Silicon Labs recently introduced the Si484x AM/FM/SW receiver family to meet the needs of the ATDD radio market. The Si484x family is based on a digital low-IF architecture that provides a full radio from a very simple antenna interface to L/R analog audio out. The Si484x ICs feature a built-in ADC that can directly interpret the analog tuning of the wheel to frequency changes while providing I2C-compatible 2-wire control to a combined MCU and LED/LCD driver.
Unlike a traditional analog IC that cannot output the tuned frequency, the Si484x outputs the actual tuned frequency and supports indicators for valid stations and mono/stereo signals to display on the LCD/LED. The Si484x provides digital volume control, soft mute and bass/treble audio enhancements. Additionally, it offers audio conditioning for all signal environments, removing pops, clicks and loud static in variable signal conditions.
Figure 4. Si484x multi-band radio IC architecture.
New ATDD radios using solutions, as shown in Figure 4, bring several important benefits of modern digital radios to this traditional analog market. Let’s examine each of these benefits.
Reduced BOM and labor costs: Compared to traditional analog radio ICs, the integrated Si484x solution reduces BOM cost by more than 70 percent. In contrast, traditional solutions require several steps of manual tuning and testing, which increases labor cost and manufacturing time. The Si484x requires no manual tuning and needs only a single test of RF to analog. Compared to click-wheel radio solutions, the Si484x eliminates the need for the encoder while providing the advanced features comparable to click-wheel radio designs.
Superior RF performance: The selectivity parameter of a radio determines how well it can detect a target radio station in the presence of many other radio stations, a common scenario in crowded cities. Traditional analog radios use a wide channel filter with 800 kHz to 1 MHz bandwidth for FM band, which means radio stations within this bandwidth will interfere with one another and degrade the sound quality of the desired station. The Si484x radio ICs have a digital selectivity filter with narrow bandwidth that enables reception of the targeted station even in the presence of 50 dB stronger interfering radio stations as close as 200 kHz away. Figure 5 presents the Si484x family’s selectivity compared to traditional solutions. The selectivity value shown in Figure 5 is the minimum amount of delta required for blockers to interfere with the reception of the desired signal.
Figure 5. Si484x selectivity compared to traditional analog ICs.
Accurate tuned frequency display: Traditional ATDD solutions use frequency counter ICs to approximate the tuned frequency of legacy analog ICs. This can frequently lead to the actual tuned frequency being significantly different than the displayed frequency, resulting in a poor user experience. The Si484x tuning experience is precise.
Easy to design and build: Digital-based solutions are more highly integrated than traditional analog solutions, and therefore generally easier to design onto the printed circuit board. For example, the Si484x family’s digital architecture supports a small front-end matching network, voltage supply isolation and functional configuration. The architecture is implemented on a single-layer board, resulting in a simple system BOM. There are no manually-tuned parts, allowing manufacturers to eliminate labor involved with manual placement, testing and tweaking from their assembly lines.
Global competition in the radio market challenges radio system designers to consider all factors in their wheel-tuned, digital-display radio designs including RF performance, BOM cost and manufacturing flow. By using highly integrated multi-band radio receiver ICs, radio manufacturers can significantly reduce BOM and manufacturing costs while designing radio products with differentiated features that will stand out in today’s radio market.
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About the Author
Natalian Zhai, Broadcast Audio Product Marketing Manager, Silicon Labs
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Natalian Zhai, Sr. product marketing manager for Silicon Lab’s Broadcast Audio products, manages the multi-band radio product line for the company’s consumer electronics (CE) business. Ms. Zhai joined Silicon Labs in 2003, initially serving as a business manager and senior technical sales engineer in the company’s sales department, responsible for product lines in the Asia market. Later she moved into marketing and managed the Si470x FM receiver product line for the handset and portable media player (PMP) business. Prior to her work at Silicon Labs, she studied at Rice University (Houston, Texas) where she obtained master’s degrees in Electrical Engineering and Business Administration. She also holds a Bachelor of Science in Electrical Engineering from the Beijing Institute of Technology.