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Automobile wiper system solutions
   In the present, the distal end of the dual wiper system, so the synchronization between the mechanical connection of the wiper to achieve (Figure 1). This approach is necessary because the position of the windshield wipers or on dirt, the wind will make the different left and right wiper action. Over the years, the automobile industry has been looking for an effective noise reduction and reduced mechanical connection spatial intelligence solutions.
   A scheme is to use the electronic system to replace the mechanical connection (Figure 2). In this architecture, each wiper driven by a DC motor. DC motors can be directly installed by the internal components of the motor controller and driver IC micro to control. An interface processing with synchronization of the wiper so, there is no need for a mechanical connection between a conventional wiper wiper system, thereby significantly reducing noise and saving space.
   Due to cost reasons, the use of a wiper system is a DC motor. Support and four power MOSFET PWM to control the direction of full H-bridge driver gate driver is able to control these motors. For such applications the high-voltage IC must be designed to process, and must be suitable for use in harsh environments. Furthermore, the windshield wiper systems, such as large capacity must be used to optimize DC application communication interface.
   Since the electronic apparatus of the wiper from the car radio equipment is usually very close, therefore, must be controlled to EMC radiation, causes a car radio to car driver interrupt electrical unbearable. You can use differential serial communication interface (SCI) transceiver to reduce such radiation, improve EMC performance. SCI transceiver is a differential device, the only one wiper system which can work in single-ended mode. SCI gate drive features make it very similar to LIN devices. However, compared with the standard LIN interfaces, faster data transfer rates it up to 100k baud.
   Each wiper module (Figure 3) consists of a microcontroller, a highly integrated gate driver and the DC components. A plurality of Hall sensors measure both the position of the wipers. Wiper drive via a command transmitted to the microcontroller switches. The electronic device may be mounted close to the wiper motor, eliminating the need for a lot of space.
   The importance of low current consumption ECU is increasingly prominent. To ensure inactive IC quiescent current is very low, requires the use of a dedicated wake and sleep modes. Typical functional division wiper applications, as shown by the microcontroller, the microcontroller supply voltage regulator and other discrete elements (such as Hall sensors) consisting of 4. For safety reasons, you need to add a watchdog in the system, this is because when driving in the rain, the wipers damage may be dangerous.
   To further prevent system failure, IC used cars need to have many features, such as thermal shutdown, overvoltage and undervoltage protection, and full protection against short circuits, but also to meet stringent vehicle certification requirements (anti conducted interference, EMC and ESD protection ). In order to solve these problems and meet the above functional requirements, Atmel has developed a highly integrated gate driver IC ATA6026. The gate driver IC comprises a voltage regulator 5V/100mA with a watchdog, thereby reducing the required PCB area smaller number of external components required to compact design, which is very critical in the electromechanical system. The IC can achieve motion control, and thus this functionality without any additional memory in the microcontroller. Windows watchdog window open during the conversion to high from low triggered by the microcontroller via WD pin. If the watchdog detects an error window that is not triggered when you open the window when the window is closed or an error is triggered, it will generate a reset pulse.
   Figure 5 shows a block diagram of the realization of the function and schematic diagram of a typical application. Microcontroller via a speed signal and a PWM signal to control the direction of the driver IC of the function. Since the gate of the external chip must drive the H-bridge, it uses two push-pull driver is used to control the drive of the two external high power NMOS FET, two push-pull driver is used to control the low-end drives two external power NMOS FET. Drive can be used with standard or logic level power NMOS FET. High-end control drive to an external bootstrap capacitor provides the gate voltage higher than the battery voltage of 8V ~ 14V. Reverse motor control can also be achieved. By using a charge pump to a high power gate drive, in both directions are possible to achieve a 100% duty cycle. To prevent the emergence peak current H-bridge, the use of non-overlapping phases achieve switching external power NMOS transistor. Cross-conduction time is defined by the combination of an external RC circuit.
   Low power and on-chip low dropout voltage regulator is used for both internal and external voltage source. As an external power transistor components help reduce power consumption. In the inactive state, the sleep mode of the device to ensure very low quiescent current (typically 35 microamps). For 6 ~ 9V battery voltage is concerned, the adjusted output voltage is 5V ± 10%; When the battery voltage exceeds 9V , the regulated output voltage of 5V ± 3%. To prevent damage to the external NPN transistor and IC, a sense resistor can be used to detect the voltage regulator output current. If the over-current, the voltage regulator may limit the current to a specific value. This means that if the function of the voltage regulator to change the function of the current regulator, the output voltage will drop to a very low value. If there is a permanent conduction state (100% PWM, the bootstrap function is not available), fully integrated charge pump can still drive the gate of an external power supply for the high-power MOSFET. In addition, the external power NMOS used for reverse battery protected by the gate charge pump output power.
As mentioned earlier, ECU applications need to have the Sleep features to meet the requirements of low current consumption. In the ATA6026's sleep mode, or data can be used to wake EN pin IC. Only a few modules is awake (band gap with external DC blocking capacitor 100nF internal 5V voltage regulator for input structure detection threshold and the EN pin wake SCI receiver module section). Power-on default mode is activated. To achieve the transition between the two modes, you can take three steps. In addition to activation / deactivation EN pin addition, there is also a wake-up function to achieve through the use of SCI transceiver second method. In sleep mode, SCI transceiver is part of the active and working in single-ended mode. If SCI achieve activation, the EN pin can remain low without affecting the active mode.
   As the voltage regulator, motion control, watchdog, and communication interfaces are integrated on a small QFN package single chip, total system costs have been reduced, while in almost all without adaptation motor drive applications, the output stages are maintaining the flexibility plug and play. Are part of a motion control IC, only the speed signal PWM and direction information to be provided by the microcontroller. Two diagnostic pin can achieve fail-safe function.





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