Electronic control units have an essential role in driving improvements in automotive comfort, safety and environmental compatibility. They are also establishing themselves in new application fields, among them assistive, entertainment and networking functions.
Power transistors with integrated safety and diagnostic functions have been in use since the 1980s as a replacement for mechanical relays, and their use has been growing ever since. They can be deployed in practically any electrical consumer or automotive actuator applications.
Since its launch, the VIPower range of products from STMicroelectronics has undergone several stages of technological progression, during which the sizes of the silicon structures have been reduced. This has not only enabled ever more powerful output transistors and more compact housings, but also increases and refinements in safety mechanisms and diagnostic functions.
STMicroelectronics now offers a range of high-side driver products, based on the current VIPower M0-7 technology, which was developed and certified to meet automotive requirements. Consequently, these drivers offer innovative functions and improvements, among them low standby currents and optimised emission handling.
Structure of a VIPower power switch
The key design feature of VIPower products are the vertical power transistors combined with planar analogue and logic structures, either as a monolithic IC or as a hybrid solution with two or three chips. Output currents of up to 100A are conducted to the pins via aluminium or copper bond wires. PowerSSO or DPAK-esque variants such as HPAK or Octapak are used as housings. To discharge the heat generated by power dissipation, they have heatsink tabs in the base of the housing, on which the chips are soldered. Where smaller currents are used or power dissipation is kept low, low-cost SO and SOT plastic housings are used.
Scalability and flexibility
The VIPower M0-7 range of high-side drivers has a suitable switch for most electrical systems in the automobile, covering the spectrum of needs to control resistive, capacitive and inductive loads. With its extensive pin compatibility – not only for drivers with an identical number of outputs, but also for pin-compatible single and dual drivers in a compact PowerSSO-16 housing – it offers scalability and flexibility. The space requirement by the PowerSSO-16 is similar to that of an SO-8 housing, which corresponds to a reduction of 50 to 75% compared to the preceding technology.
Fig. 1: Pin compatibility between single and dual drivers in a PowerSSO-16 housing
MultiSense diagnostics
The analogue current measurement of the M0-7 high-side driver, or Current Sense, enables precise measurement of the load current within a wide current range, down to small currents of 10mA. The primary benefit of Current Sense is the ability to monitor the connected load(s) and detect load cut-offs. Overloads, caused by short circuits in the output or a triggering of the integrated power or current limiter to protect the driver itself, are signaled by a digital flag on the MultiSense pin of the driver. In this case, the high-side driver switches from an analogue power source to a voltage level of 5.5V (VsenseH signal), enabling the MCU to diagnose the driver overload and deactivate the driver.
In addition to Current Sense, the M0-7 high-side drivers also offer other diagnostic options, namely measurements of the local power supply (Vcc Sense) and the chip temperature (Tchip Sense). This is achieved by providing these Sense signals on the same Sense pin, which is why it was called the MultiSense pin. The desired signal (CS, Vcc Sense or Tchip Sense) can be selected by the MCU using the Sense multiplexer integrated into the driver. A Sense-Enable pin activates the diagnostic functions or switches the entire Sense block to Hi-Z to reduce power consumption
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