DESIGN OF A LOW NOISE, LOW POWER AND SPURIOUS FREE PHASE FREQUENCY DETECTOR AND CHARGE PUMP FOR PHASE-LOCKED LOOPS

Abstract

This paper presents a very simple approach to design effective PFD (Phase Frequency Detector) and charge pump (CP) circuits for high frequency Phase-Locked Loop (PLL) applications. The PFD design uses only six transistors for the detection process, which reduces the chip area and power consumption of the PLL block.  It also minimizes the dead zone and eliminates the reset path to reduce the delay.  The output is passed through a buffer to suppress the distortion and to reduce the overall output noise. Phase noise has been reduced to -156 (dBc/Hz) at 1 MHz offset frequency. A simple current mirror based charge pump circuit is presented next. The charge pump design incorporates the use of transmission gates and transistors as capacitors to reduce switching error and clock feed through. The proposed design has a symmetric structure in terms of W/L ratios, transistor positioning and number of transistors in both up and down network which produces a stable charging operation and reduces the spurious jumps in the output voltage.  The overall output noise including thermal and flicker noise of the complete design at high frequencies is as low as -213 db at 4GHz. The proposed design provides a high output voltage swing of 1.4V while operating at 1.5V supply voltage. The design has been implemented in 1P-9M UMC 90nm CMOS technology. Simulations show the effectiveness of the design in terms of lower power consumption, lower noise and reduced distortion.