Low-Overhead Self-Healing Methodology for Current Matching in Current-Steering DAC

Abstract

In this brief, a low-overhead self-healing method for current matching in current-steering digital-to-analog converters (CS-DACs) is demonstrated. In contrast to traditional calibration methods that adjust current values, a statistical element selection (SES) algorithm optimizes the selection of unary current cells via combinatorial redundancy. This SES-based self-healing method relaxes the matching requirements for the current source array and achieves high static linearity at a minimum overhead cost of one current comparator and one digital controller. Moreover, this proposed low-overhead method is fully compatible with other segmented CS-DAC designs. A 14-bit CS-DAC design with on-chip self-healing control loop was implemented in 130-nm CMOS technology to demonstrate the proposed approach. The core area of the prototype chip was measured as 0.9 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , with less than 0.1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> occupied by the current source array. After self-healing, the INLmax was measured as 0.64 least significant bit and spurious-free dynamic range was 85 dB for a 2-MHz input signal at 200-MS/s sampling rate.