Mobile phone enters Hi-fi era ADI audio solution detailed

Mobile phone enters Hi-fi era ADI audio solution detailed

With ViVo, Xiaomi and other domestic mobile phone brands all announced high-profile into the Hi-Fi era, the battlefield of the mobile phone circle began to expand into the field of high-quality audio playback. In fact, it is already a place where analog/mixed-signal chip manufacturers have been working for many years. Signal chain solution providers like ADI have been supplying chips to leading audio equipment manufacturers for many years. In the audio equipment around you, there may be ADI Inside.

The history of audio processing is a process in which people continue to reproduce nature. From the birth of the first recording device in 1859 to the emergence of Dolby Blu-ray HD audio in 2006, the quality of audio is getting closer and closer to the original sound. And audio players are also rapidly transitioning from analog to digital.

According to Stephen Wu, marketing manager of the Consumer Products Division of Analog Devices in Asia, there are two major trends in current audio equipment. One is wireless, represented by WiFi and Bluetooth, and the other is portable. Both are very concerned about ADI.

Mobile phones can be considered as an integrator of these two trends, so audio processing on mobile phones has reached a new level. In particular, this signal link from the processed sound to the earphone or external is the focus of the smartphone to achieve Hi-Fi sound quality. Wu Yanbin introduced that the current smartphone can be designed with a two-stage amplifier circuit to drive the headphones behind the DAC. For example, the first stage converts the current into a voltage, and the second stage amplifies the voltage to achieve two-channel and high-quality sound. .

In this section, ADI has a complete solution, implemented with DSP ADAU 1452, stereo Class D amplifier SSM3582, and operational amplifier AD4841 or AD4896.

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The ADAU1452 is a DSP containing a CODEC originally designed for the automotive market and is compliant with automotive specifications. It features fully programmable enhanced sound processing, 1.2V 32-bit SigmaDSP® processing core operating frequency of 294.912MHz, each sampling rate of 48kHz, exceeding 6144SIMD instructions. Its audio processing algorithm uses a sample-by-sample and block-by-block mode that can be used simultaneously for signal processing.

Why put automotive-grade DSP products into the consumer electronics market? Zhao Chuanqi, sales manager of Analog Devices' Communications and Consumer Customers Division, said that there will be differences in products that enter the automotive and consumer markets. But the product can pass the rigorous car test, and there is no pressure in the consumer market. Most importantly, the demand for audio in car audio and consumer electronics is essentially the same.

In fact, ADI has a clear product division for the different requirements of the audio market. Used at the high end is SHARC® DSP, used in the middle and high end is the Blackfin® DSP family, the mainstream product is the ADAU145x series, and the entry level is played by the ADAU17xx.

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The SHARC series features floating-point arithmetic, excellent core and memory performance, and excellent I/O throughput for sound analysis, compensation, and sound effects. Many international brands of OEMs and ODMs use it for design. The ADAU1452 is a SigmaDSP®-specific series optimized for audio. Although it does not have floating-point arithmetic, it is very fast, and it is very easy to implement audio link design with the graphical programming tool SigmaStudioTM.

SigmaStudioTM must be mentioned here, which is a very powerful graphical programming tool. It has a huge resource, where users can select the desired dynamic processor, mixer, DSP, filter, and drag and drop directly to complete the design.

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According to Wu Yanbin's introduction, SigmaStudioTM is widely used in the design of car audio. Because the combination of components inside the car is very complicated, it will cause different actual sound effects. Using SigmaStudioTM, it is simple and convenient to call different components for testing. SigmaStudioTM can meet the needs of low-end to high-end product development. Many steps in hardware design can be used to implement it. For example, the width of the sound field can be used for debugging.

In this scheme, the Class D amplifier SSM3582 is also very important. Because the DSP processed digital signal is converted to an analog signal via it. The quality of the conversion directly affects the sound quality. The SSM3582 has the highest SNR on the market, the lowest THD, and very low quiescent current, which are key to ensuring high sound quality.

As mentioned earlier, the drive headphones can be dual staged. Analog Devices' AD4841 and AD4896 are ideal for preamplification. The AD4841 allows the sound to be unobtrusive and achieves a predefined tone, while the AD4896 delivers a cheerful, delicate and highly penetrating vocal. Why are the "personalities" of these two products so obvious, because "the requirements of the two levels for the op amps are not the same, the first level is usually more concerned with the performance indicators, to make this performance as good as possible, signal noise Compared with the improvement, the driving ability of the second level is the key,” explains Zhao Chuanyu.

ADI is a complete audio processing solution based on its deep accumulation and is in the leading position in the domestic mobile audio market. At present, seven of the top ten mobile phone manufacturers in China have used ADI solutions. The market situation is great, but what will ADI look like for the speed of this mobile phone audio processing upgrade?

In this regard, Zhao Chuanqi believes that "from the point of view of the indicators, now whether it is the flagship product of vivo, the latest release of the millet note is also good, in the main indicators can achieve the level of entry-level music player, previously needed to spend The price of the last four digits, but now you can enjoy this effect on your mobile phone. So, from the perspective of technology evolution, it is foreseeable that portable music players should be eliminated by mobile phones soon."

He also stressed that "Apple, Samsung and other mobile phone manufacturers have not introduced Hi-fi, does not mean that this is not the development trend of technology. As long as each manufacturer finds a correct positioning, there can be a good market. See many manufacturers to Hi-fi is a selling point, and from this point I am very optimistic about its prospects."

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