STM32W108B-SK STMicroelectronics, STM32W108B-SK Datasheet - Page 6

• Manufacturer Part Number: STM32W108B-SK
• Description: STARTER KIT FOR STM32W108
• Manufacturer: STMicroelectronics
• Series: STM32r
• Type: MCUr

Specifications of STM32W108B-SK

• Featured Product: STM32 Cortex-M3 Companion Products
• Contents: Board
• Silicon Manufacturer: ST Micro
• Core Architecture: ARM
• Core Sub-architecture: Cortex - M3
• Silicon Core Number: STM32
• Silicon Family Name: STM32W108xx
• Kit Contents: Board
• Features: IEEE
• Mfg Application Notes: STM32W108 Adjacent Channel Rejection Measurements
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: *
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Reference design
6/14
To minimize network loss, the matching topology should try to keep Smith chart loci towards
the center of the Smith chart. To do that, the following impedance transformation options are
available:
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●
●
●
PCB parasitic elements play a part in the impedance transformation and even with the
tightest of layouts, traces between the matching elements will add significant reactance at
2.4 GHz. In particular, there will be some series inductance between the package pins and
the first matching element. This is significant when that element is shunted because it
cannot be absorbed into that reactance. Since this effect cannot be avoided, it is best to take
advantage of it.
The option with the lowest loss and least complex arrangement is series inductance
followed by shunt inductance. To make use of the PCB traces, it must be recognized that
they operate more like transmission lines which travel slightly differently on the Smith chart
compared with real inductors and this affects the shunt inductance value.
Traces of 100Ω which equate to 150um wide on a 0.4mm thick FR-4 substrate should be
used. In ST's simple single-ended representation in the Smith chart, the balanced pair must
be modeled as a single 200Ω transmission line.
transformation.
Series inductance followed by Shunt capacitance
–
–
–
Series inductance followed by Shunt inductance
–
–
Shunt inductance followed by series capacitance
–
Shunt inductance followed by Series inductance
–
–
This option favors lower balun ratios.
It leads to comparatively large inductance values.
It requires either long PCB traces or two discrete inductors (balanced network)
which means inductor Q becomes an issue.
Similar to auto-transformer action.
Sweet-spot for 100Ω balun if series inductance fabricated from PCB traces since
neither too long nor too short.
Not allowed because DC feed to PA is required from balun centre-tap.
Favors lower balun ratios, but even at 1:1 the required series inductance is
comparatively large.
It requires either long PCB traces or two discrete inductors (balanced network)
which means inductor Q becomes an issue.
Doc ID 17406 Rev 3
Figure 3
illustrates the impedance
AN3206