Negative N-epi biasing sensing and high side gate driver output spurious turn-on prevention due to N-epi P-sub diode conduction during N-epi negative transient voltage

1. A high-side driver in a driver circuit for driving a half-bridge stage having high- and low-side power switching devices series connected at a switched node, the high-side driver driving the high-side power switching device, the high-side driver comprising:

first and second complementary switched MOSFET series connected at a high-side node, driving the high-side power switching device, one of the MOSFETs having a parasitic bipolar transistor formed between the substrate, an N+ epitaxial region connected to the high-side driver supply voltage, and the switched node, with the parasitic transistor having a base electrode formed by the N+ epitaxial region, an emitter electrode formed by the substrate and a collector electrode formed by the switched node, such that if a transient voltage that is negative with respect to the substrate is present at the high-side driver supply voltage, said parasitic transistor will conduct a short circuit current between the switched node and the substrate;

a first circuit for controlling the conduction of the first and second MOSFETs to switch said high-side switching device ON and OFF;

a diffusion in said N+ epitaxial region in which a terminal connected to the switched node is provided by the diffusion forming the collector of the parasitic transistor; and

a second circuit coupled to the diffusion for sensing the high-side driver supply voltage at the epitaxial region and providing a signal to said first circuit to prevent turn-ON of the high-side power switching device.

2. The high-side driver of claim 1 , wherein the second circuit comprises a sensor connected to sense voltage between the switched node and the diffusion when said parasitic transistor begins to conduct due to a negative transient at said high-side supply voltage.

3. The high-side driver of claim 2 , wherein the second circuit further comprises:

a transistor switch coupled to said sensor;

a blanking circuit to prevent turning ON of the transistor for duration of a preset blanking time; and

a reset counter for providing a reset pulse to reset the first circuit while the negative voltage is sensed and the transistor is ON, resetting of the first circuit keeping the high-side power switching device turned OFF.

4. The high-side driver of claim 2 , wherein the sensor comprise a resistor.

5. The high-side driver of claim 1 , wherein the diffusion comprises a ring in said epitaxial region.

6. The high-side driver of claim 1 , wherein one of the MOSFETs is an N MOS device and the parasitic transistor comprises a parasitic PNP transistor.