Method and apparatus for generating a power-on reset with an adjustable falling edge for power management

摘要

A method and apparatus is directed to a power-on reset circuit for providing a power-on reset signal having a rising edge and an adjustable falling edge. A reference generator circuit produces two different reference signals in response to a power supply signal. The two reference signals are compared by a comparison circuit to produce a resulting reference signal. The resulting reference signal tracks the power supply signal until a first threshold potential is reached. When the first threshold potential is reached, a rising edge is produced in the power-on reset signal. The rising edge indicates that the power supply signal has reached an operating potential. A second threshold potential corresponds to the adjustable falling edge of the power-on reset signal. When the power supply signal decreases below the second threshold potential, the adjustable falling edge is produced in the power-on reset signal. The second threshold potential is adjusted when an adjustment circuit selectively couples additional transistors to the reference generator circuit. The additional transistors change the level of the second threshold potential in relation to the power supply signal. Adjusting the second threshold potential adjusts the falling edge of the power-on reset signal. The falling edge may operate as a low voltage detector by indicating that the power supply signal has decreased below its operating potential.