A 1.2 – 6.4 GHz clock generator with a low-power DCO and programmable multiplier in 40-nm CMOS

This paper presents a clock generator for a MIPI M-PHY serial link transmitter, which includes an ADPLL, a digitally controlled oscillator (DCO), a programmable multiplier, and the actual serial driver. The paper focuses on the design of a DCO and how to enhance the frequency resolution to diminish the quantization noise introduced by the frequency discretization. As a result, a 17-kHz DCO frequency tuning resolution is demonstrated. Furthermore, implementation details of a low-power programmable 1-to-2-or-4 frequency multiplier are elaborated. The design has been implemented in a 40-nm CMOS process. The measurement results verify that the circuit provides the MIPI clock data rates from 1.248 GHz to 5.83 GHz. The DCO and multiplier unit dissipates a maximum of 3.9 mW from a 1.1 V supply and covers a small die area of 0.012 mm².