Romanian Journal of Information Science and Technology (ROMJIST)

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ROMJIST is a publication of Romanian Academy,
Section for Information Science and Technology

Editor – in – Chief:
Academician Dan Dascalu

Secretariate (office):
Adriana Neagu
Adress for correspondence: romjist@romjist.ro

Editing of the printed version: Mihaela Marian (Publishing House of the Romanian Academy, Bucharest)

Sponsor: National Institute
for R & D in Microtechnology
(IMT Bucharest)

ROMJIST Volume 21, No. 1, 2018, pp. 3-17, Paper no. 577/2018
 

R. Groza, I. A. Potarniche, B. S. Kirei, M. D. Topa
Digitally controlled oscillator for all-digital frequency locked loops

ABSTRACT: A digitally controlled oscillator is presented as a suitable solution for all-digital frequency lock loops. The system consists of a bias circuit, current-voltage converters and a current controlled oscillator, which is implemented using log-domain circuits. In this way, the oscillation frequency can be tuned using the bias currents. The bias circuit consists of a binary decoder and a current division network. The role of the decoder is to control the output current values of the division network via a 10-bit digital control word. Thus, it was possible to obtain 1024 distinct bias current values which yielded 1024 frequency values. The current-voltage converter transforms the output current into a voltage necessary for the next stage. All circuits were implemented using Virtuoso Analog Design Environment from Cadence using a 180nm CMOS technology. The MOS transistors for the log-domain blocks are working in sub-threshold region. Spectre simulations were performed to demonstrate de functionality of the proposed circuit.

KEYWORDS: DCO, ADFLL, ELIN, sub-threshold, log-domain

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