On-chip RC measurement and calibration circuit using Wheatstone bridge

In this paper an on-chip RC measurement and calibration circuit using a Wheatstone bridge is presented. In the bridge the resistor R is compared with the virtual resistor of a switched capacitor network. By using a Wheatstone bridge as the measurement principle no accurate timing signals or accurate reference voltages are necessary. The realized system tunes the RC product within 1.5% of the nominal value. The 5 bits digital output of the circuit is used to reduce the spread of critical parameters of analog signal processing blocks like filters, ADCs and DACs. The prototype circuit is part of a large audio and multi-mode baseband test chip for mobile phones. The chip was processed in TSMC´s 65 nm CMOS technology and uses both 2.5V and 1.2V supply voltages. The chip area of the RC measurement and calibration circuit is 0.03 mm . Measurement results are given to show the viability of the proposed circuit.