Solving Mixed-Signal Semiconductor Challenges with an Integrated Approach

Due to the significant increase in electronic devices in automotive and industrial applications, the automotive and industrial markets continue to play an important role in China's electronics industry, which continues to grow rapidly.

It is worth noting that in terms of electronic design, there are more and more common requirements between the automotive and industrial fields. For example, due to the increasing number of sensors, many applications in both fields now rely on complex information processing, while the demand for precise motor control or electromechanical actuators such as relays has become very common. Networking is also an area that is growing significantly. In-vehicle network (IVN) standards such as CAN and LIN are now used in both automotive and industrial designs to connect sensors, actuators and processors with related control and management functions.

Finally, both automotive and industrial applications are required to provide long-term reliable operation in a variety of harsh and demanding environments. Such environmental conditions include temperature, vibration, electrical noise, and in many cases, high voltage operation.

Mixed Signal Semiconductors

Faced with the pressure of implementing new designs within short cycles, tight budget control, and using the minimum number of components in an increasingly smaller space, designers are looking for ways to move from traditional discrete component design to more integrated semiconductor devices. This has led to a growing demand for system-on-chip ASICs and ASSP devices that integrate analog and digital functions on the same chip using mixed-signal semiconductor technology.

True mixed-signal technology requires isolating higher voltage, noise-sensitive circuits from lower voltage, noisy digital circuits, which can be achieved using deep trench isolation technology. In this technology, a series of isolation trenches are buried deep in the chip substrate, effectively forming on-chip "pockets" that can well control noise and power parameters. Traditional mixed-signal technology can combine control and signal processing functions such as amplifiers, ADCs, and filters with digital functions such as microcontrollers, memory, timers, and logic control. However, to meet the needs of emerging automotive and industrial designs, mixed-signal processing capabilities must go far beyond these. Today, mixed-signal semiconductor manufacturers face many challenges. They must combine the relevant functions of traditional mixed-signal design with various technologies to ensure high-voltage and high-temperature operation, provide high levels of electromagnetic interference and transient voltage resistance, and provide products that meet the quality and safety requirements of relevant industry organizations, and meet the above requirements at the lowest cost and seize the best time to enter the market.

Furthermore, the basic functionality of traditional mixed-signal devices must be expanded significantly in areas such as embedded intelligence, memory, common network controllers and interface availability, and direct actuator outputs if the needs of today's automotive and industrial engineers are to be met.

High Voltage Smart Power

High voltage performance is a key requirement for many mixed-signal devices used in automotive and industrial applications, whether they are motor control, relay drive, or simply require the ability to withstand high voltage transients. Fortunately, there are many high voltage mixed-signal semiconductor processes that can meet this requirement.

Taking AMI Semiconductor's I3T80 Smart Power process as an example, the I3T80 process based on 0.35mm CMOS can operate at 80V, enabling system designers to use chips with highly integrated digital circuits, high-voltage circuits, and high-precision analog modules, reducing the number of components, saving space, and reducing costs.

This high-voltage process allows gate density up to 15,000/mm2 and includes a full range of high-voltage DMOS and bipolar devices, including high-performance vertical floating nDMOS transistors. In addition, this process also uses NPN and PNP bipolar devices, high-voltage floating diodes and a variety of passive devices, and provides IP function blocks for designers who want to use AMIS process design and need options such as PLL, USB interface, bus protocol controller, controller for network connection, embedded microprocessor, etc.

AMIS Smart Power uses metal-metal capacitors and well-matched high impedance resistors. Electrostatic discharge (ESD) is an important aspect of product development, and the 4.5kV HBM (Human Body Model) and 750V CDM (Charged Device Model) ratings can meet the most demanding requirements.

Processor and Memory

One trend in mixed-signal circuits is to add some type of central processing circuitry, making the AMIS I3T80 process suitable for options such as the ARM7TDMI, R8051, and 6502 cores. Furthermore, with the need for on-chip processing comes the need for on-chip data and program storage. Volatile storage structures such as data latches, registers, and RAM are typically used, but require continuous power to retain data. However, newer mixed-signal designs use non-volatile memory (NVM) options including OTP or EEPROM for factory programming, and more recently, flash memory options. For example, AMIS has developed embedded high injection MOS (HiMOS) flash for its I3T80 Smart Power high-voltage mixed-signal system process technology. The combination of mature I3T80 mixed-signal technology and powerful new NVM will enable designers to create economical smart sensor interfaces, smart actuators, and other advanced single-chip devices for the harshest automotive and industrial operating environments.

HiMOS flash memory is capable of operating in the -40℃~125℃ temperature range. It enables designers to embed dual-bank memory, one bank of which is up to 64kB of code storage and the other bank is up to 512 bytes of virtual EEPROM data storage. Since AMIS HiMOS flash memory is implemented using only three additional mask layers on the I3T80 basic process mask set, this flash-based intelligent Smart Power chip provides a very economical choice for discrete components and other SoC alternatives.

HiMOS flash memory provides up to 100 code storage erase cycles and a minimum of 10,000 data storage erase cycles. It can retain data for 15 years and fully meets the requirements of AEC-Q100 critical stress test for automotive electronic components.

Network and communication capabilities

Building a network requires physical layer (PHY) implementation and demands special attention to issues such as electromagnetic interference immunity, bus short circuit protection, and prevention of network communication blockage. Designers have often had to consider providing these features themselves, but the latest mixed-signal semiconductor technologies offer an alternative approach.

Of particular interest in this regard are the LIN, I2C, SPI and CAN network standards, the latter of which has become a very common standard in automotive and industrial design, serving as the interconnection foundation for servers, sensors, controllers and a host of other devices used for in-vehicle networking, mechanical control and automation. Therefore, mixed-signal semiconductor manufacturers must provide CAN and LIN functions in the form of off-the-shelf ASSPs or IP blocks for integration into ASICs.

Solving EMC problems

With the increase in automotive and industrial electronic devices, electromagnetic compatibility (EMC) issues are becoming more and more of a design challenge for engineers. Three of the main issues are: how to minimize electromagnetic sensitivity (EMS) to protect electronic devices from harmful electromagnetic emissions (EME) caused by other electronic systems; how to protect electronic devices from harsh environments, including power system transients or interference from large or inductive loads such as switching lights and motors; and how to minimize electromagnetic radiation that may affect other electronic circuits.

Moreover, these problems become more prominent as the system voltage increases, the number of digital electronic devices increases, and the frequency increases brought by more high-frequency electronic devices. In addition, many electronic modules now connect low-power, cheap sensors with low linearity and large offset. The signal amplitude of such sensors is small, and the impact of electromagnetic interference can be catastrophic to their operation.

The key thing to note here is that radiated emissions and susceptibility are not the primary issue with the integrated circuit. Rather, it is the conducted emissions and susceptibility created by the effective antennas on the PCB and wiring harness that are the key issues.

In developing system-on-chip devices based on its own mixed-signal semiconductor processing, AMIS assists engineers in various ways to ensure that their final designs meet EMC requirements. For example, for EME generated by DSP switching, clock drivers, and other high-frequency currents, low-power circuits should be used whenever possible. This may include using reduced or adaptive supply voltages, or using an architecture to spread the clock signal in the frequency domain. EME can also be reduced by reducing the number of switching elements in the same clock cycle. In addition, slowing down the switching speed by implementing slope control on the clock and driver signals to provide softer switching characteristics can also help reduce EME. External and chip layout should also be carefully studied. For example, differential output signals using twisted pairs generate less EME and are less sensitive to EME. Ensuring that VDD and VSS are close to each other and using efficient power supply decoupling are also simple ways to reduce EME.

Rectification/pumping, parasitic devices, and current and power dissipation are the three most serious interference effects for high EMS. High-frequency electromagnetic power is partially absorbed by the integrated circuit, which can cause various interferences. These include outputting high-frequency voltage to high-impedance nodes and high-frequency current to low-impedance nodes. PCB design varies from application to application, and there is a subtle relationship between product and PCB design, so it is critical that system and integrated circuit engineers work closely together to minimize its impact.

Mixed-Signal ASICs and ASSPs

AMI Semiconductor has used these technologies and methodologies to create a foundation for the development of ASIC and ASSP devices that meet the integration, functionality, performance, voltage, temperature and environmental requirements of industrial and automotive applications.

Sensor Interface ASIC

Driven by the increasing complexity of today's systems, more intelligent functions are being integrated into sensor elements. Now, the advances in process design as described above have reached a level that can achieve this level of integration. Sensor interface ASIC solutions can transform an ordinary sensor into an intelligent sensor. The focus must be on the best methods for adjusting, converting and processing signals from sensor elements (also including intelligent sensor interfaces such as temperature detection, Hall effect detection, calibration and diagnosis).