Highly reliable high-side drives power automotive applications
In-depth explanation - Understand the challenges of high-side driving in automotive applications
With the development of automotive electronics technology, the demand for electrification, lightweight and intelligence has led to the large-scale application of automotive-grade high-side drivers (HSD) in vehicle body load drives.
In the field of automotive applications, high-side drivers are mainly used to drive and switch loads such as lights, valves, pumps, motors, etc., and monitor the short circuit and open circuit, current and voltage of the load during the switching process, and protect and protect the load. Diagnosis, at the same time, the high-side driver integrates the clamp shutdown function, which provides support for switching energy processing capabilities and does not require a freewheeling current recirculation path, thereby reducing design difficulty, reducing battery energy consumption, and saving system costs.
Currently, regarding high-side drivers, the automotive industry mainly focuses on its characteristics when driving resistive, capacitive, and inductive loads.
Among the three major load types, the simplest is resistive load (such as PTC, seat heating). Its load characteristics are relatively stable, testing the on-state resistance of the high-side driver. The lower the internal resistance of the high-side driver, the larger the resistive load it can carry and the higher the rated current it can carry.
Capacitive loads will generate large surge currents when starting. Taking the halogen lamp load as an example, the lamp load characteristics and surge current are usually described by three parameters: IDC, IINRUSH and tLAMP−ON. IDC defines the current consumption in the steady state, IINRUSH is the initial surge current, and the time constant tLAMP−ON describes the transition time to the steady state. It is generally believed that IINRUSH is 10 times larger than IDC. When the driving current drops to less than half of IINRUSH, the lamp reaches the on state, and this period of time is defined as tLAMP−ON. If the high-side driver has short-circuit protection and turn-on retry due to surge current, tLAMP−ON is defined as the time required from the beginning to the last turn-on retry. In the design of car lights, it should be ensured that tLAMP−ON does not exceed 30ms.. The surge current is mainly affected by the filament temperature. The worst case basically occurs at -40°C, and the typical case is at the ambient temperature (+25°C). The actual operating current is often much smaller than the surge current, so the current-limiting protection design for capacitive loads is a challenge.
The most complex is the inductive load. Common inductive loads in automotive electronic systems mainly include: actuators in transmission control module (TCU) applications, such as motors, solenoid valves, etc.; actuators in body control modules (BCM), such as wipers, relays, fans, and water pumps. , oil pumps, etc., also show perceptual characteristics. When the high-side driver responds to the shutdown of an inductive load, it needs to maintain the current flow direction of the inductive load through freewheeling protection. However, if the voltage polarity at both ends of the load suddenly reverses, the high-side driver output will instantly generate hundreds of volts of negative voltage.Since the amplitude of the turn-off negative voltage is positively related to the demagnetization energy in the inductive load, the DS terminal of the MOSFET inside the high-side driver will bear a huge reverse voltage. If no clamping measures are taken, the MOSFET will face the risk of being damaged.. At the same time, whether the demagnetization dissipated energy generated by instantaneous shutdown is within the tolerance range of the high-voltage side device also determines whether demagnetization shutdown will burn the high-side driver.
So in order to meet these load driving challenges, what characteristics does a good high-side driver chip need to have? Typically, automotive applications are primarily evaluated from protection functions and load diagnostics in addition to normal switching and driving capabilities. Typical evaluation items are shown in Table 1.
Table 1 Typical evaluation items for high-side drivers
Is it a complete automotive grade high-side driver chip that realizes the above switch driving, functional protection and fault diagnosis functions?
The operating environment of automotive application systems is complex and harsh. To ensure long-term trouble-free operation of automotive chips, all emergency and extreme situations must be considered when designing the system. These include load dump, cold start, reverse battery polarity, short circuit to ground, loss of ground, loss of power, double battery crossover, spike clamping, and extreme operating temperatures. At the same time, automotive grade chips require longer service life. Most chips will have to work safely and reliably for more than 10 years as cars are launched. In addition, the fault tolerance rate requirements are also higher. For DPPM (defective products per million defects), consumer-grade chips are required to have no more than 500 defects, while automotive grade chips must be controlled to no more than 10 defects.
Before automotive devices are put into mass production, they often undergo a series of rigorous reliability tests to ensure that product reliability meets vehicle regulations.Currently, the automotive system certification standards commonly used in the industry include functional safety standard ISO 26262, quality management system certification IATF16949, reliability standard AEC-Q series certification, etc..Common vehicle system and chip EMC testing are shown in Table 2。
Table 2 Vehicle EMC tests and standards
It can be seen that in order to cope with the challenges of harsh environments in automotive applications, automotive-grade high-side driver chips must not only integrate many functions such as switch driving, functional protection and fault diagnosis, but also must comply with the above-mentioned various standard certifications. Therefore, a car-grade chip is stronger and more reliable than an industrial-grade or consumer-grade chip.
When making a car gauge chip, you must first take the car gauge into consideration
The high-side driver SGM42202Q/3Q series products launched by Shengbang Microelectronics have a wide voltage input range of 4.5V to 36V, a low on-resistance of 75mΩ, a maximum current limit of 22A, and can be configured with multi-level current limit steps (2.5 A/5A/10A/15A/22A), built-in overcurrent shielding time setting pin. The device is implemented using a single chip and is widely used in automotive BCM modules, ECU units and other systems.
SGM42203Q's low on-resistance and adjustable current-limiting gear characteristics can switch and drive a variety of resistive loads in automotive systems; the surge current protection time and steady-state current can be freely adjusted by changing the external capacitor and resistor constants. The characteristics of the current limit set value can be used in automotive systems to adjust the time from transient current to steady-state current to start capacitive loads such as car lights faster.
As shown in Figure 1 and Figure 2, the high-side driver integrates a 60V clamp circuit. Compared with the use of freewheeling diode clamp shutdown, the 60V clamp voltage greatly shortens the demagnetization turn-off time tDEMAG. In some applications such as injector drive, PWM control valve, etc., when there are strict requirements on the closing time, it can be easily handled; as shown in Figure 3 and Figure 4, when facing the 300mH inductive load drive shutdown, the measured The VCLAMP voltage is 60V and the turn-off demagnetization time tDEMAG is 9.2ms. According to the engineering approximate calculation formula (1), the demagnetization energy EAS can be calculated to be 276mJ. However, the actual turn-off measurement of SGM42203Q shows that the demagnetization energy EAS is 262.5mJ, which is similar to the theoretical value. This also provides a certain demagnetization dissipation capability when driving inductive loads. When driving loads whose turn-off dissipation energy is within the tolerance range of the high-side drive, there is no need to increase the cost of designing an external clamp.
Through the multi-function CS pin, SGM42203Q integrates diagnostic and current detection output functions. It can not only perform real-time current sampling during operation, but also output a VSENSEH high-level error in time when a fault is triggered, and notify the control unit.
Implementing basic protection functions is only the first step. Sunbond's requirements for automotive-grade high-side driver chips go far beyond that.
1: Automotive EMI/EMC test standard ISO7637-2
Because they often have to work under conditions such as high temperature and vibration, the environment of the automotive electrical system is very complex and harsh, and electrical system failures may often occur, such as alternator overvoltage, connection system disconnection, etc. In order to verify the impact of transient conduction interference along the power supply on the high-side driver, Sunbond tested the performance of the SGM42203Q in different combinations of no-load/load conditions when powered by 12V and 24V battery systems in accordance with the ISO 7637-2 standard. Figures 5 to 10 respectively show that when SGM42203Q simulates P1 negative pulse, P2a positive pulse, P3a negative pulse, P3b positive pulse, P4 reverse voltage and P5b load dump pulse, the high-side drive switching function behaves normally.
2: Evaluation of BCI large current injection interference
In actual application scenarios, the connecting cables of on-board parts with different functions of the car are generally bundled together, which will cause electromagnetic interference signals in different frequency bands to be coupled between different cables. In extreme cases, the interfered parts will fail.. Therefore, Saintbond adopts the BCI large current injection interference evaluation method when simulating the injection of RF signals into the power line or signal line of the product under test. According to the ISO 11452-4 standard, under 12V/24V battery power supply, the highest level 4, the tests are performed separately. The functional impact of common mode interference and differential mode interference injection at different distances (150mm, 450mm, 750mm) on the high-side drive with different loads is analyzed. Table 3 shows the BCI high current injection test conditions.
Table 3 High-side driver BCI high current injection test conditions
3: AEC-Q100-012 repeated short circuit times and SOA life test
Speaking of the harsh situations that are prone to high frequencies in automotive system applications, various short circuit events are unavoidable. Because cars use the metal structure of the car body as the entire ground plane, ground short circuits are more likely to occur. In accordance with the AEC-Q100-012 standard, SGM42203Q was subjected to various short-circuit tests under 12V power supply (as shown in Figure 11). According to the conditions shown in Table 4, high temperature (+125℃)/normal temperature (+25℃)/low temperature (-40℃), 12V/24V battery power supply, switch short circuit, PWM pulse repeated switch short circuit, and hot plug are completed. A series of tests including short circuit and repeated short circuit under long pulse (300ms) and short pulse (10ms).
Figure 11 High-side driver equivalent short circuit test circuit
Table 4 High-side driver equivalent short circuit test conditions
4: Testing in accordance with ZVEI general IC EMC IEC 61967-4 standard
Saintbond's high-side driver not only has basic driver protection functions, but also has passed the above-mentioned various EMC standard certifications and short-circuit tests under extreme applications to ensure device reliability. Next, we will refer to the IEC 61967-4 standard in the ZVEI general IC EMC test specification to measure the electromagnetic conducted emissions of the SGM42203Q. Referring to the IEC 62132-4 standard, the radio frequency power injection method is used to test the electromagnetic injection immunity of the high-side driver. Refer to the IEC 62215-3 standard to test the electromagnetic transient immunity of the high-side driver chip. In line with the principle of "to make a car-grade chip, you must first worry about the car grade". Each test in a harsh environment is to ensure the reliability, stability and safety of the car-grade high-side driver chip in automotive system applications. sex.
In addition to passing the above-mentioned strict vehicle standard tests, SGM42203Q also has other functional advantages (see Table 5 for details).
Table 5 SGM42202Q/3Q main advantages
High-side driver products have been around for nearly ten years, but still have high technical barriers. With the development of new energy vehicles and the demand for high reliability, intelligence and other features in automotive application design, high-side drive products also need to be constantly updated and iterated. How to judge their future application development trends is crucial to quickly occupy the potential market. . To this end, Shengbang Microelectronics has been working hard and we will launch more high-reliability high-side drive products that meet the needs of the future automotive market.
The following is the automotive grade drive product series recently provided by Shengbang. Welcome to call us for discussion!
Table 6 Shengbang High and Low Side Driver Product Roadmap
Table 7 Shengbang MOSFET driver product roadmap
 Stephane Fraisse. Smart High-Side Switches Application Note [EB/OL]. (2010-12-15). https://www.infineon.com/dgdl/Infineon-Application+Note-PROFET+12V-What+....
 Infineon Technologies AG. How to make good use of smart high-side switches [EB/OL]. https://zhuanlan.zhihu.com/p/315128197.
 How to obtain vehicle certification for domestic chips [EB/OL]. https://zhuanlan.zhihu.com/p/596491367.
 Automotive electronic product EMC testing project [EB/OL]. (2022-06-01). https://www.dongchedi.com/article/7104075416205394473.
 What is BCI high current injection [EB/OL]. (2023-01-29). https://baijiahao.baidu.com/s?id=1756347039125014944&wfr=spider&for=pc.
About Shengbang Microelectronics
Shengbang Microelectronics (Beijing) Co., Ltd. (stock code 300661) focuses on the research, development and sales of high-performance, high-quality analog integrated circuits. Products cover the two major fields of signal chain and power management, with more than 4,600 models available for sale in 30 categories, all independently developed and widely used in industrial, automotive electronics, communication equipment, consumer electronics, medical instruments and other fields, as well as the Internet of Things , new energy and artificial intelligence and other emerging markets.
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