Charge pump with perfect current matching characteristics in phase-locked loops

Author

Lee, Jae-shin ; Keel, Min-Sun ; Lim, Shin-II ; Kim, Suki

Author_Institution

Dept. of Electron. Eng., Korea Univ., Seoul, South Korea

Volume

36

Issue

23

fYear

2000

fDate

11/9/2000 12:00:00 AM

Firstpage

1907

Lastpage

1908

Abstract

Conventional CMOS charge pump circuits have some current mismatching characteristics. The current mismatch of the charge pump in the PLLs generates a phase offset, which increases spurs in the PLL output signals. In particular, it reduces the locking range in wide range PLLs with a dual loop scheme. A new charge pump circuit with perfect current matching characteristics is proposed. By using an error amplifier and reference current sources, one can achieve a charge pump with good current matching characteristics. It shows nearly perfect current matching characteristics over the whole VCO input range, and the amount of the reference spur is <-75 dBc in the PLL output signal. The charge pump circuit is implemented in a 0.25 μm CMOS process

Keywords

CMOS analogue integrated circuits; integrated circuit design; phase locked loops; voltage-controlled oscillators; 0.25 micron; CMOS; VCO input range; charge pump; dual loop scheme; error amplifier; locking range; output signal; perfect current matching characteristics; phase offset; phase-locked loops; reference current sources; spurs;

fLanguage

English

Journal_Title

Electronics Letters

Publisher

iet

ISSN

0013-5194

Type

jour

DOI

10.1049/el:20001358

Filename

888639