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Silicon Laboratories EFR32 1 Series, Руководство по проектированию оформления

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The ideal layer consistency for PCBs with more than two layers is as follows:

Top layer:

Use as much continuous solid GND metallization as possible with many vias.

First inner layer:

Use continuous, unified GND metallization beneath the RF part; wires can be routed beneath the non-
RF parts if necessary.

All other inner layers:

Route as many (supply and digital) traces on these layers as possible.

Bottom layer:

This layer should be unified GND metal; route traces on this layer only if necessary.

The following figure illustrates layer consistency on the layout of the EFR32 Series 1 Dual-band Reference Radio Board.

Top

Inner 1

Inner 2

Bottom

Figure 2.5.  Layer Consistency on the Layout of the EFR32 Series 1 Dual-band Reference Radio Board

Note: 

The  sub-GHz  matching  has  some  special  layout  recommendations  for  the  individual  PCB  layers,  which  will  be  discussed  in

2.2.1 Layout Design Guidelines (sub-GHz)

.

 

• Route traces (especially the supply and digital lines) on inner layers for boards with more than two layers.
• Avoid placing the supply lines close to the PCB edge.
• To reduce sensitivity to PCB thickness variations, use 50 Ω grounded coplanar lines where possible for connecting the antenna or

the U.FL connector to the matching network. This also reduces radiation and coupling effects. A general rule is to use 50 Ω trans-
mission lines where the length of the RF trace is longer than λ/16 at the fundamental frequency.

• The interconnections between elements are not considered transmission lines since their lengths are much shorter than the wave-

length, and, thus, their impedances are not critical. As a result, their recommended width is equal to the width of the pad of the ap-
plied components. In this way, reflections at pad-trace transitions can be prevented, and parasitic capacitances to ground can be
minimized. Examples for the trace dimensions are shown in the table below.

• Use many vias near the coplanar lines in order to minimize radiation.

AN928.1: EFR32 Series 1 Layout Design Guide

Guidelines for Layout Design When Using EFR32 Wireless MCUs

silabs.com

 | Building a more connected world.

Rev. 0.5  |  9

Содержание EFR32 1 Series

Страница 1: ...d debug environment In order to take advantage of the capabilities and features on custom hardware Silicon Labs recommends including debugging and programming interface connector s in custom hardware designs The details and ben efits of including these connector interfaces are detailed in AN958 Debugging and Pro gramming Interfaces for Custom Designs The power configurations and the proper usage o...

Страница 2: ... and it is strongly recommended to use the same framed RF layout in order to avoid any possibility of detuning effects The figure below shows the framed compact RF part of the designs Figure 1 1 Top Layer of the Radio Board Left Side and Assembly Drawing of the RF Part Right Side The layout of the MCU VDD filtering capacitors should also be copied from the reference design as much as possible When...

Страница 3: ... of harmonic signals Since most regulatory standards e g FCC ETSI ARIB etc require the harmonic signals to be attenu ated below some absolute power level in watts or dBm the amount of low pass filtering required is generally greater on an RF radio board using an EFR32 that was designed for higher output power In the figure above there is an additional component R1 beside the 4 element matching whi...

Страница 4: ...he correct matching network information refer to the datasheet and reference designs The sub GHz EFR32 Series 1 wireless MCU can provide maximum 19 5 dBm power All sub GHz EFR32 matching network consist of the following sections impedance transformation circuit differential to single ended balun and low pass filter For further details on the sub GHz matching network principles refer to the applica...

Страница 5: ... sitic caps to the ground However couplings between neighbor discretes may increase in this way To reduce the coupling between the nearby discrete inductors avoid placing them in the same orientation Use tapered line between transmission lines with different width i e different impedance to reduce internal reflections Avoid using loops and long wires to obviate their resonances They also work well...

Страница 6: ...practices should be applied with a 2 element matching network as well Most of the layout guidelines in this section are general and should be applied in the sub GHz layout design as well The layout structure for the RF part of the EFR32 Series 1 Dual band Reference Radio Board is shown in the figure below the 2 4 GHz matching is highlighted by a blue frame Figure 2 1 Layout of the RF Section for t...

Страница 7: ...ation between traces pads to the adjacent GND pour in the areas of the matching networks This techni que will minimize the parasitic capacitance and reduce the detuning effects If space allows the nearby inductors of the matching network should be kept perpendicular to each other to reduce coupling be tween stages This helps to improve filter attenuation at higher harmonic frequencies The series m...

Страница 8: ...crystal and VDD traces to avoid any detuning effects on the crystal caused by the nearby power supply and to avoid the leakage of the crystal clk signal and its harmonics to the supply lines Figure 2 3 EFR32 Series 1 Layout Design Rules Dual band Reference Layout Top and Inner Layer 1 Use as many parallel grounding vias at the GND metal edges as possible especially at the edge of the PCB and along...

Страница 9: ...nes on inner layers for boards with more than two layers Avoid placing the supply lines close to the PCB edge To reduce sensitivity to PCB thickness variations use 50 Ω grounded coplanar lines where possible for connecting the antenna or the U FL connector to the matching network This also reduces radiation and coupling effects A general rule is to use 50 Ω trans mission lines where the length of ...

Страница 10: ...T 0 018 0 035 mm εr 4 6 H 0 325 mm G 0 25 mm W 0 45 mm Notes 1 Characteristic impedance is not super sensitive to the gap value It should be between 0 25 and 0 4 mm to have 47 through 53 Ω impedance 2 Different impedance calculators may yield slightly different results 3 H is the distance between the top and the first inner layer Figure 2 7 Grounded Coplanar Line Parameters AN928 1 EFR32 Series 1 ...

Страница 11: ...t uses a 915 MHz matching similar design practices should be applied with matching networks for other sub GHz frequencies as well The layout structure for the RF part of the EFR32 Series 1 Dual band Reference Radio Board is shown in the figure below the sub GHz matching is highlighted by a blue frame Figure 2 8 Layout of the RF Section for the EFR32 Series 1 Dual band Reference Radio Board sub GHz...

Страница 12: ...e chip As a result the first TX matching network components can be connected only with relatively long traces No traces should be routed on the layer beneath the traces that connects the first TX matching components with TX pins It is recommended to add an isolating ground metal with many vias between the 2 4 GHz and sub GHz matching networks The following figures illustrate layer consistency arou...

Страница 13: ...tching Area on the EFR32 Series 1 Dual band Reference Layout Bottom layer AN928 1 EFR32 Series 1 Layout Design Guide Guidelines for Layout Design When Using EFR32 Wireless MCUs silabs com Building a more connected world Rev 0 5 13 ...

Страница 14: ...und metal exist between the crystal and the RFVDD feed 7 Are the smallest value VDD filtering ca pacitors kept as close as possible to the VDD pins RFVDD PAVDD VREGVDD AVDD DVDD IOVDD of the EFR32 8 Are there multiple thermal straps used with the shunt capacitors 9 Do the ground pins of the shunt capaci tors use multiple vias 10 Does the exposed pad footprint use mul tiple vias 11 Is there at leas...

Страница 15: ...ND metal edges closed by stitching vias where possible with a via distance less than lambda 10 of the highest usually 10th critical harmonic frequency 17 Are 50 Ω grounded coplanar lines used for RF traces longer than λ 16 at the fun damental frequency 18 Are there vias at the ground metalliza tion near the 50 Ω transmission lines 19 Are the RF related parts especially the antenna placed far away ...

Страница 16: ...harmonic filtering capaci tors connected to ground planes on dif ferent sides of the transmission line 22 Is the area on the first inner layer be neath the RF chip and the matching net work filled with continuous GND metal and was wiring and routing avoided in this region AN928 1 EFR32 Series 1 Layout Design Guide Checklists silabs com Building a more connected world Rev 0 5 16 ...

Страница 17: ...ied on all inner layers beneath the area of the RX matching network 26 Is the area on the first inner layer be neath the balun and low pass filter filled with continuous GND metal and was wiring and routing avoided in this re gion 27 Is wiring and routing avoided on the lay er beneath the traces that connect the first TX matching network components with TX pins AN928 1 EFR32 Series 1 Layout Design...

Страница 18: ...ts The products are not designed or authorized to be used within any FDA Class III devices applications for which FDA premarket approval is required or Life Support Systems without the specific written consent of Silicon Labs A Life Support System is any product or system intended to support or sustain life and or health which if it fails can be reasonably expected to result in significant persona...

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