Analog technology and digital technology complement each other in digital equipment

Tags: digitization, analog technology, digital technology

1. Introduction

The ability of digital electronics to quickly and accurately collect image, voice and audio data from our surroundings and manage and control this data in the digital domain has enabled communications at any time and any place, thereby improving computing performance. Digital electronics have also produced more reliable and cheaper medical electronics, and it has brought exciting, interactive multimedia content to a variety of consumer devices. Overall, these advances have put the world we live in under digital control and management.

2. Analog technology plays an important role in digital electronic devices

The trusted advantages of digital technology in digital electronic devices can only be realized if it is as good as the ability of analog technology to correctly restore the digital signals represented by "1" and "0" to the analog signals that people can hear, see, feel or perceive. Without significant and simultaneous innovations in analog technology, the effects of the digital revolution may be eclipsed. The more information we capture digitally, the more data we must convert and restore - whether it is real-time voice transmission, audio signals or video images. Today, such as cellular phones that continue to reduce size and increase feature sets, the sound quality of high-end car audio systems and the high-definition (HD) images of broadcast digital television are not only the product of smart circuit design, advanced manufacturing processes and high-performance digital processing technology, but also the product of continuous innovation in analog design. For example, high-speed digital signal processors (DSPs) enable digital audio receivers to improve their performance by adding multiple audio channels. However, each new channel requires a separate power amplifier to drive the output signal in a way that is easily distinguishable and comfortable to the human ear, as shown in Figure 1, and the following explanation is given.

2.1 Figure 1 shows the all-digital audio components and the digital + analog audio solution.

Figure 1 is its composition block diagram

To meet the needs of today's digital audio device market design, the all-digital audio components in Figure 1 and the digital + analog audio solutions are used. The superior performance and design applicability of programmable components allow designers to build an audio system with more functions and a more realistic sound experience at a more competitive price. Its analog + digital signal processing (DSP) solution can be a combination of industry-leading digital signal processing (DSPs), high-performance analog devices, logic, and extended application software, which will provide the most reliable, accurate, and high-performance solutions for audio designs from the most complex to the simplest.

The rapid growth of digital electronic devices has actually driven the demand for analog ICs even more. In many cases, new digital products require new levels of high integration and high performance analog ICs to be able to convert (see Figure 2 High-performance 24-bit, dual/quad-channel stereo audio analog-to-digital converters), condition and stabilize signals, and control and power the links that determine today's advanced system functions.

2.2 Main features of high-performance 24-bit, dual/quad-channel stereo audio analog-to-digital converters (ADCs) PCM4202 and PCM4204.

Figure 2 is a block diagram of the components of PCM4202 and PCM4204.

The PCM4204 is a high-performance, four-channel ADC designed for professional audio applications. It supports 24-bit linear pulse code modulation (PCM) output data with a sampling frequency of up to 216kHz. It can also be configured to output single-bit direct stream digital (DSD) data with 64x or 128x oversampling for two channels. The PCM4204 is also ideal for DVD-Audio and Super Audio CD (SACD) recording applications.

Applications: Can be used on professional studio equipment and DVD-Audio and Super Audio CD (SACD).

In fact, due to the innovation of analog technology, consumer terminals have acquired many functions of digital products. Here, we will illustrate this with examples of application trends.

3. Observe from the example of application trend that analog technology promotes and determines the prospect of digital technology

3.1 Advances in data converter technology have led to breakthroughs in the performance of digital still cameras (DSCs)

While advances in DSP and microcontroller (MCU) processing technology have provided the bandwidth required to quickly process images digitally, the quality of those images depends on the ability of high-performance data converters (ADCs) in the digital camera analog front end (AFE, see the DSC block diagram in Figure 3) to reduce noise and increase dynamic range. Advances in data conversion technology have also enabled the AFE to address other common performance issues. For example, reducing power consumption to extend battery life, increasing the analog-to-digital conversion sampling rate to increase camera shutter speeds, and increasing the light sensitivity of image sensors to reduce the flash requirements of high-resolution cameras.

Figure 3 is a block diagram of a digital camera. It can be seen from Figure 3 that the camera analog front end (AFE) and high-speed ADC will bring about a breakthrough in improving DSC performance.

In addition, analog technology innovations not only improve the performance of digital cameras, but also help produce a variety of new digital camera designs. For example, analog technology is combined with micro-electromechanical system (MEMS)-based sensors to avoid blurry photos by adding gyroscopes and data conversion technology to compensate for camera "shake".

3.2 Audio Codec in Digital Audio Processing is the Key to Fully Unleashing the Performance of DSP

Whether processing Dolby 5.1-channel surround sound in home theater applications or 12-channel audio in high-end automotive systems, today's audio signal chains are becoming increasingly digital. However, in reality, the signal chain is only "all digital" in name only, because the large amount of multi-channel audio has put new performance requirements on analog technology. For example, the inherent digital signal processing challenges in multi-channel digital audio structures require designers to use multiple high-performance analog power amplifiers to drive the speakers (as can be seen in Figure 4) and audio codecs that can convert analog audio signals without sacrificing, or "giving up" DSP performance.

3.21 Dolby 5.1 channel surround sound home theater AV receiver.

Figure 4 is a block diagram of an AV receiver

The AV terminal equipment can utilize DVD audio and SACD high-quality audio formats and not only provides the highest performance, but also provides customers with the most economical solution. Aureus audio DSP provides processing capabilities for various audio decoding formats; Burr-Brown audio data conversion products support both the highest-end and the cheapest systems with their full range of performance. As can be seen from Figure 4, it uses multiple high-performance analog power amplifiers-stereo digital power regulation amplifier controllers TAS5182 (for analog power amplifiers with higher performance) to drive speakers and audio codecs PCM1850 that can convert analog audio signals. Therefore, this home theater AV receiver has a high-speed transmission rate with excellent analog characteristics throughout the entire audio signal path. [page]

3.22 Main features of the stereo digital power regulation amplifier controller TAS5182.

Figure 5 is the block diagram of TAS5182

TAS5182 is a high-power stereo digital audio amplifier driver from TI. When the power amplifier is 150W (RMS), the THD+N can be less than 0.1%.

*Main features: Stereo half-bridge (H-Bridge) drive; high power output: 150W 4Ω load RMS state, total harmonic distortion + noise (THD+N) less than 0.1%; 100W 6Ω load RMS state, total harmonic distortion + noise (THD+N) less than 0.1%; 90W 8Ω load RMS state, total harmonic distortion + noise (THD+N) is less than 0.2%; full power range 20-20kHz total harmonic distortion + noise (THD+N) is less than 0.10%; with error reporting self-protection settings (including low voltage, over temperature, short circuit protection); excellent audio characteristics when used in conjunction with TAS5518, signal-to-noise ratio (SNR) is 110dB and total harmonic distortion + noise (THD+N) is 0?% (typical); supports sampling rates from 32kHz to 192kHz; low electromagnetic interference design is achieved through necessary voltage regulation; no pops and cicks

*Applications: AV receivers, DVD receivers, active low frequency amplifiers, micro/portable components and car digital amplifiers.

In addition, in many applications, the introduction of multi-channel audio into smaller and smaller systems requires low-power and low-cost analog ICs that can operate at high efficiency. Even mass-produced consumer audio systems require state-of-the-art audio converters to ensure the high performance and precision required for digital processors to achieve maximum performance.

3.3 New models of “digital” cellular handsets drive demand for new analog features

As cellular infrastructure upgrades from 2G and 2.5G to higher performance 2.75G and 3G services, a new generation of smarter, more feature-rich mobile phones is being developed. The rapid convergence of voice, video and data allows the addition of exciting features such as MP3 or MP4 music and broadcast television in the next generation of mobile phones. The cellular handset market has been developing in various directions as manufacturers divide their product lines to meet the needs and habits of different users.

However, the features in these "digital" cellular handsets are also driving the need for new analog functions. For example, the trend toward integrating high-resolution cameras into wireless handsets requires improvements in the performance of analog image processing, image stabilization, focus and zoom control, and the data converters and amplifiers necessary to support these functions.

Furthermore, new cell phones with easy-to-read color displays and more user-friendly interfaces require advanced liquid crystal display (LCD) backlight power devices (see Figure 6). And as designers integrate new voice, video, and data capabilities into these platforms and manage up to 20 different regulated voltages, advanced power management and battery charging ICs are also needed to ensure that improved camera performance does not reduce battery life.

3.31 Typical application of TPS65120 bias power supply for LCD and OLED displays.

Figure 6 is a typical application diagram of TPS65120

The quad-output power supply TPS65120, which is used to simplify the structural factor of TFT displays, is one of the bias power supply series for LCD and OLED displays.

3.311 Its main features

*Key output voltage parameters VMAIN: adjustable voltage, 3.0V to 5.6V/25mA; post-regulation to reduce ripple (5mVpp); ±0.8% typical precision positive output, VGH; voltage regulation up to 20V/2mA; ±3% typical precision negative output, VGL, voltage regulation down to -18V/2mA; ±3% typical accuracy.

* Complementary 1.8V/3.3V linear regulation.

*Automatic or programmable power supply sequence.

*2.5V to 5.5V input voltage range.

*Output short circuit protection.

*Package mode: 16-pin QFN package (3×3×0.9mm)

3.312 Scope of application

It can be used in cellular phones, smart phones, PDAs, microcomputers PCs, portable DVDs, digital still cameras (DSCs), and digital video cameras.

These demands, combined with the challenges involved in implementing the advanced multi-band, multi-mode radio frequency (RF) and analog interface functions required by the basic communications engine in 3G handsets, will cause the average analog IC cost in wireless handsets to rise from approximately $8 today to more than $15 in the near future.

3.4 Medical image processing applications are particularly prominent, and its application in magnetic resonance imaging (MRI) is a typical example.

In the healthcare field, the availability of a large number of digital technologies and the transition from fixed systems to portable devices are driving the demand for a variety of new high-performance analog ICs. For example, in medical image processing applications, high-speed digital computing allows doctors to observe high-resolution CT scan images and ultrasound images to assess the status of important organs or blood vessels more quickly and accurately. However, in order to cleverly utilize these new features, the signal acquisition capabilities of its products must be enhanced by increasing channel density and improving AFE (analog front end) performance.

Recent advances in programmable variable gain amplifiers and analog-to-digital converters (ADCs, see Figure 7(a)) have increased dynamic range and improved image quality. At the same time, quadrature (I/Q) demodulators and phase shifter ICs have improved the performance of Doppler ultrasound systems. In addition, by integrating multiple functions and multiple channels into a single chip, these high-performance analog ICs help design engineers build smaller and more portable systems because they significantly reduce the product's size and power consumption.

3.41 Main features of the 4-bit 125MSPS ADC ADS5500 and its application in magnetic resonance imaging (MRI)

* Figure 7(a) is the functional block diagram of the 4-bit 125MSPS ADCADS5500

The ADS5500 provides a complete converter solution. It includes a high-bandwidth linear sample-and-hold stage and an internal reference. Designed for applications that require extremely high speed and dynamic performance in a very small space, the ADS5500 features low power consumption of 780mW and uses a single 3.3V supply voltage. The device provides an internal reference, and parallel CMOS-compatible outputs ensure seamless connection with common logic circuits.

* The application of ADS5500 and high-speed current feedback amplifier in magnetic resonance imaging (MRI) is shown in Figure 7(b).

ADS5500 can be used in the design of medical MRI equipment. Its 14-bit resolution provides a high SNR, which enables designers to reduce the magnetic field energy required to achieve high image quality. In addition, the sampling rate of 125MSPS also creates conditions for oversampling, which also helps to improve image quality and simplify filter requirements. In addition, ADS5500 can also be used in test and measurement instruments, single-channel and multi-channel digital receivers, and video and imaging.

3.5 The adoption of new analog technologies has driven the development of advanced television

Although the advent of high-definition television and cinema-quality sound is due to the digital revolution, the adoption of new analog technologies and innovations in digital design have also driven the development of advanced television. Even in the era of digital broadcasting, televisions still need two interfaces, digital and analog, to support traditional video recorders (VCRs), DVD players and camcorders. Highly integrated interface ICs that can support multiple interface standards, from standard analog interfaces to the emerging high-definition multimedia interface (HDMI) - will be applied and meet the needs of connecting from analog or digital input to advanced flat-panel displays. [page]

High-performance audio processors will help transfer the task of analog sound processing to the digital domain, and new highly integrated post-processing ICs can improve audio quality by compensating for the limitations of thin flat-panel TV designs. Here, the audio signal path of a plasma display TV (see Figure 8(a)) is used as an example. As can be seen from the plasma display TV audio signal path in Figure 8(a), the high-efficiency Class D audio power amplifier solves two problems of flat-panel display audio with higher power: heat dissipation and power consumption. Low heat dissipation eliminates the need for large heat sinks. Low power consumption effectively reduces the size and cost of AC/DC power supplies. Similarly, these advantages also make flat-panel displays as thin and light as possible.

*20W Stereo Class-D Audio Amplifier TPA3100D2 Main Features

Figure 8(b) is a schematic diagram of TPA3100D2 application

The TPA3100D2 is a high-efficiency Class D audio power amplifier designed to drive bridge-tied stereo speakers. The TPA3100D2 can drive stereo speakers as low as 4Q. When playing music, the high efficiency (92%) of the TPA3100D2 does not require an external heat sink. Its main features are: high-efficiency Class D operation; wide operating supply voltage of 10V to 26V; 4 integrated gain settings; thermal protection, short-circuit protection and error reporting.

Application: In addition to plasma TV (PDP), it can also be used in CRT, digital light processing TV (DLPTV) and liquid crystal TV (LCDTV).

4. Conclusion

From the above analysis, analog technology is the data conversion technology and front-end signal processing technology required to control and manage various physical phenomena in the real world (such as images, light, sound, motion, pressure and temperature). It is very important and indispensable for creating a valuable and new type of digital terminal (equipment). Therefore, designing and developing analog signals, digital signals and mixed signal technologies and improving integration, reducing package size, reducing power consumption and reducing system costs are the key to meeting the mass market cost structure that can make digital design popular. Therefore, as a designer, you should choose the right IC to bring the full potential of its digital design to real life.