Compared with industrial applications, the isolation requirements of automobiles are higher. Complex road conditions and noise during high-speed operation all cause great interference to the system. These all lead to stricter safety requirements for automotive applications. In actual use, Defects or reliability issues may result in costly product recalls and may even endanger the safety of drivers and occupants.
In order to meet the ever-increasing quality and reliability requirements, automotive system designers began to use digital isolators instead of optocouplers to provide safe isolation for hybrid vehicle (HEV) battery monitoring and power conversion applications. Unlike optocouplers, digital isolators are based on standard wafer CMOS semiconductor processes, which have a good reputation for use in automotive systems.
New energy vehicle bus distributed control strategy still uses the fuel vehicle mode, ECU centralized control, CAN bus node management, and no errors are allowed in this control system, because these are directly related to vehicle driving safety and whether each component is operating normally. In addition to using the CAN bus between nodes, the underlying data exchange between the MCU and the sensor uses the SPI bus, PWM, SENT, or analog signals, which need to be isolated to ensure accuracy and reliability.
When developing electric vehicle electronic circuits, digital isolators can be used to transfer digital signals between high-voltage battery packs and low-voltage control system electronic components. This solution is suitable for a variety of applications, such as high-voltage battery pack voltage monitoring, battery current measurement, Motor control, etc. Especially in battery management system (BMS) applications. For the selection of digital isolation devices, designers must consider several key performance parameters, including: device power consumption, PCB space limitations, data rate/data consistency (channel-to-channel matching), and appropriate isolation and operating voltage (in the entire car Life cycle).
L There is a big difference between the digital isolator and the optocoupler for the required operating current of the isolation device. Assuming that a 1MHz SPI interface is used for battery monitoring applications, for the four digital isolation channels required by the SPI communication bus, Zhongke Geli Micro's ME1041 has a digital isolation like the ME1041 compared to the traditional optocoupler solution. The device has significant advantages in operating power consumption.
L In BMS development, PCB area is a precious asset, and designers must build a solution that can be applied to ultra-compact areas. The spacing requirements for high-voltage to low-voltage interfaces (commonly known as creepage distances and clearances) are defined by various electrical standards, and components must meet the minimum requirements that these standards specify for a given application. The two isolation solutions of digital and optocoupler are compared to determine which solution can save a lot of space for the PCB board.
For digital isolation solutions, the ME1041 is available in a 16-lead SOIC-W package with a standard package size of 10.3mm x 10.3mm and a total component area of 106 mm2. The equivalent optocoupler solution requires four 5-lead SOIC packaged devices with a standard JEDEC package size of 7.0 mm x 3.6 mm and a unit area of 25.2 mm2. Four components need to be placed on the PCB board, and the distance between the devices is generally 1.2 mm. Adding the total PCB area required for the optocoupler solution, the designer must leave 134.5 mm2 of space. Obviously, with a digital isolator solution, designers can already save about 28 mm2.
After limiting the area of the isolation device, the designer next needs to consider the supporting components needed for the entire solution. Digital isolators (such as ME1041) only need to use two external bypass capacitors. Assuming a 0603 package capacitor, the occupied area is 2.5 mm2. For a typical optocoupler solution, the designer must add four resistors (5.1mm2), four capacitors (5.1mm2), and four precursor circuits (33mm2) because most microcontrollers cannot handle 10 of their GPIO pins mA power requirements. At this point, the designer can see that the digital isolator has obvious advantages when the PCB area needs to be considered.
Another design consideration related to the PCB space is the driving problem of the high-voltage side of the isolation device. For BMS applications, the power consumption needs to be balanced on the battery monitoring device to prevent internal imbalances in the battery pack.
For optocoupler solutions, a separate DC-DC converter is required to provide an isolated operating voltage to drive the high-voltage side interface, which will further increase the area requirements of the PCB. In digital isolation devices, designers can choose a digital isolator with integrated isolation power supply, which contains an SPI interface isolation channel, and also integrates a DC-DC converter function for driving high-voltage side interfaces. The package size is the same as the ME1041 digital isolator, which does not increase the area requirements of the PCB board.
Compared with optocoupler solutions, Grid Micro's digital isolators allow designers to create isolation circuits with lower cost, smaller size, higher performance, lower power consumption and more reliable. This isolation technology has an extensive product portfolio, a proven track record of industrial innovation, and a strong commitment to superior engineering design to meet your isolation needs at any time.