中小屏幕TFT-LCD驱动芯片的输出缓冲电路

Output Buffer Circuits for Medium or Small Size TFT-LCD Driver IC

在分析中小屏幕TFT-LCD驱动芯片的负荷特性的基础上,提出了一种新型的驱动电压输出缓冲电路结构.通过负反馈动态控制输出级的工作状态,具有交替提供拉电流和灌电流的驱动能力,可有效抑制输出电压的波动.与传统的两级运算放大器电路相比,该电路结构简单,稳定性能好,降低了静态功耗并节省了芯片面积.采用0·25μmCMOS工艺设计并实现了两种不同输出电压的缓冲电路.HSPICE仿真结果表明,输出电压缓冲电路的静态电流为3μA,Offset电压小于±2mV.同时,当TFT-LCD的驱动电压在-8^+16V之间切换时,输出电压的波动范围小于±0·4V,输出电压的恢复时间小于7μs.经对工程样片的测试知,其性能完全满足中小屏幕TFT-LCD驱动控制芯片的要求.

Based on the detailed analysis of the loading properties of a medium or small size TFT-LCD driver IC,a novel output buffer circuit of driving voltages is proposed. By using negative voltage feedback, the operating states of the output stage in the output buffer circuit can be controlled dynamically,which can provide source current and sink current alternately,so that the output voltage fluctuations can be rejected effectively. Compared with a conventional push-pull output buffer circuit, it has such advantages as lower static power consumption, smaller chip area, and better stability. Two output buffer circuits driving different voltages are designed and implemented using a 0.25μm CMOS process. HSPICE simulation results show that the static current is 3μA and the offset voltage is less than ＋ 2mV. Furthermore,when the driving voltage for the TFT-LCD panel is switched between - 8 and 16V,the fluctuations and the recovering times of the output voltages are less than ± 0.4V and 7μs,respectively. By measuring the TFT-LCD driver IC＇s engineering samples,it is shown that the proposed output buffer circuits can completely satisfy the demands of a medium or small size TFT-LCD driver IC.