SI4826_技术文档

AN602

Si4822/26/27/40/44 ANTENNA, SCHEMATIC, LAYOUT,

AND DESIGN GUIDELINES

1. Introduction

This document provides general Si4822/26/27/40/44 design and AM/FM/SW antenna selection guidelines,

including schematic, BOM, and PCB layout. All users should follow the Si4822/26/27/40/44 design guidelines

presented in “2. Si4822/26/27/40/44 Default Frequency Band Definition and Selection”and “3. Si48422/26/27/40/44

SSOP/SOIC Schematic and Layout” and choose the appropriate antennas based on the applications and device

used as described in “4. Headphone Antenna for FM Receive” through “8. Whip Antenna for SW Receiver”.

Table 1. Part Selection Guide

†Part

†General

Number

Description

†

†

†

Si4822

Si4826

Si4827

Entry level wheel-tuned digital display

AM/FM Receiver, Mono audio

†

Entry level wheel-tuned digital display

AM/FM/SW Receiver, Mono audio

Entry level wheel-tuned digital display

AM/FM/SW Receiver, wide FM/SW

band, Mono audio

†

Si4840

Si4844

Wheel-tuned digital display AM/FM

Receiver, Stereo audio

†

Wheel-tuned digital display AM/FM/

SW Receiver, wide FM/SW band, Ste-

reo audio

Rev. 0.3 2/13

AN602

2. Si4822/26/27/40/44 Default Frequency Band Definition and Selection

For Si4822/26/27/40/44, there are two methods for defining a frequency band, one is to select one of the chip

internal default bands by using the slide switch and resistor ladder. Another method is to use the host MCU

sending command to make the chip work in the desired band. Refer to application note, “AN610: Si48xx ATDD

Programming Guide”, for information on how to use the Si4822/26/27/40/44 to define a frequency band and set a

band property. This section describes how to select the default frequency band by using the slide switch and

resistors ladder.

The Si4822/40 has five defined FM bands and five defined AM bands. The Si4826/27/44 has an added 16 SW

bands. In each FM band, the parts also offer two de-emphasis selections and two LED stereo separation threshold

selections, which results in a total 41 combinations to choose from.

The Si4822/26/40/44-A supports FM band range less than 23 MHz and SW band range less than 1.15 MHz. The

Si4827-A/44-B supports wider FM/SW band range. Refer to application note, “AN610: Si48xx ATDD Programming

Guide” for details.

2.1. Si4822/26/27/40/44 Default Band Definition

For Si4822/26/27/40/44, the FM band definition is in fact a combination of frequency range, de-emphasis, and LED

stereo separation threshold. Customers should choose the band according to not only frequency range, but also

de-emphasis setting and LED stereo separation requirements. For AM and SW, simply choose the band according

to the frequency range desired.

Table 2. Band Sequence Definition

Band

Number

Band

Name

Band Frequency

Range

De-emphasis (FM)

Stereo LED on

Conditions

Total R to GND

(k, 1%)

Channel Space (AM)

(Only for Si4840/44)

Band1

Band2

Band3

Band4

Band5

Band6

Band7

Band8

Band9

FM1

FM2

FM3

87–108 MHz

75 µs

50 µs

75 µs

50 µs

75 µs

Separation = 6 dB,

RSSI = 20

ꢀ47

ꢀ57

ꢀ67

ꢀ77

ꢀ87

ꢀ97

ꢀ107

ꢀ117

ꢀ127

Separation = 12 dB,

RSSI = 28

87–108 MHz

Separation = 6dB,

RSSI = 20

87–108 MHz

Separation = 12 dB,

RSSI = 28

86.5–109 MHz

87.3–108.25 MHz

Separation = 6 dB,

RSSI = 20

Separation = 12 dB,

RSSI = 28

Separation = 6 dB,

RSSI = 20

Separation = 12 dB,

RSSI = 28

Separation = 6 dB,

RSSI = 20

2

Rev. 0.3

AN602

Table 2. Band Sequence Definition (Continued)

Band

Number

Band

Name

Band Frequency

Range

De-emphasis (FM)

Stereo LED on

Conditions

Total R to GND

(k, 1%)

Channel Space (AM)

(Only for Si4840/44)

Band10

Band11

Band12

Band13

Band14

Band15

Band16

Band17

Band18

Band19

Band20

FM3

FM4

FM5

87.3–108.25 MHz

76–90 MHz

50 µs

75 µs

50 µs

75 µs

50 µs

75 µs

50 µs

Separation = 12 dB,

RSSI = 28

ꢀ137

ꢀ147

ꢀ157

ꢀ167

ꢀ177

ꢀ187

ꢀ197

ꢀ207

ꢀ217

ꢀ227

ꢀ237

Separation = 6 dB,

RSSI = 20

Separation = 12 dB,

RSSI = 28

Separation = 6 dB,

RSSI = 20

76–90 MHz

Separation = 12 dB,

RSSI = 28

76–90 MHz

Separation = 6 dB,

RSSI = 20

76–90 MHz

Separation = 12 dB,

RSSI = 28

64–87 MHz

Separation = 6 dB,

RSSI = 20

64–87 MHz

Separation = 12 dB,

RSSI = 28

64–87 MHz

Separation = 6 dB,

RSSI = 20

64–87 MHz

Separation = 12 dB,

RSSI = 28

Band21

Band22

Band23

Band24

Band25

Band26

Band27

Band28

Band29

Band30

AM1

AM2

AM3

AM4

AM5

SW1

SW2

SW3

SW4

SW5

520–1710 kHz

522–1620 kHz

504–1665 kHz

520–1730 kHz

510–1750 kHz

5.6–6.4 MHz

5.95–6.2 MHz

6.8–7.6 MHz

7.1–7.6 MHz

9.2–10 MHz

ꢀ10 kHz

ꢀ9 kHz

ꢀ10 kHz

ꢀ247

ꢀ257

ꢀ267

ꢀ277

ꢀ287

ꢀ297

ꢀ307

ꢀ317

ꢀ327

ꢀ337

Rev. 0.3

3

AN602

Table 2. Band Sequence Definition (Continued)

Band

Number

Band

Name

Band Frequency

Range

De-emphasis (FM)

Stereo LED on

Conditions

Total R to GND

(k, 1%)

Channel Space (AM)

(Only for Si4840/44)

Band31

Band32

Band33

Band34

Band35

Band36

Band37

Band38

Band39

Band40

Band41

SW6

SW7

9.2–9.9 MHz

11.45–12.25 MHz

11.6–12.2 MHz

13.4–14.2 MHz

13.57–13.87 MHz

15–15.9 MHz

ꢀ347

ꢀ357

ꢀ367

ꢀ377

ꢀ387

ꢀ397

ꢀ407

ꢀ417

ꢀ427

ꢀ437

ꢀ447

SW8

SW9

SW10

SW11

SW12

SW13

SW14

SW15

SW16

15.1–15.8 MHz

17.1–18 MHz

17.48–17.9 MHz

21.2–22 MHz

21.45–21.85 MHz

2.2. Default Band Selection

Refer to Figure 1 for the band selection circuits. Selecting a band is to determine the resistance value from the

band select pin to GND.

To select a specific band, you need to ensure two things:

Total value of resistance from the BAND to GND is equal to the value specified in Table 2

Total resistance from TUNE1 to GND is 500 k in 1% tolerance

Some commonly used bands and their respective selection circuits are listed below for your quick reference.

2.2.1. Typical 12-band application

Figure 1 and Table 3 illustrate the band and resistor value details for a typical 12-band application.

4

Rev. 0.3

AN602

TUNE1

R36

33k 1%

R43

30k 1%

SW15 (21.2MHz - 22MHz)

SW13 (17.1MHz - 18MHz)

R35

20k 1%

R15

20k 1%

SW11 (15MHz - 15.9MHz)

SW9 (13.4MHz - 14.2MHz)

R10

20k 1%

Si4826/27/44 only

R12

20k 1%

S2

SW7(11.45MHz - 12.25MHz)

1

2

BAND

R11

20k 1%

3

4

5

6

7

SW5(9.2MHz - 10.0MHz)

SW3(6.8MHz - 7.6MHz)

8

9

R14

20k 1%

10

11

12

13

R9

20k 1%

SW1 (5.6MHz - 6.4MHz)

AM1 (520kHz - 1710kHz)

R8

50k 1%

R7

40k 1%

FM5 (64MHz - 87MHz)

R28

40k 1%

FM4 (76MHz - 90MHz)

FM1 (87MHz - 108MHz)

R29

120k 1%

R33

0R 1%

R44

47k 1%

Figure 1. A Typical 12-Band Selection Circuit

Rev. 0.3

5

AN602

Table 3. Typical 12-Band Selection

Band

Number

Band

Name

Band Frequency

De-emphasis (FM)

Stereo LED On

Conditions (Only

for Si4840/44)

Total R to GND

Range

(k, 1%)

Channel space (AM)

Band1

Band13

Band17

FM1

FM4

FM5

87–108 MHz

76–90 MHz

64–87 MHz

75 µs

Separation = 6 dB,

RSSI = 20

ꢀ47

ꢀ167

ꢀ207

Separation = 6 dB,

RSSI = 20

75 µs

Separation = 6 dB,

RSSI = 20

Band21

Band26

Band28

Band30

Band32

Band34

Band36

Band38

Band40

AM1

SW1

SW3

SW5

SW7

SW9

SW11

SW13

SW15

520–1710 kHz

5.6–6.4 MHz

ꢀ10 kHz

ꢀ247

ꢀ297

ꢀ317

ꢀ337

ꢀ357

ꢀ377

ꢀ397

ꢀ417

ꢀ437

6.8–7.6 MHz

9.2–10 MHz

11.45–12.25 MHz

13.4–14.2 MHz

15–15.9 MHz

17.1–18 MHz

21.2–22 MHz

2.2.2. Typical 2-band application for Europe

Figure 2 and Table 4 show the band and resistor value details for a typical European 2-band application.

Table 4. Typical European 2-Band Selection

Band

Number

Band

Name

Band Frequency

Range

De-emphasis (FM)

Stereo LED On

Conditions (Only

for Si4840/44)

Total R to GND

(k, 1%)

Channel space (AM)

Band4

FM1

AM2

87–108 MHz

50 µs

Separation = 12 dB,

RSSI = 28

ꢀ77

Band22

522–1620 kHz

ꢀ9 kHz

ꢀ257

6

Rev. 0.3

AN602

TUNE1

R3

243k 1%

S2

1

BAND

AM

FM

2

3

R4

180k 1%

R5

77k 1%

Figure 2. Typical 2-Band Selection Circuit for Europe

2.2.3. Typical 2-band Application for US

Figure 3 and Table 5 show the band and resistor value details for a typical 2-band application for US.

Table 5. Typical US 2-Band Selection

Band

Number

Band

Name

Band Frequency

Range

De-emphasis (FM)

Stereo LED On

Conditions (Only for

Si4840/44)

Total R to GND

(k, 1%)

Channel space (AM)

Band2

FM1

AM1

87–108 MHz

75 µs

Separation = 12 dB,

RSSI = 28

ꢀ57

Band21

520–1710 kHz

ꢀ10 kHz

ꢀ247

TUNE1

R3

253k 1%

S2

BAND

AM

FM

1

2

3

R4

190k 1%

R5

57k 1%

Figure 3. Typical 2-Band Selection Circuit for US

Rev. 0.3

7

AN602

3. Si48422/26/27/40/44 SSOP/SOIC Schematic and Layout

This section shows the typical schematic and layout required for optimal Si4822/26/27/40/44 performance. Si4822/

26/40/44 offer two methods to select the radio band by tuner setting and two methods to set band property by tuner

setting. Normally, there are four kinds of typical application circuits in real application, however, the Si4827 offers

two methods to select the radio band by tuner setting and two methods to set band property by host MCU, so there

are two kinds of typical application circuits in real application.

3.1. Si4822/26/40/44 Application Circuit: Host MCU Select Radio Band and Set Band

Property

Figure 4 shows the applications circuits of Si4822/26/40/44 when the application is to use the host MCU to select

radio band and set band property. Normally, a push button for selecting band is connected to the host MCU. The

MCU then detects the push button’s action and sends a command to Si4822/26/40/44 to set the desired band. The

host MCU can also set the band property, such as band top frequency point and bottom frequency point, stereo

indication threshold (only for Si4840/44), de-emphasis, AM tuning spacing, etc. The two key points to ensure

Si4822/26/40/44 works properly are as follows:

1. No pull-up resistor is connected to pin 1 LNA_EN

2. Pin 5 BAND is connected to its power supply V directly

CC

C6 & C15 are required bypass capacitors for V

/V

power supply pin 20/21. Place C6/C15 as close as

DD1 DD2

possible to the V

/V

pin 20/21 and DBYP pin 22. These recommendations are made to reduce the size of the

DD1 DD2

current loop created by the bypass cap and routing, minimize bypass cap impedance, and return all currents to the

DBYP pin.

Pin 22 is the dedicated bypass capacitor pin. Do not connect it to power supply GND on PCB.

Pin 13 and pin 14 are the GND of the chip; these pins must be well connected to the power supply GND on PCB.

Pin 9 is the RFGND of the chip; it must be well connected to the power supply GND on PCB.

C4 and/or C7 (4.7 µF) are ac coupling caps for receiver analog audio output from pin 23 and/or pin 24. The input

resistance of the amplifier, R, such as a headphone amplifier, and the capacitance, C, will set the high pass pole

given by Equation 1. Placement locations of C4 and C7 are not critical.

1

f_c= ---------------

2RC

Equation 1. High-Pass Pole Calculation

C28 and C29 (22 pF) are crystal loading caps required only when using the internal oscillator feature. Refer to the

crystal data sheet for the proper load capacitance and be certain to account for parasitic capacitance. Place caps

C28 and C29 such that they share a common GND connection and the current loop area of the crystal and loading

caps is minimized.

Y1 (32.768 kHz) is an optional crystal required only when using the internal oscillator feature. Place the crystal Y1

as close to XTALO pin 18 and XTALI pin 19 as possible to minimize current loops. If applying an external clock

(32.768 kHz) to XTALI, leave XTALO floating.

Do not route digital signals or reference clock traces near pin 6 and 7. Do not route Pin 6 & 7. These pins must be

left floating to guarantee proper operation.

Pin 2, 15, 16, 17 are the required communication pins with host MCU. A 100 k pull-up resistor R6 and 0.1 µF

bypass cap C19 are recommended for the pin 15 RST. Pull-up resistor R3 of 10 k is necessary for pin 16 SDIO.

VR1 (100 k / 10%), R27, C1, C13 constitute the tuning circuit. 100kat 10% tolerance is recommended for VR1.

Q1(2SC9018), together with its peripherals B6, C30,31,33,36, R31,32,34,41, is the LNA circuit for all SW bands.

The LNA is switched off by LNA_EN signal in AM and FM mode controlled by Si4826/44.

For Si4822/26, do not route pin 23. This pin must be left floating to guarantee proper operation.

8

Rev. 0.3

AN602

ANT2

TUNE1

FM/SW

VR1

100k 10%

C13 C1

47u 0.1u

VCC

R27

100R

C36

0.47u

R32

10R

C34

33p

C31

33n

L2

To host MCU

IRQ

VCC

270nH

R31

1k

C33

LNA_EN

[1]

C5

[1] LNA_EN

R41

120k

10p

0.47u

C30

B6

2.5k/100M

33n

Q1

2SC9018

R34

100k

Si4822/26/40/44

C4

LOUT

(For Si4822/26, pin24 is AOUT)

^ROUT(For Si4822/26, pin23 is NC)

4.7u

C7

4.7u

C19

0.1u

Si4826/44 only

R6

100k

C6 C15

RESET

0.1u 4.7u

R3

10k

To host MCU

SDIO

SCLK

Y1

32.768KHz

C28

22p

C29

22p

Optional

Figure 4. Si4822/26/40/44 Applications Circuit: MCU Select Band and Set Band Property

Rev. 0.3

9

AN602

3.2. Si4822/26/40/44 Application Circuits: Host MCU Select Default Band and Use Default

Band Property

Figure 5 shows Si4822/26/40/44 application circuits that enable the host MCU to select default bands. In this

application, the host MCU sends commands to Si4822/26/40/44 to select the desired default band. However, the

MCU cannot define those band properties already fixed in the default band definition, as stated in “2.1. Si4822/26/

27/40/44 Default Band Definition”. The host MCU can only define the band properties which are not fixed in the

default band definition, such as softmute property, etc. For more details, refer to “AN610: Si48xx ATDD

Programming Guide”. The two key points to ensure Si4822/26/40/44 works properly are as follows:

1. Add pull-up resistor R42 of 10k to pin 1 LNA_EN.

2. Ensure pin 5 BAND is connected to its power supply V directly.

CC

ANT2

TUNE1

FM/SW

VR1

100k 10%

C13 C1

47u 0.1u

VCC

R27

100R

C36

0.47u

R32

10R

C34

33p

IRQ

To host MCU

C31

33n

L2

R42

10k

VCC

270nH

R31

1k

C33

LNA_EN

[1]

C5

[1] LNA_EN

R41

120k

10p

0.47u

C30

B6

2.5k/100M

33n

Q1

2SC9018

R34

100k

Si4822/26/40/44

C4

LOUT

(For Si4822/26, pin24 is AOUT)

ROUT (For Si4822/26, pin23 is NC)

4.7u

C7

4.7u

C19

0.1u

Si4826/44 only

R6

100k

C6 C15

RESET

0.1u 4.7u

R3

To host MCU

10k

SDIO

SCLK

Y1

32.768KHz

C28

22p

C29

22p

Optional

Figure 5. SiSi4822/26/40/44 Applications Circuit: MCU Select Default Band and Use Default Band

Property

10

Rev. 0.3

AN602

3.3. Si4822/26/40/44 Application Circuits: Slide Switch Select Band and MCU Re-define

Band Property

Figure 7 illustrates an Si4822/26/40/44 application circuit which uses a slide switch for band selection and enables

the host MCU to re-define the band property. For the band selection method using slide switch and resistors ladder,

refer to "2.2. Default Band Selection" on page 4. In this application, the user can select any default band and the

MCU will re-define the band’s property according to the design requirement. The MCU can only re-define the

selected band’s property, it cannot change an FM band to an AM or SW band, and vice versa. The two key points

to ensure the Si4822/26/40/44 works properly are as follows:

1. No pull-up resistor is connected to pin 1 LNA_EN.

2. Pin 5 BAND is connected to slide switch.

[1]

TUNE1

R36

33k 1%

R43

30k 1%

ANT2

[1]

TUNE1

SW15 (21.2MHz - 22MHz)

SW13 (17.1MHz - 18MHz)

VR1

100k 10%

FM/SW

R35

20k 1%

C13 C1

47u 0.1u

VCC

R27

100R

C36

0.47u

R15

20k 1%

R32

10R

SW11 (15MHz - 15.9MHz)

SW9 (13.4MHz - 14.2MHz)

Si4826/44 only

C34

33p

R10

20k 1%

C31

33n

IRQ

To host MCU

L2

270nH

R31

1k

C33

LNA_EN

[1]

[1] LNA_EN

C5

R41

R12

20k 1%

120k

10p

0.47u

C30

B6

S2

SW7(11.45MHz - 12.25MHz)

2.5k/100M

1

2

BAND

33n

[1]

Q1

2SC9018

R11

20k 1%

3

4

R34

100k

5

6

Si4822/26/40/44

C4

7

SW5(9.2MHz - 10.0MHz)

SW3(6.8MHz - 7.6MHz)

8

9

R14

20k 1%

10

11

12

13

LOUT

4.7u

C7

(For Si4822/26, pin24 is AOUT)

(For Si4822/26, pin23 is NC)

ROUT

4.7u

R9

20k 1%

C19

0.1u

Si4826/44 only

R6

SW1 (5.6MHz - 6.4MHz)

AM1 (520kHz - 1710kHz)

100k

C6 C15

R8

RESET

50k 1%

0.1u 4.7u

R3

10k

To host MCU

SDIO

SCLK

R7

20k 1%

Y1

FM5 (64MHz - 87MHz)

32.768KHz

R28

40k 1%

C28

22p

C29

22p

FM4 (76MHz - 90MHz)

FM1 (87MHz - 108MHz)

R29

120k 1%

Optional

R33

20k 1%

R44

47k 1%

Figure 6. Si4822/26/40/44 Applications Circuit: Slide Switch Select Band and

MCU Re-define Band Property

Rev. 0.3

11

AN602

3.4. Si4822/26/40/44 Application Circuits: Slide Switch Select Band and

Use Default Band Property

Figure 7shows an application circuit that uses a slide switch for band selection. In this example, the host MCU

cannot change those band properties already fixed in the default band definition, as stated in section 2.1, it can

only define the band properties which are not fixed in the default band definition, such as softmute property, etc.

For more details, refer to “AN610: Si48xx ATDD Programming Guide”. The two key points to ensure Si4822/26/40/

44 works properly are as follows:

1. Add pull-up resistor R42 of 10 k to pin 1 LNA_EN.

2. Pin 5 BAND is connected to slide switch.

[1]

TUNE1

R36

33k 1%

R43

30k 1%

SW15 (21.2MHz - 22MHz)

SW13 (17.1MHz - 18MHz)

ANT2

[1]

TUNE1

R35

20k 1%

FM/SW

VR1

100k 10%

C13 C1

47u 0.1u

VCC

R15

20k 1%

R27

100R

C36

0.47u

SW11 (15MHz - 15.9MHz)

SW9 (13.4MHz - 14.2MHz)

R32

10R

R10

20k 1%

Si4826/44 only

IRQ

C34

33p

To host MCU

C31

33n

L2

270nH

R42

10k

R31

1k

C33

LNA_EN

[1]

R12

20k 1%

C5

[1] LNA_EN

R41

120k

S2

SW7(11.45MHz - 12.25MHz)

10p

0.47u

C30

B6

1

2

BAND

[1]

R11

20k 1%

3

2.5k/100M

4

33n

Q1

2SC9018

5

6

7

R34

100k

SW5(9.2MHz - 10.0MHz)

SW3(6.8MHz - 7.6MHz)

8

Si4822/26/40/44

9

R14

20k 1%

10

11

12

13

C4

LOUT

ROUT

(For Si4822/26, pin24 is AOUT)

(For Si4822/26, pin23 is NC)

4.7u

C7

R9

20k 1%

4.7u

C19

0.1u

Si4826/44 only

SW1 (5.6MHz - 6.4MHz)

AM1 (520kHz - 1710kHz)

R6

R8

100k

50k 1%

C6 C15

RESET

R3

10k

0.1u 4.7u

To host MCU

R7

SDIO

SCLK

20k 1%

FM5 (64MHz - 87MHz)

FM4(76MHz - 90MHz)

FM1 (87MHz - 108MHz)

Y1

R28

40k 1%

32.768KHz

C28

22p

C29

22p

R29

120k 1%

Optional

R33

20k 1%

R44

47k 1%

Figure 7. Si4822/26/40/44 Applications Circuit: Slide Switch Select Band and Use Default Band

Property

12

Rev. 0.3

AN602

3.5. Si4827 Application Circuit: Host MCU to Select Radio Band

Figure 8 shows the Si4827 application circuit that the host MCU uses to select radio band. In this application, the

host MCU sends commands to the Si4827 to select the desired band. Setting the band property by MCU or using

the tuner default band property is determined by host MCU.

Setting the band property by MCU means that the host MCU can set the band property, such as band top

frequency point and bottom frequency point, de-emphasis, AM tuning spacing, etc.

Using the tuner default band property means that the MCU cannot define those band properties already fixed in the

default band definition, as stated in section “2.1. Si4822/26/27/40/44 Default Band Definition”. The host MCU can

only define the band properties which are not fixed in the default band definition, such as softmute property, etc.

For more details, refer to application note, "AN610: Si48xx ATDD Programming Guide".

The key point to ensure the Si4827 works properly is that pin 4 BAND is connected to it's power supply V

directly.

CC

Figure 8. Si4827 Application Circuit: Host MCU Select Band

Rev. 0.3

13

AN602

3.6. Si4827 Application Circuit: Slide Switch Select Band

Figure 9 shows the Si4827 application circuit in which a slide switch is used for band selection. For the band

selection method using slide switch and resistors ladder, refer to section.“2.2. Default Band Selection”. Setting the

band property by MCU or using the tuner default band property is determined by host MCU.

When setting the band property by MCU, the user can select any default band and the MCU will re-define the

band's property according to the design requirement. The MCU can only re-define the selected band's property, it

cannot change an FM band to an AM or SW band, and vice versa.

When using the tuner default band property, the host MCU cannot change those band properties already fixed in

the default band definition, as stated in section “2.1. Si4822/26/27/40/44 Default Band Definition”, it can only define

the band properties which are not fixed in the default band definition, such as softmute property, etc. For more

details, refer to application note, "AN610: Si48xx ATDD Programming Guide".

The key point to ensure the Si4827 works properly is that pin 4 BAND is connected to slide switch.

Figure 9. Si4827 Application Circuit: Slide Switch Select Band

14

Rev. 0.3

AN602

3.7. Si4822/26/27/40/44 Bill of Materials

Table 6. Si4822/26/40/44 Applications Circuit: Host MCU Select Band and Set Band Property

Component(s)

Value/Description

Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R

Capacitor, 0.47 µF, ±20%, Z5U/X7R

RF coupling capacitors, 33 pF, ±5%, COG

Capacitor 4.7 µF, ±20%, Z5U/X7R

Capacitor 47 µF, ±20%, Z5U/X7R

Resistor, 100 , ±5%

Supplier

Murata

C1,C6,C19

C5

Murata

C34

Murata

C4,C7,C15

C13

Murata

R27

Venkel

R6

Resistor, 100 k, ±5%

Venkel

R3

Resistor, 10 k, ±5%

Venkel

U1

Si4822/26/40/44 AM/FM/SW Analog Tune Digital Display Radio

Tuner

Silicon Laboratories

L2

Inductor 270 nH

Murata

Jiaxin Electronics

Various

ANT1

ANT2

VR1

MW ferrite antenna 220 µH.

Whip antenna

Variable resistor (POT), 100 k, ±10%

Si4826/44 Only

Changtaier

C36

C33

C30-31

B6

Capacitor, 0.47 µF, ±20%, Z5U/X7R

Capacitor, 10 pF, ±5%, COG

Capacitor, 33 nF, ±5%, COG

Ferrite bead,2.5 k/100 MHz.

RF transistor, 2SC9018.

Resistor, 100 k, ±5%

Resistor, 120 k, ±5%

Resistor, 10 , ±5%

Murata

ETC

Q1

R34

R41

R32

R31

Venkel

Resistor, 1 k, ±5%

Optional

C28, C29

Y1

Crystal load capacitors, 22 pF, ±5%, COG (Optional: for crystal

oscillator option)

Murata

Epson

32.768 kHz crystal (Optional: for crystal oscillator option)

Rev. 0.3

15

AN602

Table 7. Si4822/26/40/44 Applications Circuit: MCU Select Default Band and Use Default Band

Property

Component(s)

C1,C6,C19

C5

Value/Description

Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R

Capacitor, 0.47 µF, ±20%, Z5U/X7R

RF coupling capacitors, 33 pF, ±5%, COG

Capacitor 4.7 µF, ±20%, Z5U/X7R

Capacitor 47 µF, ±20%, Z5U/X7R

Resistor, 100 , ±5%

Supplier

Murata

C34

Murata

C4,C7,C15

C13

Murata

R27

Venkel

R6

Resistor, 100 k, ±5%

Venkel

R3, R42

U1

Resistor, 10 k, ±5%

Venkel

Si4822/26/40/44 AM/FM/SW Analog Tune Digital Display Radio

Tuner

Silicon Laboratories

L2

Inductor 270 nH

Murata

Jiaxin Electronics

Various

ANT1

ANT2

VR1

MW ferrite antenna 220 µH.

Whip antenna

Variable resistor (POT), 100 k, ±10%

Si4826/44 Only

Changtaier

C36

C33

C30-31

B6

Capacitor, 0.47 µF, ±20%, Z5U/X7R

Capacitor, 10 pF, ±5%, COG

Capacitor, 33 nF, ±5%, COG

Ferrite bead, 2.5 k/100 MHz

RF transistor, 2SC9018.

Resistor, 100 k, ±5%

Resistor, 120 k, ±5%

Resistor, 10 , ±5%

Murata

ETC

Q1

R34

R41

R32

R31

Venkel

Resistor, 1 k, ±5%

Optional

C28, C29

Y1

Crystal load capacitors, 22 pF, ±5%, COG

for crystal oscillator option)

(Optional:

Murata

Epson

32.768 kHz crystal (Optional: for crystal oscillator option)

16

Rev. 0.3

AN602

Table 8. Si4822/26/40/44 Application Circuits: Slide Switch Select Band and MCU Re-define Band

Property

Component(s)

C1,C6,C19

C5

Value/Description

Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R

Capacitor, 0.47 µF, ±20%, Z5U/X7R

RF coupling capacitors, 33 pF, ±5%, COG

Capacitor 4.7 µF, ±20%, Z5U/X7R

Capacitor 47 µF, ±20%, Z5U/X7R

Resistor, 100 , ±5%

Supplier

Murata

C34

Murata

C4,C7,C15

C13

Murata

R27

Venkel

R6

Resistor, 100 k, ±5%

Venkel

R3

Resistor, 10 k, ±5%

Venkel

R7,R33

R28

Band switching resistor, 20 k, ±1%

Band switching resistor, 40 k, ±1%

Band switching resistor, 120 k, ±1%

Band switching resistor, 47 k, ±1%

Band switching resistor, 30 k, ±1%

Band switching resistor, 33 k, ±1%

Venkel

R29

Venkel

R44

Venkel

R43

Venkel

R36

Venkel

U1

Si4822/26/40/44 AM/FM/SW Analog Tune Digital Display Radio

Tuner

Silicon Laboratories

L2

Inductor 270 nH

MW ferrite antenna 220 µH

Whip antenna

Murata

Jiaxin Electronics

Various

ANT1

ANT2

VR1

S2

Variable resistor (POT), 100 k, ±10%

Slide switch

Changtaier

Shengda

Si4826/44 Only

C36

C33

C30-31

B6

Murata

ETC

Capacitor, 0.47 µF, ±20%, Z5U/X7R

Capacitor, 10 pF, ±5%, COG

Capacitor, 33 nF, ±5%, COG

Ferrite bead, 2.5 k/100 MHz

RF transistor, 2SC9018.

Resistor, 100 k, ±5%

Q1

R34

R41

R32

Venkel

Resistor, 120 k, ±5%

Resistor, 10 , ±5%

Rev. 0.3

17

AN602

Table 8. Si4822/26/40/44 Application Circuits: Slide Switch Select Band and MCU Re-define Band

Property (Continued)

R31

Venkel

Resistor, 1 k, ±5%

R9-12, R14-15,

R35

Band switching resistor, 20 k, ±1%

R8

Venkel

Band switching resistor, 50 k, ±1%

Optional

C28, C29

Y1

Crystal load capacitor, 22 pF, ±5%, COG (Optional: for crystal

oscillator option)

Murata

Epson

32.768 kHz crystal (Optional: for crystal oscillator option)

Table 9. Si4822/26/40/44 Application Circuits: Slide Switch Select Band and Use Default Band

Property

Component(s)

Value/Description

Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R

Capacitor, 0.47 µF, ±20%, Z5U/X7R

RF coupling capacitors, 33 pF, ±5%, COG

Capacitor 4.7 µF, ±20%, Z5U/X7R

Capacitor 47 µF, ±20%, Z5U/X7R

Resistor, 100 , ±5%

Supplier

C1,C6,C19

Murata

C5

C34

Murata

C4,C7,C15

C13

Murata

R27

Venkel

R6

Venkel

Resistor, 100 k, ±5%

R3, R42

R7,R33

R28

Venkel

Resistor, 10 k, ±5%

Venkel

Band switching resistor, 20 k, ±1%

Band switching resistor, 40 k, ±1%

Band switching resistor, 120 k, ±1%

Band switching resistor, 47 k, ±1%

Band switching resistor, 30 k, ±1%

Band switching resistor, 33 k, ±1%

Venkel

R29

Venkel

R44

Venkel

R43

Venkel

R36

Venkel

U1

Silicon Laboratories

Si4822/26/40/44 AM/FM/SW Analog Tune Digital Display Radio

Tuner

L2

Murata

Jiaxin Electronics

Various

Inductor 270 nH

MW ferrite antenna 220 µH

Whip antenna

ANT1

ANT2

18

Rev. 0.3

AN602

Table 9. Si4822/26/40/44 Application Circuits: Slide Switch Select Band and Use Default Band

Property (Continued)

Component(s)

Value/Description

Variable resistor (POT), 100 k, ±10%

Slide switch

Supplier

VR1

Changtaier

S2

Shengda

Si4826/44 Only

C36

C33

C30-31

B6

Murata

ETC

Capacitor, 0.47 µF, ±20%, Z5U/X7R

Capacitor, 10 pF, ±5%, COG

Capacitor, 33 nF, ±5%, COG

Ferrite bead, 2.5 k/100 MHz

RF transistor, 2SC9018

Resistor, 100 k, ±5%

Q1

R34

R41

R32

R31

Venkel

Resistor, 120 k, ±5%

Resistor, 10 , ±5%

Resistor, 1 k, ±5%

R9-12, R14-15,

R35

Band switching resistor, 20 k, ±1%

R8

Venkel

Band switching resistor, 50 k, ±1%

Optional

C28, C29

Y1

Crystal load capacitor, 22 pF, ±5%, COG (Optional: for crystal

oscillator option)

Murata

Epson

32.768 kHz crystal (Optional: for crystal oscillator option)

Rev. 0.3

19

AN602

Table 10. Si4827 Application Circuit: MCU Select Band

Component(s)

C1,C6,C19

C5,C36

C34

Value/Description

Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R

Capacitor, 0.47 µF, ±20%, Z5U/X7R

RF coupling capacitors, 33 pF, ±5%, COG

Capacitor 4.7 µF, ±20%, Z5U/X7R

Capacitor 47 µF, ±20%, Z5U/X7R

Resistor, 100 , ±5%

Supplier

Murata

C7,C15

C13

Murata

R27

Venkel

R6 R34

R3

Resistor, 100 k, ±5%

Venkel

Resistor, 10 k, ±5%

Venkel

U1

Si4827-A AM/FM/SW Analog Tune Digital Display Radio Tuner

Inductor 270 nH

Silicon Laboratories

Murata

L2

ANT1

ANT2

VR1

MW ferrite antenna 220 µH

Whip antenna

Jiaxin Electronics

Various

Variable resistor (POT), 100 k, ±10%

Capacitor, 10 pF, ±5%, COG

Capacitor, 33 nF, ±5%, COG

Ferrite bead,2.5k/100 MHz

RF transistor, 2SC9018

Changtaier

Murata

C33

C30-31

B6

Murata

Q1

ETC

R41

Resistor, 120 k, ±5%

Venkel

R32

Resistor, 10 , ±5%

Venkel

R31

Resistor, 1 k, ±5%

Venkel

Optional

C28, C29

Y1

Crystal load capacitors, 22 pF, ±5%, COG (Optional: for crystal

oscillator option)

Murata

Epson

32.768 kHz crystal (Optional: for crystal oscillator option)

20

Rev. 0.3

AN602

Table 11. Si4827 Application Circuit: Slide Switch Select Band

Component(s)

C1,C6,C19

C5,C36

C34

Value/Description

Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R

Capacitor, 0.47 µF, ±20%, Z5U/X7R

RF coupling capacitors, 33 pF, ±5%, COG

Capacitor 4.7 µF, ±20%, Z5U/X7R

Capacitor 47 µF, ±20%, Z5U/X7R

Resistor, 100 , ±5%

Supplier

Murata

Venkel

C7,C15

C13

R27

R6 R34

R3

Resistor, 100 k, ±5%

Resistor, 10 k, ±5%

U1

Si4827-A AM/FM/SW Analog Tune Digital Display Radio Tuner

Silicon Laboratories

L2

ANT1

ANT2

VR1

C33

Inductor 270 nH

Murata

Jiaxin Electronics

Various

MW ferrite antenna 220 µH

Whip antenna

Variable resistor (POT), 100 k, ±10%

Capacitor, 10 pF, ±5%, COG

Capacitor, 33 nF, ±5%, COG

Ferrite bead, 2.5 k/100 MHz

RF transistor, 2SC9018

Resistor, 120 k, ±5%

Resistor, 10 , ±5%

Changtaier

Murata

C30-31

B6

Murata

Q1

ETC

R41

Venkel

R32

Venkel

R31

Resistor, 1 k, ±5%

Venkel

Optional

C28, C29

Y1

Crystal load capacitors, 22 pF, ±5%, COG (Optional: for crystal

oscillator option)

Murata

Epson

32.768 kHz crystal (Optional: for crystal oscillator option)

Rev. 0.3

21

AN602

3.8. Si4822/26/27/40/44 PCB Layout Guidelines

1-layer PCB is used for Si4822/26/27/40/44

GND routed by large plane

Power routed with traces

0402 component size or larger

10 mil traces width

20 mil trace spacing

15 mil component spacing

Keep the AM ferrite loop at least 5 cm away from the tuner chip (recommended)

Keep the AM ferrite loop antenna away from the MCU, audio amp, and other circuits which have AM

interference

Place V

/V

bypass capacitor C6, C15 as close as possible to the supply (pin20/pin 21) and DBYP (pin 22).

DD1 DD2

Do not connect the DBYP (pin 22) to the board GND.

Place the crystal as close to XTALO (pin18) and XTALI (pin19) as possible, and make the loop area of XTALO

trace and XTALI trace as small as possible.

Route all GND (including RFGND) pins to the GND plane underneath the chip. Try to create a large GND plane

underneath and around the chip.

Do not route Pin 6 and 7. These pins must be left floating to guarantee proper operation.

Keep the Tune1 and Tune2 traces away from pin 6 and pin 7, route Tune1 and Tune2 traces in parallel and the

same way.

Place C1, C13 as close to pin3 TUNE1 as possible.

For Si4822/26, do not route pin 23, leave it floating to guarantee proper operation.

Try to refer to the Si4840/44 PCB Layout example as much as possible when doing Si4822/26/27 PCB layout.

Figure 10. Si4840/44 PCB Layout Example

22

Rev. 0.3

AN602

4. Headphone Antenna for FM Receive

The Si4822/26/27/40/44 FM Receiver component supports a headphone antenna interface through the FMI pin. A

headphone antenna with a length between 1.1 and 1.45 m suits the FM application very well because it is

approximately half the FM wavelength (FM wavelength is ~3 m).

4.1. Headphone Antenna Design

A typical headphone cable will contain three or more conductors. The left and right audio channels are driven by a

headphone amplifier onto left and right audio conductors and the common audio conductor is used for the audio

return path and FM antenna. Additional conductors may be used for microphone audio, switching, or other

functions, and in some applications the FM antenna will be a separate conductor within the cable. A representation

of a typical application is shown in Figure 11.

Figure 11. Typical Headphone Antenna Application

Rev. 0.3

23

AN602

4.2. Headphone Antenna Schematic

Figure 12. Headphone Antenna Schematic

The headphone antenna implementation requires components L

, C4, F1, and F2 for a minimal

MATCH

implementation. The ESD protection diodes and headphone amplifier components are system components that will

be required for proper implementation of any tuner.

Inductor L

is selected to maximize the voltage gain across the FM band. L

should be selected with a Q

MATCH

of 15 or greater at 100 MHz and minimal dc resistance.

AC-coupling capacitor C4 is used to remove a dc offset on the FMI input. This capacitor must be chosen to be large

enough to cause negligible loss with an LNA input capacitance of 4 to 6 pF. The recommended value is 100 pF to

1 nF.

Ferrite beads F1 and F2 provide a low-impedance audio path and high-impedance RF path between the

headphone amplifier and the headphone. Ferrite beads should be placed on each antenna conductor connected to

nodes other than the FMIP, such as left and right audio, microphone audio, switching, etc. In the example shown in

Figure 12, these nodes are the left and right audio conductors. Ferrite beads should be 2.5 k or greater at

100 MHz, such as the Murata BLM18BD252SN1. High resistance at 100 MHz is desirable to maximize R

SHUNT

and, therefore, R . Refer to “AN383: Si47xxAntenna, Schematic, and Layout Guidelines”, Appendix A, for a

P

complete description of R

, R , etc.

SHUNT

P

ESD diodes D1, D2, and D3 are recommended if design requirements exceed the ESD rating of the headphone

amplifier and the Si4822/26/40/44. Diodes should be chosen with no more than 1 pF parasitic capacitance, such as

the California Micro Devices CM1210. Diode capacitance should be minimized to minimize C

and, therefore,

SHUNT

C . If D1 and D2 must be chosen with a capacitance greater than 1 pF, they should be placed between the ferrite

P

beads F1 and F2 and the headphone amplifier to minimize C

. This placement will, however, reduce the

SHUNT

effectiveness of the ESD protection devices. Diode D3 may not be relocated and must therefore have a

capacitance less than 1 pF. Note that each diode package contains two devices to protect against positive and

negative polarity ESD events.

C9 and C10 are 125 µF ac coupling capacitors required when the audio amplifier does not have a common mode

output voltage and the audio output is swinging above and below ground.

Optional bleed resistors R5 and R6 may be desirable to discharge the ac-coupling capacitors when the headphone

cable is removed.

24

Rev. 0.3

AN602

Optional RF shunt capacitors C5 and C6 may be placed on the left and right audio traces at the headphone

amplifier output to reduce the level of digital noise passed to the antenna. The recommended value is 100 pF or

greater; however, the designer should confirm that the headphone amplifier is capable of driving the selected shunt

capacitance.

This schematic example uses the National Semiconductor LM4910 headphone amplifier. Passive components R1-

R4 and C7-C8 are required for the LM4910 headphone amplifier as described in the LM4910 data sheet. The gain

of the right and left amplifiers is -R3/R1 and -R4/R2, respectively. These gains can be adjusted by changing the

values of resistors R3 and R4. As a general guide, gain between 0.6 and 1.0 is recommended for the headphone

amplifier, depending on the gain of the headphone elements. Capacitors C7 and C8 are ac-coupling capacitors

required for the LM4910 interface. These capacitors, in conjunction with resistors R1 and R2, create a high-pass

filter that sets the audio amplifier's lower frequency limit. The high-pass corner frequencies for the right and left

amplifiers are:

1

-----------------------------------

f_CRIGHT

=

, f_CLEFT= -----------------------------------

2  R1  C7

2  R2  C8

With the specified BOM components, the corner frequency of the headphone amplifier is approximately 20 Hz.

Capacitor C1 is the supply bypass capacitor for the audio amplifier. The LM4910 can also be shut down by

applying a logic low voltage to the number 3 pin. The maximum logic low level is 0.4 V and the minimum logic high

level is 1.5 V.

The bill of materials for the typical application schematic shown in Figure 12 is provided in Table 12. Note that

manufacturer is not critical for resistors and capacitors.

4.3. Headphone Antenna Bill of Materials

Table 12. Headphone Antenna Bill of Materials

Designator

LMATCH

C4

Description

IND, 0603, SM, 270 nH, MURATA, LQW18ANR27J00D

AC coupling cap, SM, 0402, X7R, 100 pF

IC, SM, ESD DIODE, SOT23-3, California Micro Devices, CM1210-01ST

IC, SM, HEADPHONE AMP, National Semiconductor, LM4910MA

RES, SM, 0603, 20 k

D1, D2, D3

U3

R1, R2, R3, R4

C7, C8

C5, C6

R5, R6

F1, F2

CAP, SM, 0603, 0.39UF, X7R

CAP, SM, 0402, C0G, 100 pF

RES, SM, 0603, 100 k

FERRITE BEAD, SM, 0603, 2.5 k, Murata, BLM18BD252SN1D

CAP, SM, 0402, X7R, 0.1 µF

C1

R7

RES, SM, 0402, 10 k

Rev. 0.3

25

AN602

4.4. Headphone Antenna Layout

To minimize inductive and capacitive coupling, inductor L

and headphone jack J24 should be placed together

MATCH

and as far from noise sources such as clocks and digital circuits as possible. L

headphone connector to keep audio currents away from the chip.

should be placed near the

MATCH

To minimize C

and C , place ferrite beads F1 and F2 as close as possible to the headphone connector.

P

SHUNT

To maximize ESD protection diode effectiveness, place diodes D1, D2, and D3 as close as possible to the

headphone connector. If capacitance larger than 1 pF is required for D1 and D2, both components should be

placed between FB1 and FB2 and the headphone amplifier to minimize C

.

SHUNT

Place the chip as close as possible to the headphone connector to minimize antenna trace capacitance,

CPCBANT. Keep the trace length short and narrow and as far above the reference plane as possible, restrict the

trace to a microstrip topology (trace routes on the top or bottom PCB layers only), minimize trace vias, and relieve

ground fill on the trace layer. Note that minimizing capacitance has the effect of maximizing characteristic

impedance. It is not necessary to design for 50  transmission lines.

To reduce the level of digital noise passed to the antenna, RF shunt capacitors C5 and C6 may be placed on the

left and right audio traces close to the headphone amplifier audio output pins. The recommended value is 100 pF

or greater, however, the designer should confirm that the headphone amplifier is capable of driving the selected

shunt capacitance.

4.5. Headphone Antenna Design Checklist

Select an antenna length of 1.1 to 1.45 m.

Select matching inductor L

to maximize signal strength across the FM band.

MATCH

with a Q of 15 or greater at 100 MHz and minimal dc resistance.

Place inductor L

and headphone connector together and as far from potential noise sources as

MATCH

possible to reduce capacitive and inductive coupling.

Place the chip close to the headphone connector to minimize antenna trace length. Minimizing trace length

reduces CP and the possibility for inductive and capacitive coupling into the antenna by noise sources.

This recommendation must be followed for optimal device performance.

Select ferrite beads F1-F2 with 2.5 k or greater resistance at 100 MHz to maximize RSHUNT and,

therefore, RP.

Place ferrite beads F1-F2 close to the headphone connector.

Select ESD diodes D1-D3 with minimum capacitance.

Place ESD diodes D1-D3 as close as possible to the headphone connector for maximum effectiveness.

Place optional RF shunt capacitors near the headphone amplifier’s left and right audio output pins to

reduce the level of digital noise passed to the antenna.

26

Rev. 0.3

AN602

5. Whip Antenna for FM Receiver

A whip antenna is a typical monopole antenna.

5.1. FM Whip Antenna Design

A whip antenna is a monopole antenna with a stiff but flexible wire mounted vertically with one end adjacent to the

ground plane.

There are various types of whip antennas including long non-telescopic metal whip antennas, telescopic metal

whip antennas, and rubber whip antennas. Figure 13 shows the telescopic whip antenna.

Figure 13. Telescopic Whip Antennas

The whip antenna is capacitive, and its output capacitance depends on the length of the antenna (maximum length

~56 cm). At 56 cm length, the capacitance of the whip antenna ranges from 18 to 32 pF for the US FM band. The

antenna capacitance is about 22 pF in the center of the US FM band (98 MHz).

5.2. FM Whip Antenna Schematic

Figure 14. FM Whip Antenna Schematic

L1 (56 nH) is the matching inductor and it combines with the antenna impedance and the FMI impedance to

resonate in the FM band.

C5 (1 nF) is the ac coupling cap going to the FMI pin.

U3 is a required ESD diode since the antenna is exposed. The diode should be chosen with no more than 1 pF

parasitic capacitance, such as the California Micro Device CM1213.

Rev. 0.3

27

AN602

5.3. FM Whip Antenna Bill of Materials

Table 13. FM Whip Antenna Bill of Materials

Designator

WIP_ANTENNA

L1

Description

Whip Antenna

Tuning Inductor, 0603, SM, 56 nH,

MURATA, LQW18AN56nJ00D

C5

U3

AC coupling capacitor,

1 nF, 10%, COG

IC, SM, ESD DIODE, SOT23-3, California

Micro Devices, CM1213-01ST

5.4. FM Whip Antenna Layout

Place the chip as close as possible to the whip antenna. This will minimize the trace length between the device and

whip antenna which in turn will minimize parasitic capacitance and the possibility of noise coupling. Place inductor

L1 and the antenna connector together and as far from potential noise sources as possible. Place the ac coupling

capacitor C5 as close to the FMI pin as possible. Place ESD diode U3 as close as possible to the whip antenna

input connector for maximum effectiveness.

5.5. FM Whip Antenna Design Checklist

Maximize whip antenna length for optimal performance.

Select matching inductor L1 with a Q of 15 or greater at 100 MHz and minimal dc resistance.

Select L1 inductor value to maximize resonance gain from FM frequency (64 MHz) to FM frequency

(109 MHz).

Place L1 and whip antenna close together and as far from potential noise sources as possible to reduce

capacitive and inductive coupling.

Place the chip as close as possible to the whip antenna to minimize the antenna trace length. This reduces

parasitic capacitance and hence reduces coupling into the antenna by noise sources. This

recommendation must be followed for optimal device performance.

Place ESD U3 as close as possible to the whip antenna for maximum effectiveness.

Select ESD diode U3 with minimum capacitance.

Place the ac coupling capacitor, C5, as close to the FMI pin as possible.

28

Rev. 0.3

AN602

6. Ferrite Loop Antenna for AM Receive

There are two types of antennas that will work well for an AM receiver: a ferrite loop antenna or an air loop

antenna. A ferrite loop antenna can be placed internally on the device or externally to the device with a wire

connection. When the ferrite loop antenna is placed internally on the device, it is more susceptible to picking up

any noise within the device. When the ferrite loop antenna is placed outside a device, e.g., at the end of an

extension cable, it is less prone to device noise activity and may result in better AM reception.

6.1. Ferrite Loop Antenna Design

Figure 15 shows an example of ferrite loop antennas. The left figure is the standard size ferrite loop antenna. It is

usually used in products with a lot of space, such as desktop radios. The right figure is the miniature size of the

loop antenna. It is usually used in small products where space is at a premium, such as cell phones. If possible,

use the standard size ferrite loop antenna as it has a better sensitivity than the miniature one.

Figure 15. Standard and Miniature Ferrite Loop Antennas

A loop antenna with a ferrite inside should be designed such that the inductance of the ferrite loop is between 180

and 450 µH for the Si4822/26/27/40/44 AM Receiver.

Table 14 lists the recommended ferrite loop antenna for the Si4822/26/27/40/44 AM Receiver.

Table 14. Recommended Ferrite Loop Antenna

Part #

Diameter

8 mm

Length

50 mm

30 mm

Turns

70

Ui

Type

Mn-Zn

Ni-Zn

Application

SL8X50MW70T

SL4X30MW100T

400

300

Desktop Radios

4 mm

100

Portable Radios (MP3,

Cell, GPS)

SL3X30MW105T

SL3X25MW100T

SL5X7X100MW70T

3 mm

30 mm

25 mm

100 mm

105

110

70

300

400

Ni-Zn

Ni-An

Mn-Zn

5 x 7 mm

Desktop Radios

The following is the vendor information for the ferrite loop antennas:

Jiaxin Electronics

Shenzhen Sales Office

email:

Web:

sales@firstantenna.com

www.firstantenna.com

Rev. 0.3

29

AN602

6.2. Ferrite Loop Antenna Schematic

Figure 16. AM Ferrite Loop Antenna Schematic

C1 is the ac coupling cap going to the AMI pin and its value should be 0.47 µF.

D1 is an optional ESD diode if there is an exposed pad going to the AMI pin.

6.3. Ferrite Loop Antenna Bill of Materials

Table 15. Ferrite Loop Antenna Bill of Materials

Designator

ANT1

Description

Note

Ferrite loop antenna, 180~450 µH

AC coupling capacitor, 0.47 µF, 10%, Z5U/X7R

C1

D1

ESD diode, IC, SM, SOT23-3,

California Micro Devices, CM1213-01ST

Optional; only needed if there is any

exposed pad going to the AMI pin.

30

Rev. 0.3

AN602

6.4. Ferrite Loop Antenna Layout

Place the chip as close as possible to the ferrite loop antenna feedline. This will minimize the trace going to the

ferrite antenna, which in turn will minimize parasitic capacitance and also will minimize the possibility of noise

sources coupling to the trace.

The placement of the AM antenna is critical, since AM is susceptible to noise sources causing interference in the

AM band. Noise sources can come from clock signals, switching power supply, and digital activities (e.g., MCU).

When the AM input is interfaced to a ferrite loop stick antenna, the placement of the ferrite loop stick antenna is

critical to minimize inductive coupling. Place the ferrite loop stick antenna as far away from interference sources as

possible. In particular, make sure the ferrite loop stick antenna is away from signals on the PCB and away from

even the I/O signals of the chip. Do not route any signal under or near the ferrite loop stick. Route digital traces in

between ground plane for best performance. If that is not possible, route digital traces on the opposite side of the

chip. This will minimize capacitive coupling between the plane(s) and the antenna.

To tune correctly, the total capacitance seen at the AMI input needs to be minimized and kept under a certain value.

The total acceptable capacitance depends on the inductance seen by the chip at its AM input. The acceptable

capacitance at the AM input can be calculated using the formula shown in Equation 2

1

C_Total= --------------------------------------------------

2f_max²L_effective

Equation 2. Expected Total Capacitance at AMI

Where:

C

= Total capacitance at the AMI input

Total

L

= Effective inductance at the AMI input

effective

f

= Highest frequency in AM band

max

The total allowable capacitance, when interfacing a ferrite loop stick antenna, is the effective capacitance resulting

from the AMI input pin, the capacitance from the PCB, and the capacitance from the ferrite loop stick antenna. The

inductance seen at the AMI in this case is primarily the inductance of the ferrite loop stick antenna. The total

allowable capacitance in the case of an air loop antenna is the effective capacitance resulting from the AMI input

pin, the capacitance of the PCB, the capacitance of the transformer, and the capacitance of the air loop antenna.

The inductance in this case should also take all the elements of the circuit into account. The input capacitance of

the AMI input is 8 pF. The formula shown in Equation 2 gives a total capacitance of 28 pF when a 300 µH ferrite

loop stick antenna is used for an AM band with 10 kHz spacing, where the highest frequency in the band is

1750 kHz.

6.5. Ferrite Loop Antenna Design Checklist

Place the chip as close as possible to the ferrite loop antenna feedline to minimize parasitic capacitance

and the possibility of noise coupling.

Place the ferrite loop stick antenna away from any sources of interference and even away from the I/O

signals of the chip. Please make sure that the AM antenna is as far away as possible from circuits that

switch at a rate which falls in the AM band (504–1750 kHz).

Keep the AM ferrite loop antenna at least 5 cm away from the tuner chip (recommended).

Place optional component D1 if the antenna is exposed.

Select ESD diode D1 with minimum capacitance.

Do Not Place any ground plane under the ferrite loop stick antenna if the ferrite loop stick antenna is

mounted on the PCB. The recommended ground separation is 1/4 inch or the width of the ferrite.

Route traces from the ferrite loop stick connectors to the AMI input via the ac coupling cap C1 such that

the capacitance from the traces and the pads is minimized.

Rev. 0.3

31

AN602

7. Air Loop Antenna for AM

An air loop antenna is an external AM antenna (because of its large size) typically found on home audio

equipment. An air loop antenna is placed external to the product enclosure making it more immune to system noise

sources. It also will have a better sensitivity compared to a ferrite loop antenna.

7.1. Air Loop Antenna Design

Figure 17 shows an example of an air loop antenna.

Figure 17. Air Loop Antenna

Unlike a ferrite loop, an air loop antenna will have a smaller equivalent inductance because of the absence of ferrite

material. A typical inductance is on the order of 10 to 20 µH. Therefore, in order to interface with the air loop

antenna properly, a transformer is required to raise the inductance into the 180 to 450 µH range.

T1 is the transformer to raise the inductance to within 180 to 450 µH range. A simple formula to use is as follows:

L_equivalent= N²L_AIRLOOP

Equation 3.

Typically, a transformer with a turn ratio of 1:5 to 1:7 is good for an air loop antenna of 10 to 20 µH to bring the

inductance within the 180 to 450 µH range.

Choose a high-Q transformer with a coupling coefficient as close to 1 as possible and use a multiple strands Litz

wire for the transformer winding to reduce the skin effect. All of this will ensure that the transformer will be a low

loss transformer.

Finally, consider using a shielded enclosure to house the transformer or a toroidal shape core to prevent noise

pickup from interfering sources. A few recommended transformers are listed in Table 16.

32

Rev. 0.3

AN602

Table 16. Recommended Transformers

Transformer 1

Jiaxin Electronics

SL9x5x4MWTF1

Surface Mount

12T

Transformer 2

UMEC

Transformer 3

Vendor

Part Number

UMEC

TG-UTB01526

Through Hole

10T

TG-UTB01527S

Surface Mount

10T

Type

Primary Coil Turns (L1)

Secondary Coil Turns (L2)

Wire Gauge

70T

55T

58T

ULSA / 0.07 mm x 3

n/a

Inductance (L2)

380 µH ±10% @

796 kHz

184 µH min, 245 µH typ

@ 100 kHz

179 µH min, 263 µH typ

@ 100 kHz

Q

130

50

75

The following is the vendor information for the above transformer:

Vendor #1:

Jiaxin Electronics

Shenzhen Sales Office

email:

sales@firstantenna.com

www.firstantenna.com

Web:

Vendor #2:

UMEC USA, Inc.

Website: www.umec-usa.com

www.umec.com.tw

Rev. 0.3

33

AN602

7.2. Air Loop Antenna Schematic

Figure 18. AM Air Loop Antenna Schematic

C1 is the ac coupling cap going to the AMI pin and its value should be 0.47 µF.

D1 is a required ESD diode since the antenna is exposed.

7.3. Air Loop Antenna Bill of Materials

Table 17. Air Loop Antenna Bill of Materials

Designator

LOOP_ANTENNA

T1

Description

Air loop antenna

Transformer, 1:6 turns ratio

C1

D1

AC coupling capacitor, 0.47 µF, 10%, Z5U/X7R

ESD diode, IC, SM, SOT23-3,

California Micro Devices, CM1213-01ST

7.4. Air Loop Antenna Layout

Place the chip and the transformer as close as possible to the air loop antenna feedline. This will minimize the

trace going to the air loop antenna, which in turn will minimize parasitic capacitance and the possibility of noise

coupling.

When an air loop antenna with a transformer is used with the Si4822/26/27/40/44, minimize inductive coupling by

making sure that the transformer is placed away from all sources of interference. Keep the transformer away from

signals on the PCB and away from even the I/O signals of the Si4822/26/27/40/44. Do not route any signals under

or near the transformer. Use a shielded transformer if possible.

7.5. Air Loop Antenna Design Checklist

Select a shielded transformer or a toroidal shape transformer to prevent noise pickup from interfering

sources

Select a high-Q transformer with coupling coefficient as close to 1 as possible

Use multiple strands Litz wire for the transformer winding

Place the transformer away from any sources of interference and even away from the I/O signals of the

chip. Ensure that the AM antenna is as far away as possible from circuits that switch at a rate which falls in

the AM band (504 to 1750 kHz).

Route traces from the transformer to the AMI input via the ac coupling cap C1 such that the capacitance

from the traces and the pads is minimized.

Select ESD diode D1 with minimum capacitance.

34

Rev. 0.3

AN602

8. Whip Antenna for SW Receiver

SW reception usually uses whip antennas, the same as FM.

8.1. SW Whip Antenna Design

A whip antenna is a monopole antenna with a stiff but flexible wire mounted vertically with one end adjacent to the

ground plane.

Figure 19 shows the telescopic whip antenna.

Figure 19. Telescopic Whip Antenna for SW

8.2. SW Whip Antenna Schematic

Figure 20. SW Whip Antenna Schematic

Q1 2SC9018 is a low noise RF transistor and it constitutes a LNA to amplify the SW signal coming from the whip

antenna.

C30 (33 nF) is the ac coupling cap between whip antenna and LNA input.

C33 (0.47 µF) is the ac coupling cap going to the AMI pin.

R31, R41 are bias resistors of the transistor.

Rev. 0.3

35

AN602

8.3. SW Whip Antenna Bill of Materials

Table 18. SW Whip Antenna Bill of Materials

Designator

Description

Whip Antenna

WHIP_ANTENNA

Q1

Low noise RF transistor, 2SC9018

C30

AC coupling capacitor,

33 nF, 10%, COG

C33

R31

R41

Coupling capacitor, 0.47 µF, ±20%, Z5U/X7R

Resistor, 1 k, ±5%

Resistor, 200 k, ±5%

8.4. SW Whip Antenna Layout

Place the chip and 2SC9018 as close as possible to the whip antenna feedline. This will minimize the trace going

to the whip antenna, which in turn will minimize parasitic capacitance and also will minimize the possibility of noise

sources coupling to the trace.

8.5. SW Whip Antenna Design Checklist

Maximize whip antenna length for optimal performance.

Place Q1 and whip antenna close together and as far from potential noise sources as possible to reduce

capacitive and inductive coupling.

Place the chip as close as possible to the whip antenna to minimize the antenna trace length. This reduces

parasitic capacitance and hence reduces coupling into the antenna by noise sources. This

recommendation must be followed for optimal device performance.

Place the ac coupling capacitor C33, as close to the AMI pin as possible.

36

Rev. 0.3

AN602

DOCUMENT CHANGE LIST

Revision 0.2 to Revision 0.3

 Updated "1.Introduction"

 Updated "2.Si4822/26/27/40/44 Default Frequency

Band Definition and Selection"

 Added "3.5 Si4827 application circuit: Host MCU

select radio band"

 Added "3.6 Si4827 application circuit: Slide switch

select radio band"

 Added "Table10.Si44827 application circuit: Host

MCU select radio band"

 Added "Table11. Si4827 application circuit: Slide

switch select radio band"

Rev. 0.3

37

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型号：	SI4826
厂家：	SILICON
描述：	Si4822/26/27/40/44 ANTENNA, SCHEMATIC, LAYOUT, AND DESIGN GUIDELINES
文件：	总38页 (文件大小：1671K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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