Research And Design Of High Speed And High Precision DAC Based On Heterogeneous Integration

The digital-to-analog converter undertakes the task of converting from digital signals to analog signals.It is an indispensable interface circuit between analog circuits and digital circuits.High-speed and high-precision digital-to-analog converters are in wide demand such as 5G communications,waveform generators,digital processing units,and radar systems.It is difficult for traditional digital-to-analog converters based on CMOS technology to balance high speed and high precision.Heterogeneous integration provides a solution for improving the accuracy of high-speed digital-to-analog converters.This paper firstly introduces the development history of heterogeneous integrated digital-analog hybrid circuits and high-speed and high-precision digital-to-analog converters,then learn design experience from them.Die-to-Die micro-assembly heterogeneous integration scheme is used in this paper.The overall circuit frame structure of 2-GSps,14-bit digital-to-analog converter based on 0.7μm InP DHBT and Huahong Grace’s 0.18μm SiGe BiCMOS is proposed in this paper.In order to meet the accuracy requirements under high-speed data input,the current source in the traditional CMOS digital-to-analog converter is replaced with a SiGe HBT current source.Due to the high current density of the HBT current source,the method of 6+8 segment decoding and the R-2R resistance weighting network suitable for the low 8-bit current source are designed to compromise the performance and power consumption of the circuit.Considering the potential mismatch of the HBT current source,a DEM decoding circuit for high 6-bit decoding is designed in this paper to improve the harmonic distortion caused by the mismatch of the current source.The widely used LVDS data interface circuit is used to receive external input signals,and the current transmission characteristics of LVDS can effectively reduce electromagnetic interference.In order to ensure the high-frequency dynamic performance of the digital-to-analog converter,a deglitch circuit based on high-speed sample-and-hold is designed in this paper,which can resample the output waveform at the stable point.The electromagnetic model of the heterogeneous interconnection via is introduced,and the heterogeneous interconnection buffer circuit for signal transmission is designed in this paper.In this paper,the Cadence Virtuoso IC61 platform is used to complete the schematic and layout design of the overall circuit.The post-simulation results show that the spurious-free dynamic range of the designed DAC in the first Nyquist frequency domain is greater than 75 d Bc,and its DNL and INL are respectively 1.4 LSB and 1.2 LSB.Under the mixed power supply of 1.8 V,3.3V and 5 V,the average power of the whole circuit is 1.09 W.The total area of the DAC layout is2.2 mm~2.