Phase‐interpolator‐based glitch‐free fractional frequency divider with track‐and‐hold technique

Abstract

This Letter presents an 8-bit fractional frequency divider by utilising current-mode phase interpolator (PI) for digital phase-locked loops. A novel track-and-hold circuitry is proposed between the PI and divide-by-2. It can remove the glitches generated by the current-interpolation structure. This method also relaxes the requirement of the minimum input frequency, while maintaining the same output frequency. The proposed fractional frequency divider is designed and fabricated with a 65-nm CMOS technology. It dissipates a DC power of 0.8 mW from a 1.2 V supply. The measurement result shows that the fractional frequency divider achieves an uncalibrated in-band spur of -43 dBc.