US 7,321,649 B2
Phase locked loop with improved phase lock/unlock detection function
Jae-hoon Lee, Suwon (Korea, Republic of)
Assigned to Samsung Electronics Co., Ltd., Suwon-si (Korea, Republic of)
Filed on Dec. 29, 2003, as Appl. No. 10/747,486.
Claims priority of application No. 10-2003-0007158 (KR), filed on Feb. 05, 2003.
Prior Publication US 2004/0150480 A1, Aug. 05, 2004
Int. Cl. H03D 3/24 (2006.01)
U.S. Cl. 375—376  [327/156; 331/1 A] 16 Claims
OG exemplary drawing
 
1. A phase locked loop (PLL) which generates a clock pulse signal at a frequency from a synchronization signal of a cathode ray tube (CRT) monitor, the PLL comprising:
a phase frequency detector (PFD) which compares a phase and frequency of the synchronization signal to that of a reference signal, and outputs an up signal or a down signal;
a charge pump which outputs a pumping current in response to the up or down signal;
a loop filter which outputs a control voltage according to the pumping current;
a voltage controlled oscillator (VCO) which outputs a clock pulse signal having a frequency determined by the control voltage;
a divider which divides the clock pulse signal by a division ratio and outputs the reference signal;
a phase unlock detection circuit which detects an initial phase unlock from the up or down signal for outputting a first detection signal, and outputs a first internal control signal according to the up or down signal;
a phase lock/unlock detection circuit which outputs a second detection signal in response to the first internal control signal and the first detection signal; and
an output circuit which performs a logic operation on the first detection signal and the second detection signal, and outputs a third detection signal.