noise degradation.
Tolerance with temperature and aging±25 ppm
Layout Guidelines
Table 11. Characteristic of Recommended 32K XTAL
ParameterSpec
Nominal frequency32.768 kHz
Table 12. Characteristic of Recommended 40M XTAL
ParameterSpec
Nominal frequency40 MHz
Tolerance±20 ppm
Load capacitance8 pF
5.4Digital I/O
Route serial peripheral interface (SPI) and universal asynchronous receiver/transmitter (UART) lines away
from any RF traces, as these digital I/O lines are high-frequency lines and can cause interference to the
RF signal.
Keep the length of the high-speed lines as short as possible to avoid transmission line effects. Keep the
line lower than 1/10th of the rise time of the signal to ignore transmission line effects. This is required only
if the traces cannot be kept short. The resistor should be placed at the source end, closer to the device
driving the signal.
Add series-terminating resistors for each high-speed line (for example, SPI_CLK, SPI_DATA) to match the
driver impedance to the line. Typical terminating resistor values range from 27 to 36 Ω for a 50-Ω line
impedance.
Route high-speed lines with a ground reference plane continuously below it to offer good impedance
throughout, and help shield the trace against EMI interference.
Avoid stubs on high speed lines to minimize the reflections. If the line needs to be routed to multiple
locations, use a separate line driver for each line.
If the lines are longer compared to the rise time, add series-terminating resistors near the driver for each
high-speed line (for example, SPI_CLK, SPI_DATA) to match the driver impedance to the line. Typical
terminating resistor values range from 27 to 36 Ω for a 50-Ω line impedance.
SWRU370B–June 2014–Revised August 2018
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
1. Ensure 7x7 ground vias are placed on the ground pad for optimal thermal dissipation (see Figure 11).
The via drill size can be between 8 mils to 12 mils.
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Figure 11. 7x7 Ground Vias on Ground Pad
2. Open the solder mask on L4 for better soldering yield.
3. Split solder paste into smaller blocks (see Figure 12) to avoid component lifting while soldering or reflow.
Figure 12. Split Solder Paste Into Smaller Blocks
4. Solder paste should cover at-least 75% of the ground tab of the QFN.
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layout Guidelines
This document presents an introduction to designing a 4-layer PCB board for the CC3100/CC3200
SimpleLink Wi-Fi easy-to-layout QFN packaged family of devices. In addition to the recommendations
presented here, see the CC3100 SimpleLink Wi-Fi and IoT Solution BoosterPack design files located at
http://www.ti.com/lit/zip/swrc288 and the CC3200 SimpleLink Wi-Fi and IoT Solution With MCU
LaunchPad board design files located at http://www.ti.com/lit/zip/swrc289.
7Additional References
1. CC31xx and CC32xx main landing page.
2. The CC3100 SimpleLink™ Wi-Fi® and IoT Solution for MCU Applications data sheet (SWAS031)
3. The CC3200 SimpleLink™ Wi-Fi® and IoT Solution, a Single Chip Wireless MCU data sheet
(SWAS032)
www.ti.com
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CC3100 and CC3200 SimpleLink™ Wi-Fi®and Internet of Things Solution
Layout Guidelines
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