On-chip current sensing

• Main Authors: LUEBBE JUERGEN, TAN WENXIAO
• Format: Patent
• Language: English
• Published: 19.04.2011
• Subjects: CONTROLLING; PHYSICS; REGULATING; SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES

One embodiment of the invention includes an on-chip current-sense system for measuring a magnitude of an output current through a power transistor. The system includes a first sense transistor that conducts a first reference current to or from a phase node and a second sense transistor configured to conduct a second reference current to or from a power rail. The first and second sense transistors can be substantially identical and can be proportionally matched to the power transistor. An OTA receives the first and second reference currents and a third reference current that flows to or from the phase node and generates a sense current that is proportional to the output current in response to the first, second, and third reference currents. A sense circuit compares the sense current with a predetermined magnitude and generates an over-current signal in response to the sense current being greater than the predetermined magnitude to indicate an over-current condition of the output current.