Patent ID: 7088193

Claim:
A fast starting on-chip crystal oscillation circuit comprises: a V DD integrated circuit (IC) pad; a V SS IC pad; first crystal IC pad for coupling to a first node of an external crystal oscillator; second crystal IC pad for coupling to a second node of the external crystal oscillator; a first transistor having a gate, a drain, and a source, wherein the drain of the first transistor is operably coupled to the V DD IC pad and wherein the gate of the first transistor is operably coupled to receive a crystal enable signal; a second transistor having a gate, a drain, and a source, wherein the source of the second transistor is operably coupled to the V SS IC pad and wherein the gate of the second transistor is operably coupled to the source of the first transistor; a third transistor having a gate, a drain, and a source, wherein the gate of the third transistor is operably coupled to the drain of the second transistor and wherein the drain of the third transistor is operably coupled to the V DD IC pad; an inverter having an input, an output, a power source connection, and a power return connection, wherein the input of the inverter is operably coupled to the first crystal IC pad, wherein the output of the inverter is operably coupled to the second crystal IC pad, wherein the power source connection is operably coupled to the source of the third transistor and wherein the power return connection is operably coupled to the V SS IC pad; a resistor operably coupled to the input and the output of the inverter; a first capacitor operably coupled to the input of the inverter; and a second capacitor operably coupled to the output of the inverter.