As car intelligence is accelerating, Rohm builds a high wall for safety

With the advancement of automobile intelligence and the rapid innovation of autonomous driving technology, safety has become the focus of the industry. There are two types of safety, one is intrinsic safety and the other is functional safety. Intrinsic safety is a method of ensuring safety by eliminating the causes of danger; while functional safety is a method of ensuring safety by reducing risks to an acceptable level through functional efforts. Intrinsic safety can ensure absolute safety, but the cost is often high; in contrast, the cost of functional safety is lower, but the design must take into account how to ensure safety when the additional functions fail.

For example, at a railway and road intersection, if you use the method of building an overpass to separate the railway and the road, and physically avoid collisions between trains and cars, this is an intrinsically safe idea. And if you install sirens and railings at the intersection of roads and railways, and install sensors on the railway, when the sensor detects that the train is approaching, the siren will sound and the railings will be lowered. When another sensor detects that the train has passed, the alarm will sound. Although the road and the railway still physically cross each other, the risk of collision between cars and trains can be reduced to an acceptable level by setting up railway crossings. This is the idea of ​​functional safety. Of course, in this case, if the sensor is damaged, the alarm and railings will not work when the train approaches. This is a "dangerous" state, so it is necessary to add self-diagnosis of the sensor or a redundant design of dual sensors. , to ensure that even if the sensor is damaged, it will not cause a dangerous state. This is the idea of ​​​​Fail Safe.

It can be seen that functional safety is actually a design based on the idea of ​​"people make mistakes" and "things get damaged", and functional safety usually takes into account both "systemic failures" and "random failures". , to ensure that there are no systematic bugs and that random failures will not cause harm to people. In China, ISO 26262 (functional safety) has been included in the recommended national standard, and the first Chinese translation of ISO 26262, GB/T 34590, has been implemented since May 2018.

Of course, this requirement is not limited to the automotive field. Many industrial scenarios also have very high safety requirements. In order to build a safer system, it is necessary to consider how to ensure safety when problems occur during the device development process, which means that fault safety and functional safety are throughout the entire device development process.

When talking about the demand for equipment safety in automotive and industrial application scenarios, we have to mention the importance of monitoring the system power supply voltage. The reset IC is one of the indispensable products in the voltage monitoring circuit. It has been widely used in various automotive and industrial equipment applications that require voltage monitoring of electronic circuits, such as EV/HEV inverters, engine control units, ADAS, car navigation systems, car air conditioners, FA equipment, metering instruments, servo systems, various sensor systems, etc.

So what is a reset IC? A reset IC is a switch IC that can be used for voltage monitoring in electronic circuits. When it detects that the monitored voltage exceeds the threshold, it changes the output to achieve the effect of the reset operation. Therefore, it has the function of ensuring system safety by cooperating with the microcontroller. It is like a water level alarm in a river. When the river water overflows the highest warning line or falls below the lowest warning line, the alarm will sound and trigger the release or storage of water. The water level sensor here is like the reset IC in the circuit, and the effect is the same.

Why are there so many types of reset ICs? What are the features or advantages of the latest reset IC "BD48HW0G-C" launched by Rohm? Due to different application scenarios, the system circuit has different requirements for reset IC accuracy, power consumption, operating voltage, functional safety, monitoring voltage range, undervoltage/overvoltage detection, etc., so different reset ICs need to be developed to match the corresponding market needs.

ROHM's latest reset IC "BD48HW0G-C" is a window-type reset IC that supports 40V voltage. Due to the use of high-voltage BiCDMOS technology and the integration of ROHM's expertise in analog design technology, BD48HW0G-C works The voltage range is wide and adjustable from 1.8V to 40V. Regarding the window-type design, since the BD48HW0G-C is equipped with two independent reference voltage circuits, the detection voltages on the High side and the Low side can be flexibly set and the detection outputs can be reset independently. In terms of detection accuracy, BD48HW0G-C can achieve the industry's advanced voltage detection accuracy of ±0.75% in the temperature range of -40℃-+125℃, which is higher than the accuracy of industry standard products of ±2.2%. In terms of power consumption, the quiescent current of BD48HW0G-C is only 500nA, which is only 1/16 of an ordinary window-type reset IC with an operating voltage above 24V. This allows engineers to design circuits without worrying about the increase in power consumption caused by the reset circuit. .

Figure | High-precision reset IC within full operating temperature range makes system design easier

Why do we need to emphasize stable high-precision characteristics within the full operating temperature range in the automotive and industrial fields? We know that if there is only a value deviation problem at 25°C, it can be easily achieved by adjusting it through fixed compensation. However, in automotive and industrial applications, the ambient temperature and the heating and heat dissipation of the fuselage itself vary greatly. The power supply voltage and reset detection voltage will fluctuate due to the influence of temperature. This deviation under the influence of temperature is very difficult to correct. Therefore, for automotive and industrial environments, choosing a stable high-precision reset IC within the full operating temperature range is easier for system design, thereby reducing the design burden of customers. In addition, in automotive and industrial environments, the environmental noise is usually large. When external noise invades, if the voltage detection accuracy is poor, it is easy to cause malfunction. Therefore, in order to avoid or reduce the influence of external noise and improve the reliability of system operation, a high-precision reset IC is a better choice.

It is worth mentioning that ROHM has started to build the ISO 26262 process since 2015, and obtained the ISO 26262 process certification through the German third-party certification agency TÜV Rheinland about two and a half years later, in March 2018. Because of its advanced understanding of ISO 26262 specifications and application circuits, ROHM has developed reset ICs that support a wide voltage range from low to high and detect voltage abnormalities with high accuracy for automotive and industrial power supplies that require functional safety.

As mentioned earlier, the quiescent current of BD48HW0G-C is only 500nA, which is only 1/16 of an ordinary window-type reset IC with an operating voltage above 24V. How is such ultra-low power consumption achieved?

In fact, ROHM adopts the IDM model. Under this vertically integrated production system, ROHM has deeper experience accumulation and stronger knowledge in the three aspects of "circuit design", "layout" and "process". Analog Technology Advantages. Based on this, ROHM has developed "Nano Energy™", an epoch-making technology that completely reduces current consumption under ultra-light load conditions. Using this technology, the quiescent current at no load can be as low as the nanoampere (nA) level, which not only extends the driving time of battery-powered IoT devices and mobile devices, but also helps automotive and industrial applications that do not want to increase power consumption. The equipment works efficiently.

For example, we know that new energy vehicles are an important part of realizing the global "double carbon plan". For EV/HEV, it is imperative to improve fuel economy and increase driving mileage, so low power consumption will become particularly important. Second, when the car idles and stalls, the engine stops and the battery provides the power needed to function. Furthermore, when parking, the clock running in the background, the alarm system turned on, the keyless system turned on, etc. will be directly powered by the battery, and there is a risk of battery exhaustion. Therefore, it is imperative to further reduce the current consumption of power supply ICs, and by incorporating Nano Energy™ technology, it can contribute to the low power consumption of the entire automotive system. In addition, low quiescent current not only brings the benefit of extending the life of battery-powered equipment, but also reduces dark current in the circuit for automotive and industrial applications, helping to improve EMC. More details:

https://www.rohm.com.cn/support/nano