Design of a Smart Image Sensor with a Current Steering CMOS DAC for High Performance Autofocusing Micro-lens Driver

A smart image sensor system with a current-steering digital-to-analog converter (DAC) for autofocusing micro-lens driver is presented. Recently, most of smart image sensor systems want to extend the lens focusing distance with high speed motor drive. Thus they need a high-performance current-steering DAC to drive the lens focusing linear motor. In order to satisfy the specifications, DAC needs small chip area, low power consumption, and high speed operation. In this paper, a brick current cell layout technique and a novel digital logic are proposed. The measured results are within ±0.6LSB for INL, and within ±0.5LSB for DNL. Further, the measured SFDR is 79dB at 1.2MHz output frequency with 250MHz clock frequency. It has 45.6mW power dissipation at 3.3V power supply.