Research And Design Of High Precision BiCMOS Reference For Pipelined A/D Converter

As a key part of pipelined A/D converter, reference not only provides the bias voltage for the system, but also plays the part of the compared voltage in the sub-ADC. Its performances are important to the pipelined A/D converter system, so the reference design becomes significant.Based on SMIC 0.35um BiCMOS process, we propose a 0.5V high- precision voltage reference. The proposed voltage reference is composed of a positive temperature coefficient current module, a negative temperature coefficient current module and a resistor divider network. The positive temperature coefficient current module uses an advanced sub-threshold OP-AMP to control the offset voltage less than 44uV. The negative temperature coefficient current module uses low-voltage cascode current mirror to improve the accuracy of the output current. Using Cadence Spectre simulator and BSIM3V3 models for SMIC 0.35um BiCMOS process, the whole voltage reference circuit was simulated. The simulation result shows that the voltage reference has a TC of 21ppm/℃over the temperature range of -60℃~80℃, and a power line regulation(PLR) of 8.7ppm/V for a supply voltage of 3.0 to 3.6V. In the frequency range of 1Hz~16KHz, the PSRR is -66.5dB, at the frequency point of 16MHz, PSRR reach the minimum of -34.6dB. Besides, the set up time is less than 10us.From the simulation results, its performance achieve the requirements of pipelined A/D convertor system, so the proposed voltage reference has a high application value.Finally, according to the mixed-signal system layout strategy, the layout of the key module is designed with SMIC 0.35um 2P3M mixed-signal BiCMOS process.