System For The Tcxo 12 Successive Approximation Adc Design And Simulation

The main task in this paper is to design the analog-to-digital (ADC) converter in the temperature-compensated crystal oscillator system, which is used to convert the temperature into digital data. Considering that the temperature would not change dramatically, we adopt the successive approximation (SAR) analog-to-digital converter. It has moderate-speed, high-resolution and low power dissipation after the contrast of various ADC structure.Designed and fabricated in TSMC 0.35μm 5V CMOS technology, the SAR ADC is designed to be 12 bits and 1MSPS with the input range of 1.5V under the power supply of 5V. And it contains 3 main modules.The 12-bit segmented capacitive digital-to-analog converter (DAC) module is designed with a 5-bit arrays and a 7-bit arrays, and the value of the capacitors are carefully planned. The design of the sample and hold circuit is very important. Here the bottom plate technique is employed to cancel the charge injection error, and the 7-bit arrays is used as sample and hold capacitors.The high-resolution analog comparator module is designed, in which a multi-stage structure consisting of three pre-amplifiers, a latch and a digital flip-flop circuit is adopted. It used an offset cancellation technique to cancel offset, used a cascode circuit to reduce kickback noise, and used a digital flip-flop circuit to make a high performance digital output.The digital module is designed to coordinates analog circuits to finish the successive approximation. And the generation of the digital control signal used a 16-bit counter using GRAY code.The Hspice simulation results show that every module behaves well and the performance of the ADC meets the requirement.