Si4704/05-C40
18 Rev. 1.0
4. Functional Description
4.1. Overview
Figure 9. Functional Block Diagram
The Si4704/05 device leverages Silicon Laboratories’
highly successful and proven Si4700/01/02/03 FM
receiver, and offers unmatched integration and
performance. The Si4704/05 offers additional features,
such as EN55020 compliance, embedded antenna
support, and a digital audio interface. The Si4704/05 is
layout compatible with Silicon Laboratories’ Si4710/11
FM Transmitter, Si4720/21 FM Transceiver, and
Si4730/31 AM/FM Receiver. The Si4704/05 is the first
FM radio receiver integrated circuit to support a short
PCB trace or wire antenna, which can be integrated into
the enclosure or PCB.
The Si4704/05’s digital integration reduces the required
external components of traditional offerings, resulting in
a solution requiring only an external inductor and
bypass capacitor, and occupying board space of
approximately 15 mm
2
. Other advantages of the
Si4704/05 include highly reliable device manufacturing,
excellent quality, and ease of use to design-in and
program.
The Si4704/05 includes line outputs from the on-chip
digital-to-analog converters (DAC), digital audio mixers,
a programmable reference clock input, and a
configurable digital audio interface with the Si4705. The
chip supports an I
2
C-compliant 2-wire interface, an
Si4700/01/02/03 backwards compatible 3-wire control
interface, and an SPI control interface.
The Si4704/05 performs much of the FM demodulation
digitally to achieve high fidelity, optimal performance
versus power consumption, and flexibility of design. The
on-board DSP provides unmatched pilot rejection,
selectivity, and optimum sound quality. The Si4704/05
offers both the manufacturer and the end-user
unmatched programmability and flexibility in the
listening experience.
The Si4705 incorporates on-board processing capability
for the European Radio Data System (RDS) and the US
Radio Broadcast Data System (RBDS) including all the
symbol encoding/decoding, block synchronization, error
detection, and error correction functions. 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.
The Si4704/05 has two separate RF inputs. FMI is the
input for use with a traditional FM antenna. The LPI
input is for use with a short PCB trace or wire antenna
that may be integrated into the system enclosure. There
is a clocking mode to choose to clock the Si4704/05
from a reference clock or crystal. On the Si4705, there
is an audio output mode to choose between an analog
and/or digital audio output.
ADC
ADC
Si4704/05
DSP
DAC
DAC
ROUT
LOUT
AFC
DIGITAL INTERFACE
(Si4705)
GPO
RFGND
LNA
FMI
AGC
PGA
RCLK
REG
VDD
2.7–5.5 V
FM Antenna
XTAL
OSC
LPI
32.768 kHz
0/90
DOUT
DCLK
DFS
VIO
1.85-3.6 V
SCLK
SDIO
CONTROL
INTERFACE
SEN
RSSI
RST
RDS
(Si4705)
