Patent ID: 7382203
Filing Date: 2008-06-03
Classification: H03K,H03L

Abstract:
1. A delay circuit, which is included in a ring oscillator, the ring oscillator produces an oscillating signal, the delay circuit comprising: a current source for providing a current; a first circuit coupled to the current source for receiving an input signal and producing an output signal; a second circuit coupled to the current source and the first circuit; a first adjustable impedance element coupled to the first circuit; a second adjustable impedance element coupled to the second circuit; and a control circuit coupled to the first adjustable impedance element and the second adjustable impedance element for producing a first control signal to control a first resistance of the first adjustable impedance element and producing a second control signal to control a second resistance of the second adjustable impedance element; wherein the first control signal produced by the control circuit includes a digital coarse-tuning element and an analog fine-tuning element coupled in parallel for controlling the first resistance, the second control signal produced by the control circuit includes a digital coarse-tuning element and an analog fine-tuning element coupled in parallel for controlling the second resistance.