Power integrated circuit having reverse-voltage protection

摘要

In power integrated circuits having both control circuit components and at least one power device, the circuit components are typically isolated from the power device by placing them in separate "wells" of opposite conductivity type to that of the underlying substrate. However, when these power integrated circuits are used in applications (such as automotive electronics) where supply voltage can be inadvertently reversed, large and potentially damaging currents can flow through the circuit components. In order to prevent such large reverse currents from flowing, an additional p-n junction is incorporated within the circuit "well", thus preventing undesirably large reverse current flow. However, introduction of this addition p-n junction creates a vertical transistor within the device, thus creating another potentially damaging current path and also creating potential reverse breakdown voltage problems. In order to alleviate these problems, a reverse voltage protection circuit employing two series-connected MOS switching transistors is used to shunt current away from the base of the vertical transistor. Additionally, the effectiveness of this reverse voltage protection circuit can be improved by the addition of an integrated bias circuit that serves to generate a gate bias voltage that further enhances the breakdown characteristics of the circuit.