| Digital-to-analog converter(DAC)is an important interface device for connecting digital systems and analog systems.With the rapid development of wireless communication,the conversion rate of DACs is getting higher and higher.The performance of high-speed DACs restricts the signal processing speed of the entire communication transceiver system.Therefore,research and design of high-speed and high-precision DAC chips have important practical and practical significance.Based on the 110 nm CMOS(Complementary Metal Oxide Semiconductor)process,this paper designs a two-way 12-bit high-speed digital-to-analog converter with current rudder,which mainly accomplishes the following work and innovation:(1)The working principle of digital-to-analog converter is studied.On the basis of analyzing the performance and shortcomings of various structure DAC circuits and design indicators,the "6+6" segmented current rudder structure is determined as the DAC circuit structure of this design.The lower six digit input code uses binary decoding and the upper six bits are decoded using a thermometer.(2)The DAC analog module is mainly used to provide a stable and accurate current source,mainly including a bandgap reference voltage source,a voltage follower,a voltage-current conversion circuit,a current source,and a current source switching signal circuit.The bandgap reference voltage source adopts the PTAT structure,and the startup circuit is added to prevent the whole circuit from operating at the zero point state;the voltage follower adopts the secondary operational amplifier structure,and the Miller compensation circuit is added to avoid the working pole and increase the phase margin;voltage-current The conversion circuit is a two-stage operational amplifier connected to a negative feedback to form a closed loop to achieve voltage-current conversion;the current source uses a cascode structure to improve the output impedance;the current source switching signal circuit passes the output voltage of the bandgap reference voltage source.The resistor is divided to obtain the required voltage,and then the voltage follower provides the gate voltage for the current source switch to ensure that the switch is in saturation.(3)The digital module is mainly used to control the switching of the current source,andmainly includes a circuit such as a channel selection circuit,a buffer circuit,a segmentation decoding circuit,a synchronous latch,and a clipping low cross circuit.The channel selection circuit uses a MOS transistor as a switch to select whether to provide a bias voltage for the current source;the buffer circuit uses a master-slave flip-flop composed of a NOT gate and a transfer gate to implement timing control of the input digital signal;The high 6-bit binary input is decoded into the thermometer.The logic algebra is used to reduce the use of the logic gate type,and the same logic gate sharing is realized,so that the delay time of the high 6-bit decoding calculation is as equal as possible,reducing the generation of glitch;The memory is a loop composed of two inverters,and the input data is latched in the loop;the limiting low cross circuit stretches the low level to the required voltage to ensure that the differential current source switch cannot be simultaneously Disconnected and the switch operates in the saturation zone when closed.(4)The digital-to-analog converter designed in this paper was simulated in Spectre,and the layout of the circuit was completed in the layout editor.The design rules and consistency verification were carried out using Calibre and Assura software.The simulation results show that the dual 12-bit segmented current steering digital-to-analog converter loads 150? resistors at a clock frequency of 160 MHz.Under normal operation of each module,DNL(differential nonlinearity)is ±0.75 LSB,INL(integration nonThe linearity is ± 1.1LSB.When the signal frequency is 10 MHz,the SFDR(no spurious dynamic range)reaches-72 dB,which meets the design requirements and can be applied to the vehicle voice control system. |
PDF Full Text Request