A very-high output impedance charge pump for low-voltage low-power PLLs

✍ Scribed by L.-F. Tanguay; M. Sawan; Y. Savaria

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 328 KB
• Volume: 40
• Category: Article
• ISSN: 0026-2692
• DOI: 10.1016/j.mejo.2009.03.001

✦ Synopsis

This article presents the design of a high output compliance, very-high output impedance single-ended charge pump implemented using a new low-voltage current mirror. The output current is sampled and a feedback loop forces it to be equal to the desired reference current. This results in a very-high output impedance over a very wide output voltage range, accurate Up/Down current matching, and low transient glitches. The proposed charge pump was implemented using STMicroelectronics 1-V 90-nm CMOS process. Simulations using Spectre show that the Up/Down output currents remain constant and matched within 1% over a charge pump output voltage ranging from 119 to 873 mV. Monte Carlo process variations and mismatch simulations indicate that the 1 À s standard deviation between the Up and Down current components is 1:4 mA, or 6.8% of the nominal 20 mA charge pump current at either end of the output voltage range.