OFFSET, DELAY AND PARASITICALLY IMMUNE RESISTER-CAPACITOR (RC) TRACKING LOOP AND METHOD OF USING SAME

摘要

A resistor capacitor (RC) tracking loop includes a parasitic insensitive integrator ( 211 ) charged by a buffer ( 207 ) with offset compensation. The integrator ( 211 ) operates to provide an accurate ramped voltage proportional to a measured RC time constant. A single comparator ( 213 ) is used for sensing the voltage ramp rate by detecting two multiplexed reference voltages (V_REFLO V_REFHI). A timer within controller ( 201 ) is triggered by the V_REFLO crossing at comparator ( 213 ). The timer counts the number of precision reference clock periods (F_REF) that occur between the V_REFLO and V_REFHI crossings and adjusts an accumulator within controller ( 201 ) to a value (M). This value (M) is directly used to adjust a resistor and/or capacitor array used in a continuous time filter whose bandwidth and corner frequency can be precisely tuned.