The smart power high-side switch: description of a specific technology, its basic devices, and monitoring circuitries

The choice of a processing technology and of a design methodology for the realization of a monolithic, solid-state, high-side power switch for automotive applications is discussed. The technology is basically MOS on a high-resistance epilayer and therefore does not contain built-in junction isolation walls. Instead, it is shown that convenient isolation, both static and dynamic, is achieved by a floating-well concept. The floating well, if conveniently protected by a peripheral attenuator circuit, decouples the well voltage from voltage fluctuations in the epilayer that result from turning on and off the VDMOS device, thereby isolating the logic section of the device from the power section. The floating-well technique lends itself to producing isolated capacitors, Zener devices, and a controlled vertical bipolar transistor, which prove to be useful in producing a reliable, low-consumption, fast-switching smart power high-side switch. The technology appears to be suited to handle particularly high current values