Patent ID: 6806742
Filing Date: 2004-10-19
Classification: G01R,H03D,H03L

Abstract:
A method comprising:receiving first and second cyclic waveforms; generating a first control signal, wherein the de-assertion of the first control signal occurs at a specific point with respect to the first cyclic waveform; generating a second control signal, wherein the assertion of the second control signal occurs at a specific point with respect to the second cyclic waveform; charging a capacitor from a constant current source in response to de-assertion of a first control signal, wherein the current source comprises a source coupled between a first voltage rail and a first terminal of the capacitor and a sink coupled between a second voltage rail and a second terminal of the capacitor; isolating the capacitor from the first and second voltage rails in response to the assertion of a second control signal; and outputting the voltage across the capacitor after the assertion of the second control signal as a differential signal to indicate a phase relationship between the first and second cyclic waveforms.