Patent ID: 7209533

Claim:
An apparatus for preventing a DLL from locking into the harmonic phase and preventing a hang problem that is independent of temperature, voltage and process, comprising: a main loop including a first phase frequency detector (first PFD) coupled to a reference signal; a first charge pump coupled to the first PFD and coupled to a first node; a first filter coupled to the first node; a comparator having an input coupled to the first node and an output coupled to the first PFD; a voltage controlled delay line (VCDL) having an input coupled to the first node and an output coupled to the first PFD; a second loop, including a second phase frequency detector (second PFD) coupled to the reference signal; a second charge pump coupled to the second PFD and coupled to a second node; a second filter coupled to the second node; a buffer having an input coupled to the second node and an output coupled to the first PFD; and a voltage controlled oscillator (VCO) coupled to the first node, coupled to the second PFD.