SI4703-B17-GMR Silicon Laboratories Inc, SI4703-B17-GMR Datasheet - Page 15

• Manufacturer Part Number: SI4703-B17-GMR
• Description: IC TUNER FM RADIO RDS/RBDS 20QFN
• Manufacturer: Silicon Laboratories Inc

Specifications of SI4703-B17-GMR

• Frequency: 76MHz ~ 108MHz
• Sensitivity: *
• Data Rate - Maximum: *
• Modulation Or Protocol: *
• Applications: *
• Current - Receiving: *
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Features: *
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: *
• Package / Case: 20-VQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Size: -

The Si4703's integrated stereo decoder 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
respectively. The Si4703 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
to maintain optimum sound fidelity under varying
reception conditions. The signal level range over which
the stereo to mono blending occurs can be adjusted by
setting the BLNDADJ[1:0] register. Stereo/mono status
can be monitored with the ST register bit and mono
operation can be forced with the MONO register bit.
Pre-emphasis and de-emphasis is a technique used by
FM broadcasters to improve the signal-to-noise ratio of
FM receivers by reducing the effects of high frequency
interference and noise. When the FM signal is
transmitted, a pre-emphasis filter is applied to
accentuate the high audio frequencies. All FM receivers
incorporate a de-emphasis filter which attenuates high
frequencies to restore a flat frequency response. Two
time constants, 50 or 75 µs, are used in various regions.
The de-emphasis time constant is programmable with
the DE bit.
High-fidelity stereo digital-to-analog converters (DACs)
drive analog audio signals onto the LOUT and ROUT
pins. The audio output may be muted with the DMUTE
bit. Volume can be adjusted digitally with the
VOLUME[3:0] bits. The volume dynamic range can be
set to either –28 dBFS (default) or –58 dBFS by setting
VOLEXT=1.
The soft mute feature is available to attenuate the audio
outputs and minimize audible noise in weak signal
conditions. The soft mute attack and decay rate can be
adjusted with the SMUTER[1:0] bits where 00 is the
fastest setting. The soft mute attenuation level can be
0
subtracting
Mono Audio
Left + Right
Figure 8. MPX Signal Spectrum
15
Stereo
Pilot
the
19
Frequency (kHz)
23
(L+R)
Stereo Audio
Left - Right
and
38
(L-R)
53
RBDS
Confidential Rev. 1.0
RDS/
signals,
57
adjusted with the SMUTEA[1:0] bits where 00 is the
most attenuated. The soft mute disable (DSMUTE) bit
may be set high to disable this feature.
4.6. Tuning
The Si4703 uses Silicon Laboratories’ patented and
proven frequency synthesizer technology including a
completely integrated VCO. The frequency synthesizer
generates the quadrature local oscillator signal used to
downconvert the RF input to a low intermediate
frequency. The VCO frequency is locked to the
reference clock and adjusted with an automatic
frequency control (AFC) servo loop during reception.
The tuning frequency is defined as:
Channel spacing of 50, 100 or 200 kHz is selected with
bits SPACE[1:0]. The channel is selected with bits
CHAN[9:0]. Band selection for Japan, Japan wideband,
or Europe/U.S./Asia is set with BAND[1:0]. The tuning
operation begins by setting the TUNE bit. After tuning
completes, the seek/tune complete (STC) bit will be set
and the RSSI level is available by reading bits
RSSI[7:0]. The TUNE bit must be set low after the STC
bit is set high in order to complete the tune operation
and clear the STC bit.
Seek tuning searches up or down for a channel with an
RSSI greater than or equal to the seek threshold set
with the SEEKTH[7:0] bits. In addition, optional SNR
and/or impulse noise detector criteria may be used to
qualify valid stations. The SKSNR[3:0] bits set the SNR
threshold required. The SKCNT[3:0] bits set the impulse
noise threshold. Using the extra seek qualifiers can
reduce false stops and, in combination with lowering the
RSSI seek threshold, increase the number of found
stations. The SNR and impulse noise detectors are
disabled by default for backwards compatibility.
Two seek modes are available. When the seek mode
(SKMODE) bit is low and a seek is initiated, the device
seeks through the band, wraps from one band edge to
the other, and continues seeking. If the seek operation
is unable to find a valid channel, the seek failure/band
limit (SF/BL) bit is set high and the device returns to the
channel selected before the seek operation began.
When the SKMODE bit is high and a seek is initiated,
the device seeks through the band until the band limit is
reached and the SF/BL bit is set high. A seek operation
is initiated by setting the SEEK and SEEKUP bits. After
the seek operation completes, the STC bit is set, and
the RSSI level and tuned channel are available by
reading bits RSSI[7:0] and bits READCHAN[9:0]. During
a seek operation READCHAN[9:0] is also updated and
may be read to determine and report seek progress.
Freq (MHz)
=
Spacing (kHz) Channel

Si4703-B17
+
Bottom of Band (MHz)
15