US Patent 7456671 Hierarchical scalable high resolution digital programmable delay circuit

A hierarchical and modular clock programmable delay circuit structure is described that can achieve almost unlimited fine resolution and unlimited delay range. The same circuit may also be applied to critical circuits that require fine adjustment in timing applications. The modular design allows the circuit and its layout to be synthesized by software to achieve desired delay resolution and range. Constant capacitive load of internal node enhances the linearity of achieved delay by digital controls.