Resumo:
Modern Application Specific Integrated Circuits - ASICs are systems
frequently composed by mixed-signal blocks, consisting of analog and digital circuitry. The
analog blocks, in particular, need to be biased by voltage and current references, whose
accuracy certainly determine the maximum performance of the remaining blocks. One typical
block found in commercial ASICs is the Power Manangement, which can include DC/DC
converters (linear or switched) that provide regulated voltages for the remaining blocks. Yet,
there are ASIC blocks whose work at different voltages, so it is necessary a reference capable
to bias multiple voltages to Power Manangement block.
This work describes the design of 3 bits programmable, low drift, high PSRR
and high precision voltage reference, providing voltages from 0 to 2.1V, to be implemented in
a dedicated integrated circuit, which must present low sensibility to temperature and supply
variations. All design considerations, such as equations and modeling of error sources
(process variations of integrated transistors, resistors and capacitors) are made based on
TSMC CMOS 0.35µm technology. Also, it is presented the detailed design of each cell of the
reference, followed by their electrical simulations and layout of entire chip. Finally, in order
to validate the proposed reference, electrical simulations of a buck converter powering up a
DDR memory bank are conducted, from a 0.9V to 1.8V range.
