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The automotive sector is one of the most challenging areas for semiconductor manufacturers; customers demand very high quality and reliability at rock-bottom prices, while the huge volumes that can result from a successful design-in attract competitors from all over the world. To succeed in this sector, semiconductor manufacturers need to continually invest in new technologies and product development. This is true for the most sophisticated end of the automotive market such as engine control, car multimedia and for functions such as lamp drivers, where features such as protection and diagnostics must be cost-effectively integrated.  What do we mean by cost-effective? Clearly, the product itself must be competitively priced but cost-effectiveness involves much more than the component price and can only be measured in terms of the total impact it makes on the system cost. For example, it is now common for high side drivers to include diagnostic facilities - either by means of a logic signal or by making the output of an integrated current sensing circuit available to the external microcontroller. The second is the more flexible solution; by comparing the sensed current with the expected values, the microcontroller can detect abnormal operation due to short circuits, open circuits or other kinds of load failure. Although many microcontrollers incorporate A-D converters and analog I/O lines, the number of digital I/O pins usually greatly exceeds the number of analog lines. When a number of different loads have to be controlled - for example, signal indicators and various interior lights in a car - there can easily be a shortage of analogue I/O pins. The latest multichannel high side driver from ST eliminates this problem by incorporating a quad analog multiplexer in the device. Housed in a compact PowerSO-16 surface mounting package, the VNQ05XSP16 is a quad driver, with each output capable of driving a load higher than 10W. State-of-the-art features include a multiplexed proportional load current sense output, undervoltage and overvoltage shutdown and overvoltage clamping, built-in current limitation and thermal shutdown, reverse battery protection and protection against loss of ground or Vcc. The VNQ05XSP16 may well be almost indestructible but lamps and other loads are not, which is why the built-in analog multiplexer is a major benefit. As shown in Figure 1, each of the four channels incorporates a current sensing circuit that produces a current proportional to the load current. The external microcontroller can select any one sense current to be sent to the output pin by sending the appropriate logic signals to the two Select pins.  Figure 1  Figure 2 Figure 2 shows the operation of the Select pins. There is also a Sense Enable input that can be used to enable and disable the diagnostic function; if the Sense Enable pin is at a low logic level, the Current Sense pin presents a high impedance and therefore gives no information to the microcontroller. This is particularly useful if more than one high side driver is being used i.e. if there are more than four loads to be controlled. Figure 3 shows that a pair of VNQ05XSP16 devices can be used to drive up to eight loads, with the microcontroller able to monitor the output current through any of the loads, despite using only one sense resistor and one analog I/O port.  Figure 3 The VNQ05XSP16 is built with the latest ST proprietary VIPower M0-3 technology, the same technology that is used in ST’s popular OMNIFET and High Side Driver families (almost indestructible protected power MOSFETs in LSD and HSD configuration). VIPower M0-3 is a vertical smart power technology that allows a rugged power MOSFET to be combined with on-chip analog and digital circuitry. The vertical structure of the output power stage enables very high current densities to be achieved and the devices feature unrivalled ruggedness and energy handling capability, thanks to active clamping of the gate-drain voltage to below the avalanche threshold  |
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