A CMOS Current Interpolation DAC with Gamma Correction for LCD Source Driver
Date Issued
2010
Date
2010
Author(s)
Liu, Pang-Jung
Abstract
In recent years, applications of thin-film transistor (TFT) liquid crystal displays (LCDs) have rapidly increased due to their thin shape, light weight, and low cost. With the rapid evolution of LCD, a substantial demand develops LCD drivers with low power consumption, as well as high resolution and high speed. The source driver is especially critical for achieving high-quality display. The digital-to-analog converters (DACs) occupy more than 50% of the area of an 8-bit source driver area.
In order to reduce the DAC area, this thesis presents the design and implementation of a current interpolation DAC. The proposed DAC includes a cyclic DAC and current interpolation circuit. The signal processing aims to convert the digital input data into a linear analog voltage, and then change this voltage into a nonlinear voltage for gamma correction. The cyclic DAC performs linear D/A conversion, and the current interpolation circuit is used to transform the linear curve to nonlinear form by piecewise linear approximation. The benefit of using cyclic DACs is that only one bit of data needs to be stored for single-bit conversion. In a 10-bit source driver, for example, a 90% reduction in storages and level shifters is reflected. The current interpolation scheme is proposed for the LCD source driver to deal with the nonlinear requirement. In addition, the N-way-interleaved architecture is used to reduce the proposed DAC area further, and maintain optimum operation speed of cyclic DAC, circuit interpolation circuit, and output buffer. The proposed 10-bit DAC was successfully fabricated in TSMC 0.35-μm 5-V CMOS technology, and the core area is 0.215
Subjects
LCD driver
DAC
current interpolation and gamma correction
Type
thesis
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