I. Introduction
Low-Side drivers (Fig. 1) as well as high-side (Fig. 2) are used to switch electrical loads with a power transistor (LDMOS). Today a wide variety of different configurations are available. There are integrated high-side and low-side drivers but also solutions with external power transistors or external protection circuitry. A high-side driver with external components has the advantage that their substrate is isolated from the driving circuit, allowing negative voltages at certain nodes and therefore a faster switch-off than in integrated solutions. However, an integrated solution is often preferred due to cost and reliability reasons. for some applications, like an H-bridge driver, both high-side and low-side drivers are needed. in other applications just one of the two possibilities is chosen. Although high-side drivers provide some protection against overvoltage, with inductive loads negative voltages can appear and need to be handled by the circuit. for low-side drivers the protection is well known, no negative voltages are seen and therefore integrated low-side drivers can switch off inductivities faster than integrated high-side drivers. in this paper, an integrated configurable high-side/low-side driver is introduced [3], shown in Fig. 3. the basic principles of both configurations were combined to develop this configurable driver, which can be configured as LSD or HSD by external wiring only, providing high flexibility for various applications. Both configurations consist of three basic components: the load, the switching transistor and a driving circuit. Furthermore, in the majority of cases protection circuitry is needed. in previous solutions [1], [2], HSD and LSD could not be interchanged mainly because of their dedicated clamping structures which limit the voltages when switching inductive loads. Furthermore, the switching of an integrated HSD has been confined by the voltage clamping of the substrate diode. This also caused a rather slow switching behavior. This limit has been overcome in the driver presented here by a protection circuit using modified Zener diodes with improved isolation. A further challenge for a combined HSD/LSD is to keep this protection functional for both configurations. This is also facilitated by the modified, substrate-isolated Zener diodes. the paper will present the basic driver concept, the diode design, and experimental results demonstrating the intended clamping behavior as well as fast and symmetric switching behavior.
Low-side driver application.
High-side driver application.
Concept of the configurable HSD/LSD.