Switched Capacitor Based Bandgap-Reference
Temperature independent references are important building blocks in analog and mixed-signal integrated circuit design. The classical Band Gap-Reference combines the negative VBE temperature coefficient of a bipolar transistor with the voltage drop over a resistor driven by a posititive to absolute temperature (PTAT) current to result in a temperature independent voltage of about 1.2V. Such a voltage is not compliant with modern CMOS processes that have supply voltages below 1V. Engineers have therefore seeked for alternative ways to generate a supply independent voltage around vdd/2 for modern CMOS processes.
One possibility is to use switched capacitor technique to both generate and constant current as well as to build a summing network for the generation of the constant band-gap voltage . Switched capacitor networks have the advantage that they can be made to have linear input/output characteristics that are also proportional to the operating frequency. Their drawback is that they create an intrinsic voltage ripple that has to be heavily suppressed in the case of a reference.
This thesis aims at the design of a switched capacitor based band-gap reference of 600mV in a 130nm CMOS technology with a defined noise budget and the task to minimize the power consumption and to stay within a defined layout area. The thesis offers the possibility to study main aspects of analog and mixed-signal design, such as noise, linearity, matching, small signal-concepts and power consumption and also to do a layout.
- Analog Integrated Circuits (AIC)
- 20% Theory
- 50% Design
- 30% Implementation
Detailed Task Description
- A. Shrivastava, et. al., "A 32nW Bandgap Reference Voltage Operational from 0.5V Supply for Ultra-Low Power Systems", ISSCC 2015