Charge pump with reduced current mismatch for reference spur minimization in PLLs

In this article, a charge pump circuit featuring minimal mismatch between its up and down currents is proposed. In conventional charge pumps, where error amplifiers are used in feedback, the factor that hinders exact current matching is the offset voltage of the error amplifier. In the proposed desi...

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Bibliographic Details
Published in:Analog integrated circuits and signal processing 2018-05, Vol.95 (2), p.209-221
Main Authors: Biswas, Debdut, Bhattacharyya, Tarun Kanti
Format: Article
Language:English
Subjects:
Amplifier design
Amplifiers
Charge pumps
Circuits
Circuits and Systems
Components industry
Computer simulation
Electric potential
Electrical Engineering
Engineering
Errors
Input output
Signal,Image and Speech Processing
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Summary:In this article, a charge pump circuit featuring minimal mismatch between its up and down currents is proposed. In conventional charge pumps, where error amplifiers are used in feedback, the factor that hinders exact current matching is the offset voltage of the error amplifier. In the proposed design, the input offset voltage is computed and additional current delivering/comsuming branch is implemented to supplement for the error current. The new charge pump requires a few error amplifiers and a dynamic comparator for its operation. Simulations considering process variations show current mismatch of less than 20 nA even at the worst case event. The proposed charge pump has been utilized in PLL circuits to reduce reference spurs and simulations of these PLLs show remarkable spur reduction.
ISSN:0925-1030
1573-1979
DOI:10.1007/s10470-018-1163-z