Data Sheet

WL1801MOD,
WL1805MO
D
,
WL1831MO
D
,
WL1835MOD
SWRS152M – JULY 2013 – REVISED OCTOBER 2017
www.ti.com
34 Applications, Implementation, and Layout
Copyright © 2013–2017, Texas Instruments Incorporated
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Product Folder Links: WL1801MOD WL1805MOD WL1831MOD
WL1835MOD
Table 7-2. Layout Recommendations Summary (continued)
ITEM
DESCRIPTION
Supply and Interface
14 The power trace for V
BAT
must be at least 40-mil wide.
15 The 1.8-V trace must be at least 18-mil wide.
16 Make VBAT traces as wide as possible to ensure reduced inductance and trace resistance.
17 If possible, shield V
BAT
traces with ground above, below, and beside the traces.
18 SDIO signals traces (CLK, CMD, D0, D1, D2, and D3) must be routed in parallel to each other and as short as possible (less than
12 cm). In addition, every trace length must be the same as the others. There should be enough space between traces – greater
than 1.5 times the trace width or ground – to ensure signal quality, especially for the SDIO_CLK trace. Remember to keep these
traces away from the other digital or analog signal traces. TI recommends adding ground shielding around these buses.
19
SDIO and digital clock signals are a source of noise. Keep the traces of these signals as short as possible. If possible, maintain a
clearance around them.
7.1.3 RF Trace and Antenna Layout Recommendations
Figure 7-2 shows the location of the antenna on the WL1835MODCOM8B board as well as the RF trace
routing from the WL1835 module (TI reference design). The Pulse multilayer antennas are mounted on
the board with a specific layout and matching circuit for the radiation test conducted in FCC, CE, and IC
certifications.
NOTE
At least an equivalent 1dB loss (in the form of trace, cable or 1-dB pi-pad loss) is
required between the output of the WL18MODGB module and the antenna to be
compliant with the current Z64-WL18SBMOD and 451I-WL18SBMOD module
certification.
Antennas are orthogonal
to each other.
Antennas distance is Higher than
half wavelength.
76.00mm
No sharp corners.
Constant 50 OHM control
impedance RF Trace.
Antenna placement on
the edge of the board.
Figure 7-2. Location of Antenna and RF Trace Routing on the WL1835MODCOM8B Board
Follow these RF trace routing recommendations:
• RF traces must have 50-Ω impedance.
• RF traces must not have sharp corners.
• RF traces must have via stitching on the ground plane beside the RF trace on both sides.
• RF traces must be as short as possible. The antenna, RF traces, and module must be on the edge of
the PCB product in consideration of the product enclosure material and proximity.