Techniques for a 6-bit Digital Data Driver Using the Alternating Voltage Driving Method

Abstract

An alternating voltage driving method (AVDM) for gray scale drive technology is proposed that utilizes the low-pass filter characteristics of the TFT-LCD to eliminate periodical components from alternating voltage and applies DC voltage which is represented as an average value to a pixel. This paper describes the structure of the AVDM six-bit driver and the logical design techniques used to create its output circuit, which is a voltage interpolating circuit. From evaluation of the low-pass filter effect, it is proved that most of the effect is produced by the time constant of the TFT and the pixel itself. It is confirmed that voltage deviations due to the line resistances in the driver die are a principal cause of the output deviations along with the low-pass filter effect. Design criteria for the voltage deviations are described. Last, the multiple AVDM is proposed for non-linear interpolation. A logical combinational method is described for applying it to a six-bit driver that needs 5 gray scale voltages.