Patent ID: 6924709
Filing Date: 2005-08-02
Classification: H03K

Abstract:
1. An oscillator with improved sensitivity to component variation due to process shift, comprising: a first comparator circuit and a second comparator circuit; a charging-discharging circuit coupled to a first input of the first comparator circuit and to a first input of the second comparator circuit; a resistor string coupled to a second input of the first comparator circuit and to a second input of the second comparator circuit; a latch configured to combine an output of the first comparator circuit and an output of the second comparator circuit; wherein the resistor string is operable to maintain a first reference voltage at the second input of the first comparator circuit and a second reference voltage at the second input of the second comparator circuit; wherein the first reference voltage is substantially higher than the second reference voltage; wherein an output of the latch is coupled to the charging-discharging circuit, forming a feedback loop; wherein the output of the first comparator circuit is operable to change states when the first input of the first comparator circuit reaches a voltage level substantially commensurate with the first reference voltage; wherein the output of the second comparator circuit is operable to change states when the first input of the second comparator circuit reaches a voltage level substantially commensurate with the second reference voltage; wherein the charging-discharging circuit is operable to charge the first input of the first comparator circuit and the first input of the second comparator circuit to a voltage level substantially commensurate with the first reference voltage; wherein the charging-discharging circuit is operable to discharge the first input of the first comparator circuit and the first input of the second comparator circuit to a voltage level substantially commensurate with the second reference voltage; and wherein the resistor string comprises at least two different structure types.