a constant-transconductance (gm) reference generator circuit receiving a power supply voltage, wherein the constant-gm reference generator circuit comprises a first current mirror to provide a first reference voltage and a second current mirror to provide a second reference voltage;

a power detection circuit coupled to the first current mirror to receive the first reference voltage, wherein the power detection circuit is coupled to the second current mirror to receive the second reference voltage, wherein the power detection circuit is operated to receive the power supply voltage, wherein the power detection circuit is operated to provide an output voltage having one of two logic states at least based on the second reference voltage and the power supply voltage; and

a second power detection circuit, wherein the constant-gm reference generator circuit further comprises a third current mirror, wherein the second power detection circuit is coupled to the first current mirror to receive the first reference voltage, wherein the second power detection circuit is coupled to the third current mirror to receive a third reference voltage, wherein the second power detection circuit receives a second power supply voltage, wherein the second power detection circuit provides a second output voltage having one of two logic states at least based on third reference voltage and the second power supply voltage.