| D/A converter is an important interface circuit for digital signal to analog signal in the system which includes both digital part and analog part.It is widely used in communication,audio,industrial control,medical instrument and so on,he has made great contributions to life,military affairs and national defense.Among all kinds of D/A converters,R-2R resistance ladder structure D/A converter has the advantages of good matching,high precision,small area and good monotonicity.Based on TSMC 0.25?m BCD process,a high precision D/A converter with 16 bit resolution is studied and designed in this paper.Its Power Supply Voltage±15V,external reference Voltage±5V,is used for high-voltage equipment,and can realize single-pole(0?5V)and double-pole(±10V)output voltage range conversion,it mainly consists of reference current source bias circuit,high precision R-2R resistor switch array,high gain Class AB output amplifier and digital calibration circuit.The 16-bit D/A converter adopts a segmented voltage mode R-2R resistor ladder network+thermometer code main structure.After improving the traditional R-2R resistor switch array,it adopts 6+6+4 segments to reduce the difficulty of switch matching,greatly reduced the chip area.The D/A converter with resistance can not achieve 16-bit conversion precision,so an improved digital calibration technique is designed in this paper,which greatly improves the linearity of the output voltage of D/A converter.The reference current bias circuit with low drift and high power supply rejection can provide stable and high precision bias for the whole system analog circuit,and the output op amp with high gain and wide output swing,in order to avoid the influence of the mismatch of the on-resistance of MOS switches on the output voltage of R-2R resistive switch array,the output voltage of R-2R resistive switch array is amplified and the linearity of the analog output of operational amplifier is improved,the switch voltage control circuit is designed,which can realize the high precision of R-2R resistor switch array.The layout of the key modules of D/A converter is matched with the layout of the resistance switch array,which improves the precision of the analog output of the whole system.Based on the designed D/A converter,the whole performance index of the D/A converter is simulated and verified by using the virtuoso software spectre simulator of cadence company.The simulation results show that the conversion rate is 24.5V/?s,the setup time is 5.01?s,the total power consumption is 82.6m W and the total chip layout area is3.2×1.8mm~2in the temperature range of-55°C?+125°C,the range of post-simulation DNL and INL are±0.8LSB and±1.2LSB respectively.Performance is superior to similar high-voltage application chip products,can be very good to achieve a high-precision digital signal to analog signal conversion. |
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