Si4720/21
Broadcast FM Radio Transceiver for Portable Applications
Description
The Si4720/21 is the first single chip FM radio transceiver.
The proven and patented digital architecture of the Si4720/
21 combines the functionality of the Si470x FM radio
receiver with the Si471x FM transmitter, offering full FM
receive and transmit capabilities in a single, ultra-small
3x3x0.55 mm QFN package. The device leverages Silicon
Lab's highly successful and proven FM technology, and
offers unmatched integration and performance allowing FM
receive and transmit to be added to any portable device by
using a single chip. As with the Si470x and Si471x
products, the Si4720/21 offers industry leading size,
performance, low power consumption, and ease of use.
The Si4720/21's digital integration reduces the required
external components of traditional offerings, resulting in a
solution requiring only an external inductor and bypass
capacitor, and a PCB space of approximately 15 mm
2
. The
Si4720/21 is layout compatible with Silicon Laboratories'
Si470x FM radio receivers, Si473x AM/FM radio receivers,
and the Si471x FM radio transmitter solutions, allowing a
single PCB layout to accommodate a variety of music
features. High yield manufacturability, unmatched
performance,
easy
design-in,
and
software
programmability are key advantages of the Si4720/21.
The Si4721 is the industry's first single-chip integrated FM
radio transceiver including both receive and transmit
support for the European Radio Data System (RDS) and
the U.S. Radio Broadcast Data System (RBDS) standards.
RDS allows digital information sent from the broadcaster to
be displayed, such as station ID, song name and music
category. In Europe, alternate frequency (AF) information is
also provided to automatically change stations in areas
where broadcasters use multiple frequencies. In transmit
mode, digital information such as artist name, song title,
music category, and branded messaging can be
transmitted and displayed on any RDS/RBDS receiver.
Users are responsible for adjusting their system's radiated
power levels to comply with local regulations on RF
transmission (FCC, ETSI, ARIB, etc.).
Features
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Integrated FM antenna support
Excellent real-world performance
Only two external components required
Worldwide FM band support (76 to 108 MHz)
RDS/RBDS processor (Si4721)
Frequency synthesizer with integrated VCO
Adjustable seek parameters
Adjustable mono/stereo blend
Adjustable soft mute
Programmable transmit output voltage control
Audio dynamic range control
Advanced modulation control
Analog/digital audio interface
Programmable reference clock input
Programmable pre/de-emphasis (50/75 µs)
2-wire and 3-wire control interface
Integrated LDO regulator
2.7 to 5.5 V supply voltage
3x3x0.55 mm 20-pin Pb-free QFN package
Cellular handsets/hands free
MP3 players
Portable media players
GPS/navigation devices
Satellite digital audio radios
Personal computers
Applications
Si4720/21
Tx/Rx Ant
TXO
L1
120 nH
LIN/DFS
RIN/DOUT
ADC
PGA
MUX
LNA
AGC
DSP
ADC
DAC
LOUT/DFS
DAC
ROUT/DIN
Headphone
Rx Ant*
FMI
RFGND
2.7–5.5 V
VDD
C1
22 uF
GND
LDO
AFC
GPO
CONTROL
INTERFACE
GPO3/DCLK
GPO2/INT
SDIO
RCLK
SCLK
SEN
*Note: Dedicated Rx antenna is optional
FM Transceiver
Copyright © 2008 by Silicon Laboratories
GPO1
RST
VIO
3.26.08
Si4720/21
Broadcast FM Radio Transceiver for Portable Applications
Selected Electrical Specifications
Parameter
Frequency Range
Sensitivity Headphone Matching
Sensitivity 50
Matching
Input IP3
Adjacent Channel Selectivity
Alternate Channel Selectivity
RX Audio Output Voltage
RX Audio Mono S/N
RX Audio THD
Programmable Transmit Output
Voltage, TXO
Transmit Voltage Accuracy
Transmit Channel Edge Power
Transmit Adjacent Channel Power
Pre/de-emphasis Time Constant
TX Audio SNR
TX Audio THD
TX Audio Stereo Separation
TX Sub Carrier Rejection Ratio
TX Audio Input Signal Level (0 dB)
Supply Voltage
Interface Supply Voltage
RX Supply Current
TX Supply Current
Symbol
f
RF
Test Condition
(S+N)/N = 26 dB
(S+N)/N = 26 dB
|f
2
– f
1
| > 1 MHz; f
0
= 2 x f
1
– f
2
AGC disabled
±200 kHz
±400 kHz
Min
76
—
—
100
35
60
72
55
—
—
–2.5
—
—
70
45
—
—
30
40
—
2.7
1.5
—
—
Typ
—
2.2
1.1
105
50
70
80
63
0.1
118
—
—
–30
75
50
63
0.1
35
50
—
—
—
19.2
18.8
Max
108
3.5
—
—
—
—
90
—
0.5
—
2.5
–20
–26
80
54
—
—
—
—
0.636
5.5
3.6
22
22.8
Unit
MHz
µV EMF
µV EMF
dBµV EMF
dB
dB
mVrms
dB
%
dBµV
dB
dBC
dBC
us
us
dB
%
dB
dB
V
pk
V
V
mA
mA
V
RF
= 102–118 dBµV
TX_PREMPHASIS = 75 µs
TX_PREMPHASIS = 50 µs
SCR
V
AI
V
DD
V
IO
I
RX
I
TX
V
IO
= 1.8 V
FM TX from Line Input
Pin Assignments
GPO3/DCLK
Package Information
NC
1
20 19 18 17 16
15 RIN/DIO
FMI 2
RFGND 3
TXO 4
RST 5
6
SEN
7
SCLK
8
SDIO
9
RCLK
GND
PAD
10 11 VDD
VIO
Symbol
A
A1
b
c
D
D2
e
E
E2
Min
0.50
0.00
0.18
0.27
1.60
Millimeters
Nom
0.55
0.02
0.25
0.32
3.00 BSC
1.70
0.50 BSC
3.00 BSC
1.70
Symbol
Max
0.60
0.05
0.30
0.37
1.80
f
L
L1
aaa
bbb
ccc
ddd
eee
Millimeters
Min
Nom
2.53 BSC
0.35
0.40
0.00
—
—
—
—
—
—
—
—
—
—
—
LIN/DFS
14 LOUT/DFS
13 ROUTDIO
12 GND
GPO1
GPO2
NC
Max
0.45
0.10
0.10
0.10
0.08
0.10
0.10
1.60
1.80
FM Transceiver
Copyright © 2008 by Silicon Laboratories
3.26.08
Silicon Laboratories and Silicon Labs are trademarks of Silicon Laboratories Inc.
Other products or brandnames mentioned herein are trademarks or registered trademarks of their respective holders
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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
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