This article refers to the address: http://
With the advent of digital recording and transmission, the idea of ​​combining digital sources directly with digital processing to provide an end-to-end digital audio system seems to be coming soon. End-to-end digital audio ensures that digital audio sources—whether CD, DVD, or HDTV—restore the high resolution of their recordings or transmissions “as isâ€. In addition, it makes audio and video a feature of many consumer products, not just a single-function product. The most notable examples are audio players on cell phones, video hard drives in TV set-top boxes, and even audio/video playback capabilities on computers. As audio/video system integration increases and costs decrease, this is just the beginning of a digital life explosion.
Consumers have embraced the digital lifestyle with enthusiasm. Not too long ago, TiVo and MP3 players and HDTVs were technically novel. Nowadays, digital video recorders (DVRs) and iPods and flat-panel TVs are a cool product that is forming today's popular culture. Consumers are beginning to pay attention to the convenience and coolness of digital life, even if there are some compromises in terms of traditional product quality standards, such as audio fidelity. Of course, consumers still value fidelity, they still prefer products with better sound effects, but the lower audio fidelity does not prevent them from accepting this digital lifestyle. Technology must bridge this gap.
Digitalization of system architecture
The system architecture of consumer products is increasingly digitized, driven by the explosive demand for digital connectivity. With advances in processor technology for digital signal processing and complex functional algorithms such as MPEG decoding and video scaling, the implementation of new product categories, such as digital HDTV (Figure 1), has become a reality. Filtering and demodulation functions that have been implemented using analog technology in the past are now implemented digitally with lower cost and power consumption and higher performance. As shown in Figure 2, the areas covered by numbers in the system architecture are constantly expanding, will be closer to the boundaries of the real world, and cover more and more system functions.
Digital system-on-chip (SoC) integration has become a key technology for the digitization of system architectures and has driven a dramatic increase in price/performance. According to Moore's Law, the process size has dropped from 0.25 microns to 0.18 microns, to 0.13 microns, and is now below 100 nm. Process innovations in memory and mixed-signal circuits, as well as advances in DSP/RISC processor architectures, enable more features to be integrated at lower cost and smaller silicon. The creation of new companies like Broadcom and Marve is taking advantage of this powerful industry trend, enabling very complex system architectures to be implemented on a single SoC.
Figure 1: Current digital flat panel TV system architecture
Figure 2: Future digital flat panel TV system architecture
System interface chip Tornado
Although digital SoC integration has had a huge impact on consumer electronics, the fact remains that we are still living in a simulated world, and these large-scale digital SoCs must interface with this analog world. This system interface includes three main functions that utilize mixed signal and power simulation techniques: system support, communication interfaces, and consumer interfaces.
System support functions are primarily the interface between external power supplies and increasingly complex system power management. The communication interface connects the digital SoC to a data communication network such as Ethernet, Wi-Fi, Bluetooth, USB, and cellular networks. The consumer interface enables the interface between the user and the digital world, including display drivers, microphone inputs, audio/video line in/out, and audio amplifier output to the speakers.
Although the SoC cost-effective learning curve (Figure 3) has been very steep over the past decade, the system interface functionality has only limited improvement. Until recently, this remained the norm as digital SoC capabilities represented major system costs and opportunities for improvement. However, this situation has changed. The cost of system interface functions accounts for a large proportion of IC costs, creating a golden opportunity for investment and accelerating the cost-effective learning curve.
Figure 3: SoC SIC price-performance learning curve and system integration architecture.
Today, the convergence of three industry factors has created a “perfect storm†around the system interface function, similar to what the SoC has experienced in the past. First, the market is driven by consumer demand for digital lifestyles, and technological advances in the generation, storage, transmission, and processing of digital content have also contributed to market growth. Second, key semiconductor process technologies such as high voltage (HV) CMOS have become practical, which has also driven the economies of scale that must be required to integrate system interface functions at low cost (requiring power supply analog circuits). Third, there are innovative architecture technologies that can be used for power simulation functions such as power management and audio amplification. With the trend of SoC integration, these three forces have strengthened each other, forming a strong support for system interface chip (SIC) integration.
Audio is the key to consumer electronics
Portability and usability are key to the success of today's consumer-recommended products (as evidenced by the iPod), and the key technologies to achieve these product features are portability power management SICs and usability audio SICs. Audio is a key part of current consumer electronics. In fact, it's hard to imagine which product—from flat-panel TVs to cell phones, laptops, personal media players to video recorders and even digital cameras—does not or will not have audio capabilities in one way or another. Thus, audio is a natural key driver of SIC integration.
It's not just the audio, audio quality—or, more accurately—the fidelity of audio—is important to the quality that the end product is perceived by consumers. People's treatment of the sound experience is both conscious and subconscious to form a feeling and judge. The audio is always in the front and in the middle, and you need to be able to hear the sound of the button press, the sound of the knob rotation, or the clarity, warmth and detail of the soundtrack.
Even when evaluating the image quality of a high-definition flat-panel TV, consumers will have a higher evaluation of the image if it is accompanied by a higher-fidelity sound. System design engineers need to pay special attention to the fidelity of the audio they design in consumer electronics, and choose to meet system power, interface compatibility, form factor, consistency, and cost requirements without compromising audio fidelity. Technology.
Digital Amplifier - the key to audio SIC
Designing a true high-fidelity audio device is tricky. A number of factors that can be understood and difficult to understand affect the audio fidelity experienced. For good audio quality, although testable metrics such as total harmonic distortion (THD) and signal-to-noise ratio (SNR) are necessary, they usually do not give the overall picture. Taking an audio amplifier as an example for a high-definition TV, both amplifiers have a THD of 0.1 to 0.2% and a SNR of 105 dB, but still have a very different sound experience, depending on the characteristics of the distortion and noise. It also depends on how much the amplifier can realistically reproduce very small audio signals. For example, a signal amplifier capable of reproducing 100dB of full-scale signals has a softer, clearer, crisper sound experience than an amplifier with only 85dBFS. Therefore, despite the importance of test specifications, the art of audio amplifier design depends on the balance of multiple design factors and the very detailed subjective judgment of the “Golden Ear†expert.
Audio fidelity ultimately depends on the horn and power amplifier, which is the last function of the audio signal link, where the electronic signal is converted into an audible sound signal. The transition between different fields is always tricky, and it is also disadvantageous here. In current system architectures using digital SoCs, an amplifier is needed to convert the bits of digital audio into a power analog signal that can drive a low-impedance speaker voice coil to produce sound waves that our ears can hear. In fact, it is difficult, but necessary, to implement this function at low cost—in accordance with the overall system requirements and without sacrificing the fidelity of the sound.
Although the traditional combination of A/B analog amplifiers and audio digital-to-analog converters (DACs) was originally used to accomplish this task, this solution does not meet the power and integration capabilities of today's digital system architecture requirements. Class D amplifiers were initially driven by the thermal sensitivity of flat-panel TVs and are now being adopted by many digital audio systems for their superior efficiency, with an efficiency of 90% and only 50% for A/B amplifiers. The key challenge of current audio-based consumer electronics products is the development of high-fidelity amplifier technology using Class D power stages and digital signal interfaces.
Clearly, digital audio amplifier technology is the key to SIC integration in audio systems. Audio is widely available in current consumer electronics and is the most important for feeling product quality. The digital lifestyle has driven new product requirements with unique digital audio amplifier attributes, and the digitalization of the system architecture has pushed the digital interface closer to real-life boundaries. The semiconductor economy is driving SIC integration to include all of its features; in this quest, integrating digital audio amplifiers is the most critical challenge. It can be said that in consumer products, the integration of digital amplifier technology with analog SIC is absolutely necessary, just as video and image processing technology is absolutely necessary compared to digital SoC.
HDTV digital amplifier considerations
In considering digital consumer electronics design, such as high-definition flat-panel TVs, three digital amplifier architectures have been developed that use Pulse Width Modulation (PWM) Class D output stages: 1. Analog PWM plus DAC; 2. Incremental Accumulated PWM; 3. Sub-ranging PWM. Figure 4 shows a comparison of several key product attributes for several digital amplifier architectures used in high definition flat panel TVs.
Figure 4: Comparison of performance of various types of digital amplifiers
Traditional analog PWM Class D amplifiers require an analog input and rely on a DAC to interface with the digital signal from the SoC. If the DAC is integrated in the SoC, pay special attention to avoiding interference sensitivities and preventing signal degradation when routing these sensitive analog signals on the board. Although it is a popular choice for flat panel TVs because of the low cost of analog PWM amplifiers, audio fidelity performance is moderate because of limitations in switching high power MOSFETs with single stage switching voltages and is limited to approximately 13 bits ( 80dB).
Recently, digital amplifier designs have been introduced that use segmented PWM or incrementally accumulated PWM to drive a Class D amplifier output stage. The digital input interface typically uses a standard 3-wire I2S digital bus from the processor SoC, board design concerns are alleviated, and immunity to interference is improved. Design engineers gain greater flexibility and freedom by eliminating interconnect lengths and layout requirements close to digital SoCs.
Although typically more expensive than analog PWM amplifiers, incrementally summed PWM amplifiers suppress in-band quantization errors and linearize the output signal by using integrated feedback loops and noise shaping signal processing; this does provide better audio fidelity , about 15 bits (90dB). However, a common criticism is that the sound experience is a bit harsh and the tone is not correct.
Another design consideration involves suppressing electromagnetic interference (EMI) introduced from the amplifier output. The output signal of the digital amplifier is sampled data, which is changed at discrete time intervals. This interval is defined by the pulse repetition frequency (PRF), which produces harmonics that are the primary source of EMI. The incremental accumulation modulator uses a higher PRF to achieve improved audio performance, so special attention needs to be paid to EMI suppression.
Segmented PWM digital amplifiers can achieve more than 17 bits (>102dB) of accuracy and fidelity by avoiding nonlinearities due to semiconductor technology. By using a two-level digital-to-pulse width conversion scheme, this amplifier faithfully reproduces even the smallest audio signal, providing a soft, clear sound experience. Unlike delta-sigma modulation, the performance improvement brought by segmented modulation is not directly related to PRF, but rather to effectively eliminating EMI coupling from fidelity targets. More importantly, the segmented PWM amplifier is low cost and can be modified to integrate with other audio system interface functions.
Summary of this article
The explosive development of the digital lifestyle is now driving the integration of audio/video systems, and the digitalization of the architecture is driving down the cost of consumer electronics systems. Although the very steep price-performance learning curve over the past 10 years has been attributed to digital system-on-chip integration, the system interface capabilities now showcased the golden opportunity for investment and accelerated the price/performance curve. Because audio is a core part of consumer electronics, it is natural that the integration of system interface chips and amplifiers is critical to the audio fidelity that is important in the quality of the end product. Current system design engineers are adopting new choices on audio digital power amplifiers to bridge the technology gap and achieve a digital lifestyle that does not degrade audio fidelity.
Fiber Optic Field Connector,Fiber Optic Accessory,Optical Fiber Accessories,Optical Fiber Accessory
Huizhou Fibercan Industrial Co.Ltd , https://www.fibercaniot.com