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Power windows: now much more than just a motor and switch
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Power windows: now much more than just a motor and switch
As with most improvements, there are both expected and unanticipated ripple effects in product objectives, associated design, and actual production. As cars became increasingly “electrified” with more motors, switches, lighting, power seats, infotainment, advanced driver assistance systems (ADAS), mandated safety features, and more, one of the logical places to start rewiring was the car door and its windows.Get more news about power window switch supplier,you can vist our website!
Fortunately, the migration to using low-speed networks such as the Controller Area Network (CAN bus) or Local Interconnect Network (LIN Bus) within the car has reduced the cable-harness difficulty. Now, 12-V power needs to go only to the regulator motor in the door, while a networked switch with thinner cabling can signal the motor controller to raise/lower/stop the window and monitor performance.
Though what started out as a basic network-friendly window-motor controller soon evolved into a smart, processor-based controller with advanced performance capabilities. The enhanced window network interface/motor controller IC needs more-sophisticated power management and regulation, and that’s where a power-management IC (PMIC) is needed. The DC power for sophisticated motor-related IC needs to be monitored and managed, and it needs a self-test to ensure that any excessive variations of power or other problems are detected promptly, and appropriate action is taken immediately before there is any damage to the motor or associated components.
ICs such as the MAX16137 from Maxim Integrated Products (now part of Analog Devices) directly address this need. This low-voltage, highly accurate supervisory circuit monitors a single system-supply voltage rail for undervoltage and overvoltage fault, specifically targeting the needs of automobile power windows and their interface/controller ICs, although it can be used for similar monitoring elsewhere in the vehicle (Figure 1).
When the monitored supply voltage drops below the undervoltage threshold or goes above the overvoltage threshold, the IC’s reset output goes low; this output returns to “normal” after a reset timeout period when the supply voltage returns to within the undervoltage and overvoltage threshold window. The 1% accuracy provides supervisory consistency, while the overvoltage/undervoltage windowing value can be factory set at ±4 percent to ±11 percent of target voltage.That’s just one role of the MAX16137. In addition, its Built-In-Self-Test (BIST) diagnostic capability monitors the health of the internal reset circuit during power-up. If that built-in self-test fails, the MAX16137 pulls its BIST output low to alert the associated processor.
As space in car doors is at a premium, the MAX16137 coming in an 8-lead, 2 × 2 mm package is an attractive fit. The advanced diagnostics at the chip level help developers meet system-level functional safety requirements with significantly reduced board-space requirements.
As the complexity of the door innards and other “peripheral” functions increases, implementing all the functions becomes an increasing problem. Managing and delivering controlled power for the various motors and mechanisms which are used for the complicated door system and adjuncts — and it is truly a system — is a substantial design challenge.
One solution is available via the STMicroelectronics L99DZ200G automotive front-door device with LIN and CAN interfaces. This IC enables a single-chip “front-drives-rear” arrangement for managing a front-door window, mirror, and lighting as well as the rear-window lift. It does this with lower quiescent current, greater reliability, faster assembly, reduced bill of materials, and shorter development time than multichip or discrete components.