SI4720-B20-GMR Datasheet, PDF (24/48 Pages) Silicon Laboratories – BROADCAST FM RADIO TRANSCEIVER FOR PORTABLE APPLICATIONS

Si4720/21-B20
5. Functional Description
5.1. Overview
Tx/Rx Ant
TXO
L1
120 nH
Si4720
LIN
RIN
Rx Ant*
FMI
LNA
ADC
DAC
ROUT
PGA
DSP
RFGND
AGC
ADC
DAC
LOUT
2.7–5.5 V VDD
C1 GND
22 uF
LDO
AFC
GPO
CONTROL
INTERFACE
*Note: Dedicated Rx antenna is optional
Figure 14. Functional Block Diagram
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 Laboratories’
highly successful and proven FM technology and offers
unmatched integration and performance. FM receiver
and transmit functionality may be added to any portable
device by using this 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 is the first FM radio transceiver
integrated circuit to support a small loop antenna, which
can be integrated into the enclosure or PCB of a
portable device. This feature enables applications that
also include Bluetooth functionality to perform FM radio
reception without cables. For portable navigation
devices, the Si4720’s antenna architecture permits
integration of the traffic messaging antenna into the
enclosure of the portable device, and eliminates the
need for external antenna cables.
The Si4720'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 mm². 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.
The Si4720/21’s integrated receive power scan function
shares the same antenna as the transmitter allowing for
a compact printed circuit board design. The device
operates in half duplex mode, meaning the transmitter
and receiver do not operate at the same time.
The Si4720/21 performs FM modulation in the digital
domain to achieve high fidelity, optimal performance
versus power consumption, and flexibility of design. The
onboard DSP provides modulation adjustment and
audio dynamic range control for optimum sound quality.
The Si4721 supports the European Radio Data System
(RDS) and the US Radio Broadcast Data System
(RBDS) including all the symbol encoding, block
synchronization, and error correction functions. Using
this feature, the Si4721 enables data such as artist
name and song title to be transmitted to an RDS/RBDS
receiver.
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Rev. 1.0