Automatic Adjustment of Phase Locked Loop Transfer Function

Masahiro YOSHIOKA  Nobuo FUJII  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E91-A   No.2   pp.483-490
Publication Date: 2008/02/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e91-a.2.483
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Analog Circuit Techniques and Related Topics)
phase locked loop,  gain adjustment,  frequency adjustment,  automatic calibration,  

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This paper presents an automatic adjustment of the transfer function of phase locked loop (PLL). The time constants and the gain factor of the transfer function are adjusted without opening the loop of PLL. The time constant adjustment is performed using a replica of the 1st order RC low pass filter and the gain factor is adjusted by detecting the open loop gain at the unity gain frequency. These adjustments are automatically carried out using a digitally controlled capacitance array and a digitally controlled charge pump. The proposed calibration can reduce the bandwidth error of 30% to 5% and the gain error of 7 dB to 1 dB.