AN602: Si4822/26/27/40/44 Antenna, Schematic, Layout, and Design Guidelines

AN602: Si4822/26/27/40/44 Antenna, Schematic, Layout, and Design Guidelines
AN602
Si4822/26/27/40/44 A NTENNA , S CHEMATIC , L AYOUT ,
AND D E S I G N G UIDEL INES
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”.
†
Si4826
Entry level wheel-tuned digital display
AM/FM/SW Receiver, Mono audio
†
†
Si4827
Entry level wheel-tuned digital display
AM/FM/SW Receiver, wide FM/SW
band, Mono audio
†
†
Si4840
Wheel-tuned digital display AM/FM
Receiver, Stereo audio
†
†
Si4844
Wheel-tuned digital display AM/FM/
SW Receiver, wide FM/SW band, Stereo audio
†
†
Rev. 0.3 2/13
Headphone
Whip
Ferrite Loop
Air Loop
SW Receiver
SW Antenna

†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
†
Copyright © 2013 by Silicon Laboratories
Whip
Entry level wheel-tuned digital display
AM/FM Receiver, Mono audio
AM Antenna
AM Receiver
Si4822
FM Antenna
†General
Description
Function
†Part
Number
FM Receiver
Table 1. Part Selection Guide
†
AN602
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
2
Band
Number
Band
Name
Band Frequency
Range
De-emphasis (FM)
Channel Space (AM)
Stereo LED on
Conditions
(Only for Si4840/44)
Total R to GND
(k, 1%)
Band1
FM1
87–108 MHz
75 µs
Separation = 6 dB,
RSSI = 20
47
Band2
FM1
87–108 MHz
75 µs
Separation = 12 dB,
RSSI = 28
57
Band3
FM1
87–108 MHz
50 µs
Separation = 6dB,
RSSI = 20
67
Band4
FM1
87–108 MHz
50 µs
Separation = 12 dB,
RSSI = 28
77
Band5
FM2
86.5–109 MHz
75 µs
Separation = 6 dB,
RSSI = 20
87
Band6
FM2
86.5–109 MHz
75 µs
Separation = 12 dB,
RSSI = 28
97
Band7
FM2
86.5–109 MHz
50 µs
Separation = 6 dB,
RSSI = 20
107
Band8
FM2
86.5–109 MHz
50 µs
Separation = 12 dB,
RSSI = 28
117
Band9
FM3
87.3–108.25 MHz
75 µs
Separation = 6 dB,
RSSI = 20
127
Rev. 0.3
AN602
Table 2. Band Sequence Definition (Continued)
Band
Number
Band
Name
Band Frequency
Range
De-emphasis (FM)
Channel Space (AM)
Stereo LED on
Conditions
(Only for Si4840/44)
Total R to GND
(k, 1%)
Band10
FM3
87.3–108.25 MHz
50 µs
Separation = 12 dB,
RSSI = 28
137
Band11
FM3
87.3–108.25 MHz
75 µs
Separation = 6 dB,
RSSI = 20
147
Band12
FM3
87.3–108.25 MHz
50 µs
Separation = 12 dB,
RSSI = 28
157
Band13
FM4
76–90 MHz
75 µs
Separation = 6 dB,
RSSI = 20
167
Band14
FM4
76–90 MHz
75 µs
Separation = 12 dB,
RSSI = 28
177
Band15
FM4
76–90 MHz
50 µs
Separation = 6 dB,
RSSI = 20
187
Band16
FM4
76–90 MHz
50 µs
Separation = 12 dB,
RSSI = 28
197
Band17
FM5
64–87 MHz
75 µs
Separation = 6 dB,
RSSI = 20
207
Band18
FM5
64–87 MHz
75 µs
Separation = 12 dB,
RSSI = 28
217
Band19
FM5
64–87 MHz
50 µs
Separation = 6 dB,
RSSI = 20
227
Band20
FM5
64–87 MHz
50 µs
Separation = 12 dB,
RSSI = 28
237
Band21
AM1
520–1710 kHz
10 kHz
247
Band22
AM2
522–1620 kHz
9 kHz
257
Band23
AM3
504–1665 kHz
9 kHz
267
Band24
AM4
520–1730 kHz
10 kHz
277
Band25
AM5
510–1750 kHz
10 kHz
287
Band26
SW1
5.6–6.4 MHz
297
Band27
SW2
5.95–6.2 MHz
307
Band28
SW3
6.8–7.6 MHz
317
Band29
SW4
7.1–7.6 MHz
327
Band30
SW5
9.2–10 MHz
337
Rev. 0.3
3
AN602
Table 2. Band Sequence Definition (Continued)
Band
Number
Band
Name
Band Frequency
Range
De-emphasis (FM)
Channel Space (AM)
Stereo LED on
Conditions
(Only for Si4840/44)
Total R to GND
(k, 1%)
Band31
SW6
9.2–9.9 MHz
347
Band32
SW7
11.45–12.25 MHz
357
Band33
SW8
11.6–12.2 MHz
367
Band34
SW9
13.4–14.2 MHz
377
Band35
SW10
13.57–13.87 MHz
387
Band36
SW11
15–15.9 MHz
397
Band37
SW12
15.1–15.8 MHz
407
Band38
SW13
17.1–18 MHz
417
Band39
SW14
17.48–17.9 MHz
427
Band40
SW15
21.2–22 MHz
437
Band41
SW16
21.45–21.85 MHz
447
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
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.
Total
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)
R35
20k 1%
SW13 (17.1MHz - 18MHz)
R15
20k 1%
SW11 (15MHz - 15.9MHz)
R10
20k 1%
Si4826/27/44 only
SW9 (13.4MHz - 14.2MHz)
R12
20k 1%
S2
BAND
1
SW7(11.45MHz - 12.25MHz)
2
3
4
5
6
7
8
9
10
11
12
13
R11
20k 1%
SW5(9.2MHz - 10.0MHz)
R14
20k 1%
SW3(6.8MHz - 7.6MHz)
R9
20k 1%
SW1 (5.6MHz - 6.4MHz)
R8
50k 1%
AM1 (520kHz - 1710kHz)
R7
40k 1%
FM5 (64MHz - 87MHz)
R28
40k 1%
FM4 (76MHz - 90MHz)
R29
120k 1%
FM1 (87MHz - 108MHz)
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
Range
De-emphasis (FM)
Channel space (AM)
Stereo LED On
Conditions (Only
for Si4840/44)
Total R to GND
(k, 1%)
Band1
FM1
87–108 MHz
75 µs
Separation = 6 dB,
RSSI = 20
47
Band13
FM4
76–90 MHz
75 µs
Separation = 6 dB,
RSSI = 20
167
Band17
FM5
64–87 MHz
75 µs
Separation = 6 dB,
RSSI = 20
207
Band21
AM1
520–1710 kHz
10 kHz
Band26
SW1
5.6–6.4 MHz
297
Band28
SW3
6.8–7.6 MHz
317
Band30
SW5
9.2–10 MHz
337
Band32
SW7
11.45–12.25 MHz
357
Band34
SW9
13.4–14.2 MHz
377
Band36
SW11
15–15.9 MHz
397
Band38
SW13
17.1–18 MHz
417
Band40
SW15
21.2–22 MHz
437
247
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)
Channel space (AM)
Stereo LED On
Conditions (Only
for Si4840/44)
Total R to GND
(k, 1%)
Band4
FM1
87–108 MHz
50 µs
Separation = 12 dB,
RSSI = 28
77
Band22
AM2
522–1620 kHz
9 kHz
6
Rev. 0.3
257
AN602
TUNE1
R3
243k 1%
S2
BAND
1
AM
2
3
R4
180k 1%
FM
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
Channel space (AM)
Si4840/44)
Band2
FM1
87–108 MHz
75 µs
Band21
AM1
520–1710 kHz
10 kHz
Separation = 12 dB,
RSSI = 28
Total R to GND
(k, 1%)
57
247
TUNE1
R3
253k 1%
S2
BAND
1
2
AM
3
R4
190k 1%
FM
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 VCC directly
C6 & C15 are required bypass capacitors for VDD1/VDD2 power supply pin 20/21. Place C6/C15 as close as
possible to the VDD1/VDD2 pin 20/21 and DBYP pin 22. These recommendations are made to reduce the size of the
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
C36
0.47u
100R
R32
10R
C34
33p
C31
33n
2
3
4
5
6
7
8
9
10
11
12
1
LOUT/AOUT
Si4822/26/40/44
24
ROUT/NC
23
DBYP
22
VDD2
21
VDD1
20
19
XTALI
XTALO
18
SCLK
17
16
SDIO
U1
LNA_EN
IRQ
TUNE1
TUNE2
BAND
NC
NC
FMI
RFGND
NC
NC
RST
Q1
2SC9018
13
R34
100k
15
33n
C4
4.7u
C7
Si4826/44 only
4.7u
C19
0.1u
VCC
SDIO
LOUT
ROUT
(For Si4822/26, pin24 is AOUT)
(For Si4822/26, pin23 is NC)
VCC
VCC
R6
100k
C6
RESET
To host MCU
To host MCU
[1] LNA_EN
0.47u
AMI
B6
2.5k/100M
10p
GND
C30
C5
GND
R41
120k
14
[1]
IRQ
VCC
270nH
R31
1k
C33
ANT1
MW ferrite antenna
LNA_EN
L2
C15
0.1u 4.7u
R3
10k
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 VCC directly.
ANT2
TUNE1
FM/SW
VR1
100k 10%
C13
C1
47u
0.1u
VCC
R27
C36
0.47u
100R
R32
10R
C34
33p
C31
33n
2
3
4
5
6
7
8
9
VCC
1
LOUT/AOUT
Si4822/26/40/44
24
ROUT/NC
23
DBYP
22
VDD2
21
VDD1
20
XTALI
19
XTALO
18
17
SCLK
U1
LNA_EN
IRQ
TUNE1
TUNE2
BAND
NC
NC
FMI
11
10
NC
RFGND
SDIO
16
13
RST
Q1
2SC9018
R34
100k
15
33n
NC
AMI
12
[1] LNA_EN
0.47u
GND
2.5k/100M
10p
C30
14
B6
10k
C5
GND
R41
120k
R42
VCC
270nH
R31
1k
C33
[1]
ANT1
MW ferrite antenna
LNA_EN
To host MCU
IRQ
L2
C4
4.7u
C7
Si4826/44 only
4.7u
VCC
RESET
To host MCU
R6
ROUT
(For Si4822/26, pin24 is AOUT)
(For Si4822/26, pin23 is NC)
VCC
VCC
C19
0.1u
LOUT
100k
C6
C15
0.1u 4.7u
R3
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.
TUNE1 [1]
R36
33k 1%
R43
30k 1%
ANT2
[1] TUNE1
SW15 (21.2MHz - 22MHz)
VR1
100k 10%
FM/SW
C13
C1
47u
0.1u
R35
20k 1%
SW13 (17.1MHz - 18MHz)
VCC
R27
C36
0.47u
R32
10R
1
2
3
R12
20k 1%
S2
LOUT/AOUT
24
ROUT/NC
DBYP
23
22
VDD2
21
VDD1
20
XTALO
SCLK
XTALI
19
18
17
16
SDIO
U1
BAND [1]
Si4822/26/40/44
C4
4.7u
C7
Si4826/44 only
4.7u
R6
100k
C6
RESET
VCC
LOUT
ROUT
(For Si4822/26, pin24 is AOUT)
(For Si4822/26, pin23 is NC)
1
SW7(11.45MHz - 12.25MHz)
2
3
4
5
6
7
8
9
10
11
12
13
R11
20k 1%
SW5(9.2MHz - 10.0MHz)
R14
20k 1%
SW3(6.8MHz - 7.6MHz)
R9
20k 1%
VCC
VCC
C19
0.1u
To host MCU
SW11 (15MHz - 15.9MHz)
R10
20k 1%
SW9 (13.4MHz - 14.2MHz)
LNA_EN
IRQ
TUNE1
5
6
7
8
9
10
11
12
4
TUNE2
BAND
NC
NC
FMI
RFGND
NC
NC
AMI
14
13
GND
R34
100k
RST
Q1
2SC9018
15
33n
0.47u
GND
10p
C30
To host MCU
[1] LNA_EN
C5
ANT1
MW ferrite antenna
2.5k/100M
270nH
R31
1k
C33
[1]
IRQ
[1] BAND
L2
R41
120k
B6
Si4826/44 only
C34
33p
C31
33n
LNA_EN
R15
20k 1%
100R
C15
0.1u 4.7u
R3
SW1 (5.6MHz - 6.4MHz)
R8
50k 1%
AM1 (520kHz - 1710kHz)
10k
SDIO
R7
SCLK
20k 1%
Y1
FM5 (64MHz - 87MHz)
32.768KHz
C28
22p
R28
40k 1%
C29
22p
FM4 (76MHz - 90MHz)
R29
120k 1%
Optional
FM1 (87MHz - 108MHz)
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.
TUNE1 [1]
R36
33k 1%
R43
30k 1%
SW15 (21.2MHz - 22MHz)
ANT2
[1] TUNE1
FM/SW
R35
20k 1%
VR1
100k 10%
C13
C1
47u
0.1u
SW13 (17.1MHz - 18MHz)
VCC
C36
0.47u
100R
SW11 (15MHz - 15.9MHz)
C31
33n
1
ROUT/NC
DBYP
LOUT/AOUT
24
23
VDD2
22
21
VDD1
20
XTALI
19
SCLK
XTALO
18
17
16
RST
15
SDIO
U1
BAND [1]
Si4822/26/40/44
C4
4.7u
C7
Si4826/44 only
4.7u
C19
0.1u
VCC
VCC
R6
100k
VCC
RESET
To host MCU
S2
1
2
IRQ
LNA_EN
TUNE1
3
5
6
7
8
9
10
11
12
4
TUNE2
BAND
NC
NC
FMI
RFGND
NC
NC
AMI
13
GND
Q1
2SC9018
R34
100k
14
33n
R10
20k 1%
R12
20k 1%
[1] LNA_EN
GND
C30
10k
0.47u
ANT1
MW ferrite antenna
B6
R42
C5
10p
Si4826/44 only
To host MCU
SW9 (13.4MHz - 14.2MHz)
[1] BAND
L2
270nH
R31
1k
C33
[1]
R41
120k
2.5k/100M
IRQ
C34
33p
VCC
R32
10R
LNA_EN
R15
20k 1%
R27
C6
R3
C15
LOUT
ROUT
(For Si4822/26, pin24 is AOUT)
(For Si4822/26, pin23 is NC)
SW7(11.45MHz - 12.25MHz)
2
3
4
5
6
7
8
9
10
11
12
13
R11
20k 1%
SW5(9.2MHz - 10.0MHz)
R14
20k 1%
SW3(6.8MHz - 7.6MHz)
R9
20k 1%
SW1 (5.6MHz - 6.4MHz)
R8
50k 1%
0.1u 4.7u
AM1 (520kHz - 1710kHz)
10k
R7
SDIO
20k 1%
SCLK
FM5 (64MHz - 87MHz)
Y1
R28
40k 1%
32.768KHz
C28
22p
C29
22p
FM4(76MHz - 90MHz)
R29
120k 1%
FM1 (87MHz - 108MHz)
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 VCC
directly.
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)
C1,C6,C19
Value/Description
Supplier
Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R
Murata
C5
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
C34
RF coupling capacitors, 33 pF, ±5%, COG
Murata
C4,C7,C15
Capacitor 4.7 µF, ±20%, Z5U/X7R
Murata
C13
Capacitor 47 µF, ±20%, Z5U/X7R
Murata
R27
Resistor, 100 , ±5%
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
L2
Inductor 270 nH
ANT1
MW ferrite antenna 220 µH.
ANT2
Whip antenna
VR1
Silicon Laboratories
Murata
Jiaxin Electronics
Various
Variable resistor (POT), 100 k, ±10%
Changtaier
Si4826/44 Only
C36
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
C33
Capacitor, 10 pF, ±5%, COG
Murata
C30-31
Capacitor, 33 nF, ±5%, COG
Murata
B6
Ferrite bead,2.5 k/100 MHz.
Murata
Q1
RF transistor, 2SC9018.
R34
Resistor, 100 k, ±5%
Venkel
R41
Resistor, 120 k, ±5%
Venkel
R32
Resistor, 10 , ±5%
Venkel
R31
Resistor, 1 k, ±5%
Venkel
ETC
Optional
C28, C29
Y1
Crystal load capacitors, 22 pF, ±5%, COG (Optional: for crystal
oscillator option)
Murata
32.768 kHz crystal (Optional: for crystal oscillator option)
Epson
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
Value/Description
Supplier
Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R
Murata
C5
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
C34
RF coupling capacitors, 33 pF, ±5%, COG
Murata
C4,C7,C15
Capacitor 4.7 µF, ±20%, Z5U/X7R
Murata
C13
Capacitor 47 µF, ±20%, Z5U/X7R
Murata
R27
Resistor, 100 , ±5%
Venkel
R6
Resistor, 100 k, ±5%
Venkel
R3, R42
Resistor, 10 k, ±5%
Venkel
U1
Si4822/26/40/44 AM/FM/SW Analog Tune Digital Display Radio
Tuner
L2
Inductor 270 nH
ANT1
MW ferrite antenna 220 µH.
ANT2
Whip antenna
VR1
Silicon Laboratories
Murata
Jiaxin Electronics
Various
Variable resistor (POT), 100 k, ±10%
Changtaier
Si4826/44 Only
C36
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
C33
Capacitor, 10 pF, ±5%, COG
Murata
C30-31
Capacitor, 33 nF, ±5%, COG
Murata
B6
Ferrite bead, 2.5 k/100 MHz
Murata
Q1
RF transistor, 2SC9018.
R34
Resistor, 100 k, ±5%
Venkel
R41
Resistor, 120 k, ±5%
Venkel
R32
Resistor, 10 , ±5%
Venkel
R31
Resistor, 1 k, ±5%
Venkel
ETC
Optional
C28, C29
Y1
16
Crystal load capacitors, 22 pF, ±5%, COG
for crystal oscillator option)
(Optional:
32.768 kHz crystal (Optional: for crystal oscillator option)
Rev. 0.3
Murata
Epson
AN602
Table 8. Si4822/26/40/44 Application Circuits: Slide Switch Select Band and MCU Re-define Band
Property
Component(s)
Value/Description
Supplier
C1,C6,C19
Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R
Murata
C5
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
C34
RF coupling capacitors, 33 pF, ±5%, COG
Murata
C4,C7,C15
Capacitor 4.7 µF, ±20%, Z5U/X7R
Murata
C13
Capacitor 47 µF, ±20%, Z5U/X7R
Murata
R27
Resistor, 100 , ±5%
Venkel
R6
Resistor, 100 k, ±5%
Venkel
R3
Resistor, 10 k, ±5%
Venkel
R7,R33
Band switching resistor, 20 k, ±1%
Venkel
R28
Band switching resistor, 40 k, ±1%
Venkel
R29
Band switching resistor, 120 k, ±1%
Venkel
R44
Band switching resistor, 47 k, ±1%
Venkel
R43
Band switching resistor, 30 k, ±1%
Venkel
R36
Band switching resistor, 33 k, ±1%
Venkel
U1
Si4822/26/40/44 AM/FM/SW Analog Tune Digital Display Radio
Tuner
Silicon Laboratories
L2
Inductor 270 nH
Murata
ANT1
MW ferrite antenna 220 µH
Jiaxin Electronics
ANT2
Whip antenna
Various
VR1
Variable resistor (POT), 100 k, ±10%
Changtaier
S2
Slide switch
Shengda
Si4826/44 Only
C36
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
C33
Capacitor, 10 pF, ±5%, COG
Murata
C30-31
Capacitor, 33 nF, ±5%, COG
Murata
B6
Ferrite bead, 2.5 k/100 MHz
Murata
Q1
RF transistor, 2SC9018.
ETC
R34
Resistor, 100 k, ±5%
Venkel
R41
Resistor, 120 k, ±5%
Venkel
R32
Resistor, 10 , ±5%
Venkel
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
Resistor, 1 k, ±5%
Venkel
R9-12, R14-15,
R35
Band switching resistor, 20 k, ±1%
Venkel
R8
Band switching resistor, 50 k, ±1%
Venkel
Optional
C28, C29
Y1
Crystal load capacitor, 22 pF, ±5%, COG (Optional: for crystal
oscillator option)
Murata
32.768 kHz crystal (Optional: for crystal oscillator option)
Epson
Table 9. Si4822/26/40/44 Application Circuits: Slide Switch Select Band and Use Default Band
Property
Component(s)
Value/Description
Supplier
C1,C6,C19
Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R
Murata
C5
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
C34
RF coupling capacitors, 33 pF, ±5%, COG
Murata
C4,C7,C15
Capacitor 4.7 µF, ±20%, Z5U/X7R
Murata
C13
Capacitor 47 µF, ±20%, Z5U/X7R
Murata
R27
Resistor, 100 , ±5%
Venkel
R6
Resistor, 100 k, ±5%
Venkel
R3, R42
Resistor, 10 k, ±5%
Venkel
R7,R33
Band switching resistor, 20 k, ±1%
Venkel
R28
Band switching resistor, 40 k, ±1%
Venkel
R29
Band switching resistor, 120 k, ±1%
Venkel
R44
Band switching resistor, 47 k, ±1%
Venkel
R43
Band switching resistor, 30 k, ±1%
Venkel
R36
Band switching resistor, 33 k, ±1%
Venkel
U1
Si4822/26/40/44 AM/FM/SW Analog Tune Digital Display Radio
Tuner
Silicon Laboratories
L2
Inductor 270 nH
Murata
ANT1
MW ferrite antenna 220 µH
Jiaxin Electronics
ANT2
Whip antenna
Various
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
Supplier
VR1
Variable resistor (POT), 100 k, ±10%
Changtaier
S2
Slide switch
Shengda
Si4826/44 Only
C36
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
C33
Capacitor, 10 pF, ±5%, COG
Murata
C30-31
Capacitor, 33 nF, ±5%, COG
Murata
B6
Ferrite bead, 2.5 k/100 MHz
Murata
Q1
RF transistor, 2SC9018
ETC
R34
Resistor, 100 k, ±5%
Venkel
R41
Resistor, 120 k, ±5%
Venkel
R32
Resistor, 10 , ±5%
Venkel
R31
Resistor, 1 k, ±5%
Venkel
R9-12, R14-15,
R35
Band switching resistor, 20 k, ±1%
Venkel
R8
Band switching resistor, 50 k, ±1%
Venkel
Optional
C28, C29
Y1
Crystal load capacitor, 22 pF, ±5%, COG (Optional: for crystal
oscillator option)
Murata
32.768 kHz crystal (Optional: for crystal oscillator option)
Epson
Rev. 0.3
19
AN602
Table 10. Si4827 Application Circuit: MCU Select Band
Component(s)
C1,C6,C19
Value/Description
Supplier
Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R
Murata
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
RF coupling capacitors, 33 pF, ±5%, COG
Murata
C7,C15
Capacitor 4.7 µF, ±20%, Z5U/X7R
Murata
C13
Capacitor 47 µF, ±20%, Z5U/X7R
Murata
R27
Resistor, 100 , ±5%
Venkel
R6 R34
Resistor, 100 k, ±5%
Venkel
R3
Resistor, 10 k, ±5%
Venkel
U1
Si4827-A AM/FM/SW Analog Tune Digital Display Radio Tuner
L2
Inductor 270 nH
C5,C36
C34
ANT1
MW ferrite antenna 220 µH
ANT2
Whip antenna
Silicon Laboratories
Murata
Jiaxin Electronics
Various
VR1
Variable resistor (POT), 100 k, ±10%
Changtaier
C33
Capacitor, 10 pF, ±5%, COG
Murata
C30-31
Capacitor, 33 nF, ±5%, COG
Murata
B6
Ferrite bead,2.5k/100 MHz
Murata
Q1
RF transistor, 2SC9018
ETC
R41
Resistor, 120 k, ±5%
Venkel
R32
Resistor, 10 , ±5%
Venkel
R31
Resistor, 1 k, ±5%
Venkel
Optional
C28, C29
Y1
20
Crystal load capacitors, 22 pF, ±5%, COG (Optional: for crystal
oscillator option)
Murata
32.768 kHz crystal (Optional: for crystal oscillator option)
Epson
Rev. 0.3
AN602
Table 11. Si4827 Application Circuit: Slide Switch Select Band
Component(s)
C1,C6,C19
Value/Description
Supplier
Supply bypass capacitor, 0.1 µF, ±20%, Z5U/X7R
Murata
Capacitor, 0.47 µF, ±20%, Z5U/X7R
Murata
RF coupling capacitors, 33 pF, ±5%, COG
Murata
C7,C15
Capacitor 4.7 µF, ±20%, Z5U/X7R
Murata
C13
Capacitor 47 µF, ±20%, Z5U/X7R
Murata
R27
Resistor, 100 , ±5%
Venkel
R6 R34
Resistor, 100 k, ±5%
Venkel
R3
Resistor, 10 k, ±5%
Venkel
U1
Si4827-A AM/FM/SW Analog Tune Digital Display Radio Tuner
L2
Inductor 270 nH
C5,C36
C34
ANT1
MW ferrite antenna 220 µH
ANT2
Whip antenna
Silicon Laboratories
Murata
Jiaxin Electronics
Various
VR1
Variable resistor (POT), 100 k, ±10%
C33
Capacitor, 10 pF, ±5%, COG
Murata
C30-31
Capacitor, 33 nF, ±5%, COG
Murata
B6
Ferrite bead, 2.5 k/100 MHz
Murata
Q1
RF transistor, 2SC9018
ETC
R41
Resistor, 120 k, ±5%
Venkel
R32
Resistor, 10 , ±5%
Venkel
R31
Resistor, 1 k, ±5%
Venkel
Changtaier
Optional
C28, C29
Y1
Crystal load capacitors, 22 pF, ±5%, COG (Optional: for crystal
oscillator option)
Murata
32.768 kHz crystal (Optional: for crystal oscillator option)
Epson
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
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 VDD1/VDD2 bypass capacitor C6, C15 as close as possible to the supply (pin20/pin 21) and DBYP (pin 22).
GND
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 LMATCH, C4, F1, and F2 for a minimal
implementation. The ESD protection diodes and headphone amplifier components are system components that will
be required for proper implementation of any tuner.
Inductor LMATCH is selected to maximize the voltage gain across the FM band. LMATCH should be selected with a Q
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 RSHUNT
and, therefore, RP. Refer to “AN383: Si47xxAntenna, Schematic, and Layout Guidelines”, Appendix A, for a
complete description of RSHUNT, RP, etc.
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 CSHUNT and, therefore,
CP. If D1 and D2 must be chosen with a capacitance greater than 1 pF, they should be placed between the ferrite
beads F1 and F2 and the headphone amplifier to minimize CSHUNT. This placement will, however, reduce the
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 R1R4 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
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
Description
LMATCH
IND, 0603, SM, 270 nH, MURATA, LQW18ANR27J00D
C4
AC coupling cap, SM, 0402, X7R, 100 pF
D1, D2, D3
IC, SM, ESD DIODE, SOT23-3, California Micro Devices, CM1210-01ST
U3
IC, SM, HEADPHONE AMP, National Semiconductor, LM4910MA
R1, R2, R3, R4
RES, SM, 0603, 20 k
C7, C8
CAP, SM, 0603, 0.39UF, X7R
C5, C6
CAP, SM, 0402, C0G, 100 pF
R5, R6
RES, SM, 0603, 100 k
F1, F2
FERRITE BEAD, SM, 0603, 2.5 k, Murata, BLM18BD252SN1D
C1
CAP, SM, 0402, X7R, 0.1 µF
R7
RES, SM, 0402, 10 k
Rev. 0.3
25
AN602
4.4. Headphone Antenna Layout
To minimize inductive and capacitive coupling, inductor LMATCH and headphone jack J24 should be placed together
and as far from noise sources such as clocks and digital circuits as possible. LMATCH should be placed near the
headphone connector to keep audio currents away from the chip.
To minimize CSHUNT and CP, place ferrite beads F1 and F2 as close as possible to the headphone connector.
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 CSHUNT.
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 LMATCH to maximize signal strength across the FM band.
Select
matching inductor LMATCH with a Q of 15 or greater at 100 MHz and minimal dc resistance.
Place
inductor LMATCH and headphone connector together and as far from potential noise sources as
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
Description
WIP_ANTENNA
Whip Antenna
L1
Tuning Inductor, 0603, SM, 56 nH,
MURATA, LQW18AN56nJ00D
C5
AC coupling capacitor,
1 nF, 10%, COG
U3
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
Length
Turns
Ui
Type
Application
SL8X50MW70T
8 mm
50 mm
70
400
Mn-Zn
Desktop Radios
SL4X30MW100T
4 mm
30 mm
100
300
Ni-Zn
Portable Radios (MP3,
Cell, GPS)
SL3X30MW105T
3 mm
30 mm
105
300
Ni-Zn
SL3X25MW100T
3 mm
25 mm
110
300
Ni-An
SL5X7X100MW70T
5 x 7 mm
100 mm
70
400
Mn-Zn
Desktop Radios
The following is the vendor information for the ferrite loop antennas:
Jiaxin Electronics
Shenzhen Sales Office
email:
[email protected]
Web:
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
30
Designator
Description
Note
ANT1
Ferrite loop antenna, 180~450 µH
C1
AC coupling capacitor, 0.47 µF, 10%, Z5U/X7R
D1
ESD diode, IC, SM, SOT23-3,
California Micro Devices, CM1213-01ST
Rev. 0.3
Optional; only needed if there is any
exposed pad going to the AMI pin.
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  2 L effective
Equation 2. Expected Total Capacitance at AMI
Where:
CTotal = Total capacitance at the AMI input
Leffective = Effective inductance at the AMI input
fmax = Highest frequency in AM band
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:
2
L equivalent = N L 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
Transformer 2
Transformer 3
Vendor
Jiaxin Electronics
UMEC
UMEC
Part Number
SL9x5x4MWTF1
TG-UTB01527S
TG-UTB01526
Type
Surface Mount
Surface Mount
Through Hole
Primary Coil Turns (L1)
12T
10T
10T
Secondary Coil Turns (L2)
70T
55T
58T
Wire Gauge
ULSA / 0.07 mm x 3
n/a
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:
[email protected]
Web:
www.firstantenna.com
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
Description
LOOP_ANTENNA
Air loop antenna
T1
Transformer, 1:6 turns ratio
C1
AC coupling capacitor, 0.47 µF, 10%, Z5U/X7R
D1
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
Coupling capacitor, 0.47 µF, ±20%, Z5U/X7R
R31
Resistor, 1 k, ±5%
R41
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.
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.
Place
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
Smart.
Connected.
Energy-Friendly
Products
Quality
Support and Community
www.silabs.com/products
www.silabs.com/quality
community.silabs.com
Disclaimer
Silicon Laboratories intends to provide customers with the latest, accurate, and in-depth documentation of all peripherals and modules available for system and software implementers
using or intending to use the Silicon Laboratories products. Characterization data, available modules and peripherals, memory sizes and memory addresses refer to each specific
device, and "Typical" parameters provided can and do vary in different applications. Application examples described herein are for illustrative purposes only. Silicon Laboratories
reserves the right to make changes without further notice and limitation to product information, specifications, and descriptions herein, and does not give warranties as to the accuracy
or completeness of the included information. Silicon Laboratories shall have no liability for the consequences of use of the information supplied herein. This document does not imply
or express copyright licenses granted hereunder to design or fabricate any integrated circuits. The products must not be used within any Life Support System without the specific
written consent of Silicon Laboratories. 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 personal injury or death. Silicon Laboratories products are generally not intended for military applications. Silicon Laboratories products shall under no
circumstances be used in weapons of mass destruction including (but not limited to) nuclear, biological or chemical weapons, or missiles capable of delivering such weapons.
Trademark Information
Silicon Laboratories Inc., Silicon Laboratories, Silicon Labs, SiLabs and the Silicon Labs logo, CMEMS®, EFM, EFM32, EFR, Energy Micro, Energy Micro logo and combinations
thereof, "the world’s most energy friendly microcontrollers", Ember®, EZLink®, EZMac®, EZRadio®, EZRadioPRO®, DSPLL®, ISOmodem ®, Precision32®, ProSLIC®, SiPHY®,
USBXpress® and others are trademarks or registered trademarks of Silicon Laboratories Inc. ARM, CORTEX, Cortex-M3 and THUMB are trademarks or registered trademarks of
ARM Holdings. Keil is a registered trademark of ARM Limited. All other products or brand names mentioned herein are trademarks of their respective holders.
Silicon Laboratories Inc.
400 West Cesar Chavez
Austin, TX 78701
USA
http://www.silabs.com
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement