480 MHz 10-tap Clock Generator Using Edge-Combiner DLL for USB 2.0 Applications

Abstract EN

A clock generator with an edge-combiner DLL (ECDLL) has been developed for USB 2.0 applications.

The clock generator generates 480 MHz 10-tap output signals from a 12 MHz reference signal and consists of three DLLs to shrink the design area so that it is smaller than a conventional one based on a PLL.

Each DLL is applied to our proposed shot pulse reset technique to prevent from a harmonic lock and is applied to a voltage-controlled delay line (VCDL) with a trimming function to operate against any process voltage temperature (PVT) variations.

A 90 nm CMOS process was used to fabricate our proposed clock generator.

The 480 MHz 10-tap output signals satisfy the USB 2.0 specifications.

A power consumption is less than 1.3 mW and a locking time is less than 3.5 μs, which are far less than a conventional one, 10.0 μs.

The design area is 200×225 μm, which is half that of the conventional one.