Abstract: A voltage regulator includes a linear mode regulator having a high pass filter circuit connected between its output and an output node, and a switch mode regulator having an low pass filter circuit connected between its output and the same output node. The high pass filter passes high frequency AC current provided by the linear mode regulator to the output node and reduces the low frequency AC and DC currents to substantially zero, and the low pass filter prevents the high frequency AC current produced by the linear mode regulator from being drawn by the switch mode regulator and passes the low AC and DC currents provided by the switch mode regulator to the output node. Thus, the present regulator offers the high response speed and low noise of a linear mode regulator, and the high power efficiency and large continuous output current capability of a switch mode regulator.

Abstract: A failure detection scheme for switching voltage regulators senses a parameter which normally transitions above and below a predetermined threshold during each clock cycle. A decision circuit tracks the sensed parameter, and toggles an output when the sensed parameter transitions normally. A counter counts clock cycles, and toggles its output when a predetermined number is reached. The counter also has a reset input which receives the output of the decision circuit, and is reset to an initial value when the decision circuit output toggles. If the sensed parameter fails to transition normally, the reset input is not toggled and the count value increments with each clock cycle. If the failure persists for the predetermined number of clock cycles, the counter output toggles to indicate a failure, enabling the failed regulator to be repaired or replaced before additional failures occur.