New storage requirements from EE architecture evolution and industrial robot development

As the research and development of the automotive industry continues to move forward, and the EE architecture itself evolves, regional computing power has been improved and combined with cloud computing. In this context, edge computing processing has become a necessity for the next generation of cars. Complex and efficient interconnection capabilities and integrated systems inside and outside the vehicle are vertical integration technologies that every car company focuses on investing in. And the key information needs to be recorded by the EDR (Event Data Recorder), a data recording system that can reproduce the accident process. This so-called "car black box" mainly records the key operating data of the car in three different stages before, during, and after the collision, such as driving speed, steering wheel steering speed, vehicle braking status and other parameters, to provide objective and accurate data for the investigation and analysis of traffic accidents.

The development of automobile technology requires the use of memory in electronic systems. So what is the role of memory here? Which memories are worthy of attention and selection?

Figure 1. Automotive memory requirements under EDR

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Record requirements for automobiles

EDR: Event Data Recorder, refers to the automobile event data recording system, which is used to record the key operating data of the vehicle in the three stages before, during and after the collision. EDR is used to record the driving data of the vehicle when an accident occurs, and its parameter information mainly comes from the bus and others. The EDR system is mainly composed of collision sensors, CAN modules, control storage units and other parts. There is a large amount of key data in the car that needs to be stored, and this data plays a particularly important role in tracking accidents.

The control storage unit is the core of the EDR system. It is required to be able to receive the accelerometer and vehicle CAN bus status, store it in its own memory, and lock it in the on-chip Flash memory. This requires the control unit to have a faster processing speed and larger RAM and Flash space.

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Storage requirements for cars

Memory for applications in this area has to meet high demands. First and foremost, the storage system must be able to survive a vehicle accident - since a collision could cause the car's low-voltage system to lose power, the storage requires a native non-volatile memory that can save data without being connected. In addition to this, the storage of the recorded data must meet some strict conditions.

2.1 Basic Requirements for Automotive Memory

1) Non-volatility: This is a basic requirement, the data must be recorded

2) Survivability in harsh environments: After a collision, the data in the memory must be preserved

3) Working time and lifespan: The life cycle of a car is very long, and the memory needs to be able to work even after the car is old.

4) Low power consumption: If the power consumption is too high, it will be difficult to design a preservation mechanism

5) Fast flashing: The collision time is very short. If the power is off, the data needs to be written quickly.

2.2 What are the differences between the different features?

Today's storage devices have higher and higher requirements for fast flashing and writing. From Flash, EEP to F-RAM, the technical standards of automotive memory are constantly changing, and the main dimension is still faster flashing. For automatic assisted driving systems, it is very convenient to save data quickly. F-RAM memory (combining the advantages of RAM and ROM) has more advantages than EEPROM, mainly because it does not require a write waiting time and can store important data almost in real time (actual 10us storage time); in contrast, EEPROM usually requires a write waiting time of more than 10 milliseconds.

Of course, in this application, it is also necessary to have no write delay and high speed to be suitable for applications that need to write large amounts of data quickly. When writing one or two bytes to a random location in the memory, the write cycle is about 1 microsecond, compared to EEPROM or flash memory, which requires a write cycle of about 5-10 milliseconds.

Figure 2 Comparison of F-RAM and EEPROM writing data

The basic principle of FRAM (Ferroelectric RAM) storage unit is ferroelectric effect. It is a ferroelectric memory device that uses the spontaneous polarization form of ferroelectric film to store data. FRAM controls the spontaneous polarization of ferroelectric capacitors through an external electric field.

Figure 3 FRAM technology

Traditional writable non-volatile memory derived from floating gate technology uses a charge pump to develop on-chip, which allows carriers to pass through the gate oxide layer, resulting in long write delays, high write power, and write operations that are actually destructive to the memory cell. Floating gate devices cannot support writes that exceed 10^6 accesses, while the number of writes for FRAM can reach 10^10, which is more than 10,000 times higher than the 10^6 times of EEPROM.

FRAM is far superior to floating-gate devices in both write speed and power. For a typical serial EEPROM clocked at 20MHz, it takes 5ms to write 256 bits (32-byte page buffer) and 1283.6ms to write the entire 64Kb. For an equivalent FRAM, 256 bits takes only 14µs and the entire 64Kb takes only 3.25ms. In addition, writing 64Kb to an EEPROM requires 3900µJ, while writing 64Kb to an F-RAM requires 17µJ, a difference of more than 229 times.

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Excelon F-RAM Memory

The company has launched the industry's highest density 1Mbit-16Mbit Excelon F-RAM memory (ferroelectric memory), which supports the QS interface, a maximum clock of 108Mhz, and a maximum read and write rate of 54MB/s. This helps prevent data loss in harsh operating environments by meeting the permanent data acquisition requirements of next-generation vehicles and systems.

FRAM (Ferroelectric Random Access Memory or FeRAM) is a self-contained nonvolatile memory that instantly captures and saves critical data when power is interrupted. They are ideal for mission-critical data logging applications, such as high-performance MCUs (), or life-extending patient monitoring equipment that require high-reliability control and throughput. Designed in a low-power, small form factor, F-RAM provides instant nonvolatility and virtually unlimited endurance without compromising speed or energy efficiency.

Figure 4 Comparison

3.1 Application Scenarios of Automobiles

In the entire usage scenario, the application of memory widely covers the data brought by various sensors, such as automatic assisted driving, instrument system (mileage and key information), battery management system, driving recorder, entertainment system and gateway system. In fact, if the design is sophisticated, this kind of memory can be used in many places.

3.2 Main advantages

With its advantages in high-speed reading and writing, high reading and writing endurance, low power consumption and tamper-proofing, FRAM can find more suitable applications in the field of automotive applications and can replace traditional EEPROM products.

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F-RAM Industrial Applications

In industrial equipment, due to the long product life cycle, long-term technical support is required, and some product applications can even last up to 20 years. Since FRAM is more reliable than EEPROM and has several orders of magnitude higher write times than other non-volatile memories, it is a more ideal memory in the industrial field. Taking industry as an example, on the one hand, manual tasks can be performed efficiently, accurately and repeatably, and on the other hand, robots are now becoming popular in factories and commercial facilities. Smart factories have put forward more requirements and need to be able to collect and analyze data about themselves to improve productivity, service quality and reliability, while reducing the overall total cost of ownership.

From a reliability perspective, industrial robots must be able to recover from a variety of power events, and once power is restored, the software system inside the robot has been reset, and the robot can immediately resume operation from where it stopped. Each unit must be able to save key parameters and data states, including the rotation angle and position of the arm. Similarly, the controller needs to maintain a detailed control log that records the operating parameters of each axis, including its command position, value, and payload. In addition, the controller must keep records tracking speed, torque, motor feedback sensing (i.e., position, speed), and angle of motion. Reliably recording all of this data requires some form of non-volatile memory so that the data is not lost due to power outages.

This is a very important application scenario. Here, Infineon FRAM products include various interfaces and multiple densities, such as industrial standard serial and parallel interfaces, industrial standard packaging types, and densities such as 4Kbit to 4Mbit, which have good industrial application scenarios. In addition to being used in the above-mentioned industrial robots, it is also widely used in medical monitoring, environmental monitoring, aircraft, transportation and other fields. FRAM does not require wear leveling, external batteries, and the design of storing key data in FRAM has become the mainstream implementation method in the device; ensuring that the breakpoint process data can be reproduced at any moment of an accident, ensuring equipment and production safety, and reducing losses. The battery-free design also eliminates the need for spare parts maintenance for the equipment, reducing operation and maintenance costs.

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Summary: Characteristics of F-RAM memory

In fact, F-RAM has unlimited endurance combined with its real-time, non-volatility, high throughput and reliable data capture, making it a strong choice for non-volatile memory for high-performance data logging in automotive and industrial applications. Since F-RAM can ensure data can be saved in various power-off accidents, it is indeed a good memory choice.