A noise-canceling charge pump for area efficient PLL design

Phase noise of PLLs is one of the critical issues in high-performance transceivers. Especially, in-band noise is troublesome because the phase noise inside a loop bandwidth is hard to be filtered out due to low-pass characteristic of most PLL components. The in-band noise of PLLs is mainly caused by charge-pumps (CPs), so that large-size transistors are used to improve in-band noise of CPs. Due to this trade-off between inband noise and occupied area, a large area is needed for CPs in high-performance transceivers. In this paper, we propose a noise-canceling CP to improve in-band noise. The prototype of the proposed CP embedded in a 28-GHz LC-PLL was fabricated using 16nm FinFET process and 1.2-dB improvement of single sideband (SSB) integrated phase noise is achieved. As the results of in-band noise improvement, occupied area for the CP can be reduced to 22%.