SI4734-C40-GM Silicon Laboratories Inc, SI4734-C40-GM Datasheet - Page 23

• Manufacturer Part Number: SI4734-C40-GM
• Description: IC RX AM/FM/SW/LW RADIO 20UQFN
• Manufacturer: Silicon Laboratories Inc

Specifications of SI4734-C40-GM

• Frequency: 153kHz ~ 279kHz, 520kHz ~ 1.71MHz, 2.3MHz ~ 26.1MHz, 64MHz ~ 108MHz
• Modulation Or Protocol: AM, FM, SW-LW
• Applications: General Purpose
• Current - Receiving: 19.9mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Features: RSSI Equipped
• Voltage - Supply: 2.7 V ~ 5.5 V
• Operating Temperature: -20°C ~ 85°C
• Package / Case: 20-UQFN, 20-µQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Sensitivity: -
• Memory Size: -
• Data Rate - Maximum: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

5.8. 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 13 below.
(OMODE = 1000)
(OMODE = 1100)
(OMODE = 0110)
(OMODE = 0000)
(OFALL = 0)
Left-Justified
0
(OFALL = 1)
(OFALL = 0)
(OFALL = 1)
(OFALL = 0)
I
2
Mono Audio
S
Left + Right
Figure 13. MPX Signal Spectrum
(MSB at 2
(MSB at 1
INVERTED
INVERTED
DOUT
DCLK
DCLK
DOUT
DFS
DCLK
DCLK
nd
st
DFS
rising edge)
rising edge)
15
Stereo
Pilot
DOUT
DOUT
DCLK
19
DFS
Frequency (kHz)
23
1 DCLK
MSB
1
1 DCLK
MSB
1
MSB
Figure 11. Left-Justified Digital Audio Format
Stereo Audio
1
2
Left - Right
2
MSB
38
Figure 12. DSP Digital Audio Format
2
1
Figure 10. I
3
3
LEFT CHANNEL
3
2
LEFT CHANNEL
LEFT CHANNEL
3
n-2
53
n-2
LEFT CHANNEL
2
RBDS
RDS/
S Digital Audio Format
n-2
57
n-1
Rev. 1.0
n-1
n-1
n-2
LSB
LSB
5.8.1. Stereo Decoder
The
automatically decodes the MPX signal using DSP
techniques. 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. Output
left and right channels are obtained by adding and
subtracting the (L+R) and (L–R) signals respectively.
The Si4735 uses frequency information from the 19 kHz
stereo pilot to recover the 57 kHz RDS/RBDS signal.
5.8.2. Stereo-Mono Blending
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. Stereo/mono status can be
monitored with the FM_RSQ_STATUS command. Mono
operation
FM_BLEND_MONO_THRESHOLD property.
n
n
LSB
n-1
n
Si4734/35's
MSB
LSB
1
n
MSB
1
MSB
1 DCLK
2
1
MSB
can
1
2
3
2
2
RIGHT CHANNEL
3
Si4734/35-C40
integrated
be
3
3
RIGHT CHANNEL
RIGHT CHANNEL
RIGHT CHANNEL
n-2
forced
n-2
n-1
n-2
n-2
stereo
n-1
LSB
n-1
n-1
n
LSB
with
n
LSB
LSB
n
n
decoder
the
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