Frequency synthesizer for on-chip testing and automated tuning

This paper presents a compact, phase-locked loop (PLL) based, frequency synthesizer suitable for built-in testing and automatic tuning applications operating in the 100 MHz frequency range. Key features of this design include a differential charge pump with common mode feedback (CMFB) and a voltage controlled oscillator (VCO) based on a pseudo-differential OTA with a linear transconductance control and tuning invariant output resistance. Experimental results from an integrated prototype fabricated using standard 0.35 /spl mu/m CMOS technology are presented. The measured HD3 of the output signal is better than -39 dB over 80% of the tuning range: 40-160 MHz. The circuit occupies a silicon area of 200/spl times/1000 /spl mu/m/sup 2/ and operates from a 3.3 V power supply.