A Low Power Rc Time Constant Auto-Tuning Circuit For Rc-Integrators In High Linearity Continuous-Time Delta Sigma Modulators

This paper presents the design of a low power RC time constant tuning circuit for high linearity 5th order continuous time Delta Sigma modulator used in LTE-A application with 40MHz bandwidth. This auto-tuning system contains an analog integrator, a voltage comparator, and a digital tuning engine performed by a clock generator, a register and a counter which generate a control word that sets a programmable capacitors bank to obtain an RC time constant accuracy better than +/- 2%. It resolves process variations issues which could result in up to +/- 30% of RC time constant uncertainty and degrade the Delta Sigma modulators SNDR. The system has been designed in a 65nm CMOS technology with 1.2 V supply voltage and power consumption is less than 200 mu W.