access icon free Reference spur suppression technique using ratioed current charge pump

© The Institution of Engineering and Technology
Received 25/03/2013, Published

Reference spurs are one of the main problems in integer-N phase-locked loops (PLLs). A ratioed current charge pump is proposed to suppress reference spur magnitude in the PLL output. The ratioed current charge pump can be implemented by resizing the source and drain network of the charge pump. A formula to calculate the ratioed current and transistor size is presented. The reference spur magnitude for a PLL with a ratioed current charge pump is compared to a conventional charge pump PLL, resulting in about 4 dBc/Hz improvement in the reference spur magnitude.

Inspec keywords: transistors; charge pump circuits; phase locked loops

Other keywords: ratioed current charge pump; charge pump drain network; reference spur magnitude; transistor size; reference spur suppression technique; integer-N phase-locked loops; integer-N PLL; PLL output

Subjects: Modulators, demodulators, discriminators and mixers; Power electronics, supply and supervisory circuits

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