SI4709-B-GM Silicon Laboratories Inc, SI4709-B-GM Datasheet - Page 14

• Manufacturer Part Number: SI4709-B-GM
• Description: IC FM RADIO TUNER 20-QFN
• Manufacturer: Silicon Laboratories Inc
• Series: -r

Specifications of SI4709-B-GM

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Si4708/09-B
The Si4708/09’s patented digital low-IF architecture
reduces external components and eliminates the need
for factory adjustments. The receive (RX) section
integrates a low noise amplifier (LNA) supporting the
worldwide FM broadcast band (76 to 108 MHz). An
automatic gain control (AGC) circuit controls the gain of
the LNA to optimize sensitivity and rejection of strong
interferers.
An image-reject mixer downconverts the RF signal to
low-IF. The quadrature mixer output is amplified,
filtered,
analog-to-digital converters (ADCs). This advanced
architecture achieves superior performance by using
digital signal processing (DSP) to perform channel
selection,
processing
architectures.
4.3. General Purpose Output
The GPO pin can serve multiple functions. After
powerup of the device, the GPO pin can be used as a
general purpose input/output, and can be used as an
interrupt request pin for the seek/tune or RDS ready
functions. See register 04h, bits [3:2] in Section “6.
Register Descriptions” for information on GPO control. It
is recommended that the GPO pin not be used as an
interrupt request output until the powerup time has
completed (see Section “4.9. Reset, Powerup, and
Powerdown”). The GPO pin is powered from the V
supply;
functionality is available regardless of the state of the V
and V
4.4. RDS/RBDS Processor and
The Si4709 implements an RDS/RBDS processor for
symbol
detection, and error correction. RDS functionality is
enabled by setting the RDS bit. The device offers two
RDS modes, a standard mode and a verbose mode.
The primary difference is increased visibility to RDS
block-error levels and synchronization status with
verbose mode.
Setting the RDS mode (RDSM) bit low places the
device in standard RDS mode (default). The device will
set the RDS ready (RDSR) bit for a minimum of 40 ms
when a valid RDS group has been received. Setting the
RDS interrupt enable (RDSIEN) bit and GPO[1:0] = 01
will configure GPO to pulse low for a minimum of 5 ms
when a valid RDS group has been received. If an invalid
group is received, RDSR will not be set and GPO will
not pulse low. In standard mode RDS synchronization
(RDSS) and block error rate A, B, C and D (BLERA,
14
D
Functionality
supplies, or the ENABLE and DISABLE bits.
therefore,
decoding,
and
FM
compared
demodulation,
digitized
general
block
to
with
synchronization,
purpose
and
traditional
high
stereo
input/output
resolution
Confidential Rev. 1.4
analog
audio
error
IO
A
BLERB, BLERC, and BLERD) are unused and will read
0. This mode is backward compatible with earlier
firmware revisions.
Setting the RDS mode bit high places the device in RDS
verbose mode. The device sets RDSS high when
synchronized and low when synchronization is lost. If
the device is synchronized, RDS ready (RDSR) will be
set for a minimum of 40 ms when a RDS group has
been received. Setting the RDS interrupt enable
(RDSIEN) bit and GPO[1:0] = 01 will configure GPO to
pulse low for a minimum of 5 ms if the device is
synchronized and an RDS group has been received.
BLERA,
block-error levels for the RDS group. The number of bit
errors in each block within the group is encoded as
follows: 00 = no errors, 01 = one to two errors, 10 =
three to five errors, 11 = six or more errors. Six or more
errors in a block indicate the block is uncorrectable and
should not be used.
4.5. Stereo Audio Processing
The output of the FM demodulator is a stereo
multiplexed (MPX) signal. The MPX standard was
developed in 1961 and is used worldwide. Today's MPX
signal format consists of left + right (L+R) audio, left –
right (L–R) audio, a 19 kHz pilot tone, and RDS/RBDS
data as shown in Figure 7.
The
automatically decodes the MPX signal. The 0 to 15 kHz
(L+R) signal is the mono output of the FM tuner. Stereo
is generated from the (L+R), (L-R), and a 19 kHz pilot
tone. The pilot tone is used as a reference to recover
the (L-R) signal. Separate left and right channels are
obtained by adding and subtracting the (L+R) and (L-R)
signals, respectively. The Si4709 uses frequency
information from the 19 kHz stereo pilot to recover the
57 kHz RDS/RBDS signal.
Adaptive noise suppression is employed to gradually
combine the stereo left and right audio channels to a
mono (L+R) audio signal as the signal quality degrades
0
Si4708/09's
Mono Audio
Left + Right
Figure 7. MPX Signal Spectrum
BLERB,
15
Stereo
Pilot
19
Frequency (kHz)
BLERC
23
integrated
Stereo Audio
Left - Right
and
38
stereo
BLERD
53
RBDS
RDS/
decoder
provide
57