设计了一个基于金属氧化物薄膜晶体管工艺的8位电流舵数/模转换器(Digital to Analog Converter,DAC),包括定时刷新模块、同步寄存器电路、分段译码电路、开关驱动电路、开关阵列和电流源阵列、多路选择器网络、随机序列发生器。在数字电路中设计定时刷新结构解决了传统的自举逻辑门电荷泄露导致的电流源开关驱动电压的下降,避免了在低频信号下采样出错问题的发生。提出采用差分对偶译码的结构,保证打开和关闭两路信号可以同时到达开关驱动电路,保证驱动电路中电压上升和下降窗口的对称性,减小输出的毛刺;同时利用数字电路中的D触发器和译码电路中的逻辑门实现驱动增强电路,保证可以驱动模拟电路中的高位单位电流源,提高转换速率;利用动态元件匹配(Dynamic Elements Matching,DEM)技术提高DAC的动态性能。后仿真结果表明,所设计的DAC面积为73 mm²,功耗为6.5 mW,输出电流摆幅为301.46 μA,最大转换速率为32 kS/s,在单位电流源的随机匹配误差的标准差为0.1的条件下,奈奎斯特频率下的无杂散动态范围(Spurious-Free Dynamic Range,SFDR)可达到42.43 dB,最大的微分非线性(Differential Nonlinearity,DNL)为0.36 LSB,最大的积分非线性(Integral Nonlinearity,INL)为1.75 LSB,满足生物医学用柔性电子系统的需求。

In this paper, an 8-bit current-steering Digital to Analog Converter(DAC) based on Metal Oxide Thin Film Transistor (MO-TFT) technology is designed, which includes a timing refresh module, a synchronous register circuit, a segmented decoding circuit, a switch driver circuit, a switch array and a current source array, a multiplexer network, and a random sequence generator. The timing refresh structure is designed in the digital circuit to solve the traditional bootstrap logic gate charge leakage caused by the current source switch driving voltage drop, to avoid the problem of sampling errors in low frequency signals. A differential dual decoding structure is proposed, so that the open and close signals could reach the switch driver circuit at the same time, ensuring the symmetry of the voltage rise and fall Windows in the driver circuit and reduced the output glitter. Meanwhile, the D flip-flop in the digital circuit and the logic gate in the decoder circuit are used to implement the driver enhancement circuit, guaranteeing the high bit unit current source in the analog circuit can be driven and the conversion rate is improved. Dynamic Elements Matching (DEM) technique is employed to improve the dynamic performance of DAC. The poster-simulation results show that the designed DAC has an area of 73 mm², a power consumption of 6.5 mW, an output current swing of 301.46 μA, a maximum conversion rate of 32 kS/s. Under the condition that the standard deviation of the random matching error of the unit current source is 0.1, the Spurious-Free Dynamic Range (SFDR) at the Nyquist frequency can reach 42.43 dB, the maximum Differential Nonlinearity (DNL) is 0.36 LSB, and the maximum Integral Nonlinearity (INL) is 1.75 LSB, meeting the requirements of flexible electronic systems for biomedical applications.