Si4734/35-B20

4.2. Operating Modes

The Si4734/35 operates in either an FM receive or an AM/SW/LW receive mode. In FM mode, radio signals are received on FMI (pin 2) and processed by the FM front-end circuitry. In AM/SW/LW mode, radio signals are received on AMI (pin 4) and processed by the AM front-end circuitry. In addition to the receiver mode, a clocking mode allows the Si4734/35 to be clocked from a reference clock or crystal. On the Si4735, an audio output mode is available as analog and/or digital audio output. In the analog audio output mode, pin 13 is ROUT, pin 14 is LOUT, pin 17 is GPO3. In the digital audio mode, pin 15 is DOUT, pin 16 is DFS, and pin 17 is DCLK. Concurrent analog/digital audio output mode requires pins 13, 14, 15,16, and 17. The receiver mode and the audio output mode are set by the POWER_UP command listed in Table 12. Si473x Command Summary.

4.3. FM Receiver

The Si4734/35's patented digital low-IF architecture reduces external components and eliminates the need for factory adjustments. The Si4734/35 receiver supports the worldwide FM broadcast band (76 to 108 MHz) as well as an extended FM band (64 to 76 MHz), which may include region-specific programming such as educational channels, emergency alerts, and/or television audio. An automatic gain control (AGC) circuit controls the gain of the integrated low noise amplifier (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, and digitized with high resolution analog-to-digital converters (ADCs). This advanced architecture allows the Si4734/35 to perform channel selection, FM demodulation, and stereo audio processing to achieve superior performance compared to traditional analog architectures.

4.4. AM Receiver

The highly integrated Si4734/35 supports worldwide AM band reception from 520 to 1710 kHz using a digital low- IF architecture with a minimum number of external components and no manual alignment required. This digital low-IF architecture allows for high-precision filtering, offering excellent selectivity and noise suppression. The DSP also provides 9 or 10 kHz channel selection, AM demodulation, soft mute, and additional features such as adjustable channel bandwidth settings. Similar to the FM receiver, the integrated LNA and AGC optimize sensitivity and rejection of strong interferers allowing better reception of weak stations.

The Si4734/35 provides highly accurate digital AM tuning without factory adjustments. To offer maximum flexibility, the receiver supports a wide range of ferrite loop sticks from 180–450 µH. An air loop antenna is supported by using a transformer to increase the effective inductance from the air loop. Using a 1:5 turn ratio inductor, the inductance is increased by 25 times, easily supporting all typical AM air loop antennas which generally vary between 10 and 20 µH.

4.5. SW Receiver

The Si4734/35 is the first fully integrated IC to support AM and FM, as well as short wave (SW) band reception from 2.3 to 21.85 MHz fully covering the 120 meter to 13 meter bands. The Si4734/35 offers extensive shortwave features such as continuous digital tuning with minimal discrete components and no factory adjustments. Other SW features include adjustable channel step sizes in 1 kHz increments, adjustable channel bandwidth settings, advanced seek algorithm, and soft mute.

The Si4734/35 uses the FM antenna to capture short wave signals. These signals are then fed directly into the AMI pin in a wide band configuration. See “AN382: Si4734/35 Designer’s Guide” for more details.

4.6. LW Receiver

The Si4734/35 supports the long wave (LW) band from 153 to 279 kHz. The highly integrated Si4734/35 offers continuous digital tuning with minimal discrete components and no factory adjustments. The Si4734/35 also offers adjustable channel step sizes in 1 kHz increments, adjustable channel bandwidth settings, advanced seek algorithm, and soft mute.

The Si4734/35 uses a separate ferrite bar antenna to capture long wave signals.

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Silicon Laboratories SI4734/35-B20 manual Operating Modes, FM Receiver, AM Receiver, SW Receiver, LW Receiver
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SI4734/35-B20 specifications

Silicon Laboratories SI4734/35-B20 is an advanced, highly integrated broadcast radio receiver designed for various consumer applications. Hailed for its compactness and versatility, the SI4734/35-B20 offers extensive features that enable radio reception across multiple frequency bands, including AM, FM, and shortwave. It caters to the needs of manufacturers looking to incorporate reliable radio capabilities into their devices, ensuring quality sound and performance without the cumbersome designs typically associated with traditional radio receivers.

At the heart of the SI4734/35-B20 are performance-optimized technologies. One standout feature is the device's ability to support digital and analog processing simultaneously, utilizing Silicon Labs’ proprietary digital signal processing (DSP) technology. This architecture not only enhances signal clarity but also helps in mitigating noise, enabling users to experience a superior audio quality across varied environments.

Another notable characteristic of the SI4734/35-B20 is its low power consumption, making it ideal for battery-operated devices. The receiver employs sophisticated power management techniques that allow it to operate efficiently, prolonging battery life while maintaining optimal performance. In this context, the “sleep” mode and fast wake-up times contribute to significant energy savings, affirming its suitability for portable applications.

The SI4734/35-B20 is designed with a robust set of features for ease of integration into various systems. The device supports multiple programmable interfaces, including I2C, providing flexibility in communication with microcontrollers and facilitating straightforward integration into existing designs. Because of its programmable architecture, developers can customize the receiver’s capabilities according to the specific needs of their applications.

Additional features include automatic frequency control (AFC) for stability in tuning, allowing seamless transitions while listening to programs. The built-in AGC (automatic gain control) optimizes the receiver's sensitivity to ensure clear reception even in weak signal conditions.

The SI4734/35-B20 also possesses a wide frequency range, accommodating both standard and niche applications. Its compact form factor and surface-mount technology (SMT) footprint further enhance its appeal to developers seeking to maximize board space in their designs.

In conclusion, the Silicon Laboratories SI4734/35-B20 is a significant advancement in radio receiver technology, combining advanced DSP, low power consumption, and ease of integration. These attributes make it a preferred choice for engineers and manufacturers looking to deliver high-quality audio experiences across a range of consumer electronics, from radios to multifunctional smart devices.
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