VDD-independent oscillator insensitive to process variation

摘要

A method of providing an oscillating signal, comprising providing a first constant current flowing from a positive power supply node, the first constant current independent of a variation in a positive power supply node voltage, providing a second constant current flowing from a positive power supply node to a second electrode of a capacitor, a first electrode of the capacitor connected directly to the positive power supply node, the second constant current mirroring the first constant current and charging the capacitor by reducing a voltage across the capacitor. A third constant current is provided flowing from the positive power supply node through a first NMOS transistor and mirroring the first constant current, the first NMOS transistor having a gate connected directly to the second electrode of the capacitor and an oscillating signal generated by turning on the first NMOS transistor when the capacitor reaches a predetermined voltage level.

主权项

1. A method, comprising:
providing a first constant current flowing from a positive power supply node, the first constant current independent of a variation in a positive power supply node voltage; providing a second constant current flowing from a positive power supply node and independent of variations in the positive power supply node voltage, the second constant current flowing to a second electrode of a capacitor, a first electrode of the capacitor connected directly to the positive power supply node, the second constant current mirroring the first constant current and charging the capacitor by reducing a voltage across the capacitor; providing a third constant current flowing from the positive power supply node through a first NMOS transistor and mirroring the first constant current, the first NMOS transistor having a gate connected directly to the second electrode of the capacitor; and generating an oscillating signal with a period independent of variations in the positive power supply node voltage by turning on the first NMOS transistor when the capacitor reaches a predetermined and constant voltage level.