Renesas RX23W Series Installation and operating instructions

Application Note

R01AN4534EJ0201 Rev.2.01 Page 1 of 52

Sep.30.21

RX23W Group

Guidelines for Bluetooth Board Design

Introduction

This document describes RF board design guidelines for RX23W Bluetooth®5.0 (Core Specification v5.0)

RF transceiver. Please refer "RX Family Hardware Design Guide for board design" (R01AN1411) except

Bluetooth 5.0 RF transceiver part.

Target Device

RX23W Group

Note: The contents of this document are provided as a reference and do not guarantee the signal quality in

the system. When designing the actual system, thoroughly evaluate the product in the overall system

and apply these contents on your own responsibility.

Contents

1. Overview.................................................................................................................................... 3

1.1 Related documents ................................................................................................................................. 3

2. Board design guidelines for RX23W QFN ................................................................................. 4

2.1 RX23W QFN Pin list................................................................................................................................ 4

2.2 Oscillator circuit for Bluetooth-dedicated clock ....................................................................................... 5

2.3 Antenna connection pin........................................................................................................................... 8

2.4 Power supply mode for Bluetooth 5.0 RF transceiver........................................................................... 12

2.4.1 DC-DC converter mode....................................................................................................................... 12

2.4.2 Linear regulator mode ......................................................................................................................... 15

2.5 Power supply and ground patterns........................................................................................................ 17

2.5.1 Power supply....................................................................................................................................... 17

2.5.2 Ground................................................................................................................................................. 18

2.6 Circuit diagram for reference................................................................................................................. 20

2.7 Parts list for reference ........................................................................................................................... 21

3. Board design guidelines for RX23W BGA ............................................................................... 22

3.1 RX23W BGA Pin list.............................................................................................................................. 22

3.2 Oscillator circuit for Bluetooth-dedicated clock ..................................................................................... 23

3.3 Antenna connection pin......................................................................................................................... 26

3.4 Power supply mode for Bluetooth 5.0 RF transceiver........................................................................... 30

3.4.1 DC-DC converter mode....................................................................................................................... 30

3.4.2 Linear regulator mode ......................................................................................................................... 33

3.5 Power supply and ground patterns........................................................................................................ 35

3.5.1 Power supply....................................................................................................................................... 35

RX23W Group Guidelines for Bluetooth Board Design

R01AN4534EJ0201 Rev.2.01 Page 2 of 52

Sep.30.21

3.5.2 Ground................................................................................................................................................. 36

3.6 Circuit diagram for reference................................................................................................................. 38

3.7 Parts list for reference ........................................................................................................................... 39

4. Board design guidelines for RX23W LGA ............................................................................... 40

4.1 RX23W LGA Pin list .............................................................................................................................. 41

4.2 Oscillator circuit for Bluetooth-dedicated clock ..................................................................................... 43

4.3 Antenna connection pin......................................................................................................................... 43

4.4 Power supply mode for Bluetooth 5.0 RF transceiver........................................................................... 44

4.5 Ground................................................................................................................................................... 44

4.6 Antenna layout....................................................................................................................................... 46

4.7 Main Board Design................................................................................................................................ 48

4.8 Emission characteristics........................................................................................................................ 49

4.9 Housing Design ..................................................................................................................................... 50

4.10 Foot pattern design example................................................................................................................. 51

Revision History .............................................................................................................................. 52

The Bluetooth®word mark and logos are registered trademarks owned by Bluetooth SIG, Inc. and any use of

such marks by Renesas Electronics Corporation is under license. Other trademarks and registered

trademarks are the property of their respective owners.

RX23W Group Guidelines for Bluetooth Board Design

R01AN4534EJ0201 Rev.2.01 Page 3 of 52

Sep.30.21

1. Overview

Sections 2, 3, and 4 of this document describe board design guidelines for RX23W QFN package, RX23W

BGA package, and RX23W LGA package, respectively. This document briefly describes the Bluetooth 5.0

RF transceiver unit pins used in the RX23W.

1.1 Related documents

The following documents are related to this application note. Also refer to these documents when using this

application note.

•RX23W group User’s Manual: Hardware (R01UH0823)

•RX Family Hardware Design Guide (R01AN1411)

•RX23W group Tuning procedure of Bluetooth dedicated clock frequency (R01AN4762)

RX23W Group Guidelines for Bluetooth Board Design

R01AN4534EJ0201 Rev.2.01 Page 4 of 52

Sep.30.21

2. Board design guidelines for RX23W QFN

2.1 RX23W QFN Pin list

Table 2-1 is the description of Bluetooth 5.0 RF transceiver unit pins in RX23W QFN.

Table 2-1 Description of Bluetooth 5.0 RF transceiver unit pins in RX23W QFN

Pin Number

Pin Name

I/O

Functions

48 CLKOUT_RF Output

Bluetooth-Dedicated clock output pin, whose frequency can be set to 4,

2, or 1MHz. The default output setting is off. Connecting the clock

output pin to the external clock input pin of MCU, the RF clock can be

used as the MCU system clock.

32 ANT In/Out

RF single I/O pin for RF transceiver.

Adjust the characteristic impedance of the signal line to 50ohm.

38 XTAL1_RF Input

Pins for connecting the Bluetooth-dedicated clock oscillator. 32-MHz

oscillator connection pin

37 XTAL2_RF Output

Pins for connecting the Bluetooth-dedicated clock oscillator. 32-MHz

oscillator connection pin

40 DCLOUT

Output

RF transceiver power-supply (DC-DC converter or linear regulator) output pin

46 DCLIN_A Input

RF transceiver power-supply output connection pin. This pin should be

connected to an external inductor and capacitor when the DC-DC

converter mode is selected. When the linear regulator mode is selected,

this pin should be connected to an external capacitor.

45 DCLIN_D Input

RF transceiver power-supply output connection pin. This pin should be

connected to an external inductor and capacitor when the DC-DC

converter mode is selected. When the linear regulator mode is selected,

this pin should be connected to an external capacitor.

44 VCC_RF

Input

RF transceiver power supply pin

39 AVCC_RF

Input

RF transceiver power supply pin

28 ICGND

(VSS_RF)

Input

RF transceiver ground pin.

In this document, this pin is called “ICGND”.

Exposed Die

Pad VSS_RF Input RF transceiver ground pin

RX23W Group Guidelines for Bluetooth Board Design

R01AN4534EJ0201 Rev.2.01 Page 5 of 52

Sep.30.21

2.2 Oscillator circuit for Bluetooth-dedicated clock

Note the following when designing an oscillator circuit for Bluetooth-dedicated clock.

•Place the crystal resonator close to the “XTAL1_RF” and “XTAL2_RF” pins. We recommend the wiring

length between the RX23W and the crystal resonator of approximately 6 mm, as shown in "Figure 2-2

Example of the pattern around the crystal resonator".

•Shield the pattern for the “XTAL1_RF” and “XTAL2_RF” pins with the ground pattern. Do not place the

pattern for these signals in parallel with or across other patterns where a large current flows or the level

changes frequently.

•Not place any signal, power, and ground lines except the oscillator circuit’s on and below the oscillator

circuit area. We recommend that the ground pattern is placed in the layers under the oscillator circuit, as

shown in "Figure 2-2 Example of the pattern around the crystal resonator".

•Separate the oscillator circuit and the signal line from an antenna to “ANT” pin by placing slit patterns on

all layers.

•Ensure a return path in layer2 (additional layer3 if possible) from ground of the crystal resonator to

"Exposed Die Pad (VSS_RF)”, as shown in "Figure 2-2 Example of the pattern around the crystal

resonator".

•External load capacitors (CL) for frequency tuning are unnecessary, because the capacitors are built in

IC. For Tuning procedure of Bluetooth dedicated clock frequency, see the descriptions of the application

note, the Hardware Design Guide(R01AN4762). The latest version can be downloaded from the Renesas

Electronics website.

•Insert a damping resistor (Rd) as required. Set the resistance to the value recommended by the oscillator

manufacturer as the value depends on the oscillator and its driving capability. If the oscillator

manufacturer states that the addition of a feedback resistor (Rf) to the oscillator is required, insert Rf

between XTAL1_RF and XTAL2_RF according to the instructions.

•When the frequency-divided clock for the Bluetooth-dedicated clock is output, note designing board

pattern. The wiring length should be as short as possible. In addition, must not branch the wiring. And

avoid using vias on the transmission line. A maximum of 2 is recommended.

•Shield the transmission line of CLKOUT_RF with the "VSS" pattern to avoid noise couplings to

“VSS_RF”.

Note: Bluetooth 5.0 RF transceiver clock frequency accuracy which includes initial error, temperature drift,

and ageing effect should be less than or equal to +/-50ppm in the Bluetooth specification. Therefore,

the frequency error should be as less as possible.

Figure 2-1 shows an example of the crystal resonator connection. Figure 2-2 shows an example of the

pattern around the crystal resonator.

RX23W Group Guidelines for Bluetooth Board Design

R01AN4534EJ0201 Rev.2.01 Page 6 of 52

Sep.30.21

Note: The resistance of Rd and Rf should be determined thorough oscillation characteristics evaluation with

a crystal resonator to be mounted. These resistors might not be required, depending on the oscillation

characteristics.

Figure 2-1 Example of the crystal resonator connection.

Figure 2-2 Example of the pattern around the crystal resonator

XTAL2_RF

XTAL1_RF

VSS_RF

RX23W Group Guidelines for Bluetooth Board Design

R01AN4534EJ0201 Rev.2.01 Page 7 of 52

Sep.30.21

Table 2-2 shows confirmed operation crystal resonator list (reference).

Table 2-2 Tested crystal resonator list (reference)

Manufacturer Parts number

SMD/Lead

size code

(in mm)

Frequency

(MHz)

Frequency

Tolerance

(ppm)

Frequency

Stability

(ppm)

Equivalent

Series

Resistance

(ohm)

Load

Capacitance

(pF)

NDK NX1612SA-32.000MHZ-

CHP-CIS-3 1612 32.00 +/-10 +/-20 Max 100 6

NDK NX1210AB- 32.000MHZ-

CHP-CIX-3 1210 32.00 Total +/-30 Max 100 6

Kyocera CX1612DB32000

A0WPNC1 1612 32.00 Total +/-25 Max 100 5

Kyocera CX1210SB32000

B0GPJC1 1210 32.00 Total +/-30 Max 80 6

Murata XRCMD32M000FZQ52R0 1612 32.00 Total +/-30 Max 60 6

Murata XRCTD32M000N1P00R0 1210 32.00 Total +/-30 Max 120 6

RX23W Group Guidelines for Bluetooth Board Design

R01AN4534EJ0201 Rev.2.01 Page 8 of 52

Sep.30.21

2.3 Antenna connection pin

Note the followings for antenna connection pin design.

•Adjust the characteristic impedance of 50ohm for the signal line from an antenna to “ANT” pin. Optimize

the width of signal line and the gap between signal line and ground pattern, considering the PCB

permittivity and layer thickness. Depending on the antenna used, additional parts such as inductors or

capacitors may be required. In "Figure 2-3 Example of the pattern around “ANT” pin", the coplanar

waveguide is used.

•When mounting a connector, keep the characteristic impedance of 50ohm including the connector.

•The directly under layer of the coplanar waveguide should be solid ground, having no crossing with any

signal, power, and other ground lines.

•Place vias as many as possible between the coplanar waveguide ground pattern and the solid ground.

We recommend that the via spacing should be approximately 0.9mm, as shown in "Figure 2-3 Example

of the pattern around “ANT” pin".

Figure 2-3 shows an example of the pattern around “ANT” pin.

Figure 2-3 Example of the pattern around “ANT” pin

RX23W Group Guidelines for Bluetooth Board Design

R01AN4534EJ0201 Rev.2.01 Page 9 of 52

Sep.30.21

•Pay attention to an emission level of 5th order harmonics, when selecting 4 dBm transmitted output mode

and evaluating of US(FCC) regulatory with a coaxial cable. The emission should be suppressed with an

RF filter implementation.

RF filter requirements

Frequency band to be suppressed: 12.01 to 12.4 GHz

Minimum attenuation: 8dB

•Pay attention to an emission level of 3rd order harmonics, when selecting 0 dBm transmitted output mode

and evaluating of US(FCC) regulatory with a coaxial cable. The emission should be suppressed with an

RF filter implementation.

RF filter requirements

Frequency band to be suppressed: 7250 to 7440 MHz

Minimum attenuation: 2dB

This document describes an example of an open circuit stub and an example of LPF using SMD parts. Both

of these circuits can suppress 5th order harmonics of 4 dBm transmitted output mode and the 3rd order

harmonics of 0 dBm transmitted output mode.

Figure 2-4 shows an example of the open circuit stub.

Figure 2-4 Example of the open circuit stub

Note: The pattern width and pattern pitch for impedance control vary depending on board thickness,

material, and layer configuration. Contact the board manufacturer for more information.

Obtain an effective permittivity ɛ

r,eff

from the above board

composition.

effective permittivity ɛr,eff ≒3.515

The wavelength of 12400MHz is approximately 24.18 mm.

Then calculate the length of a stub by using the formula

below.

the length of a stub L= 0.25*λ / (ɛr,eff)0.5 = 3.224mm

Permittivity(ɛ

)=4.45

S=0.41mm

W=0.72mm

h=0.2mm

Frequency=12400MHz (2480MHz x 5)

Note: Place the open circuit stub as close to “ANT” pin as

possible. We recommend that it should place

approximately 3.5mm, as shown in example pattern

on the right figure.

RX23W Group Guidelines for Bluetooth Board Design

R01AN4534EJ0201 Rev.2.01 Page 10 of 52

Sep.30.21

Figure 2-5 shows an example of LPF using SMD parts

Figure 2-5 Example of LPF using SMD parts

Note: Depending on the PCB design, the value may differ. Adjust the value, if necessary.

ANT

L201

C201

C201 = GJM1555C1HR20WB01 (0.2pF +/-0.05pF)

L201 = LQG15HS1N5S02 (1.5nH +/-0.3nH)

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