Abstract:
A high performance internally compensated Low Drop Out (LDO) regulator has been
presented in this thesis which is stable with any value and type of output capacitor.
Normally any type of regulator consisting negative feedback loop requires an output
capacitor to collapse the loop bandwidth so that other internal poles in the loop do not
have much effect in the stability. Again depending on the type, the equivalent series
resistance (ESR) of the capacitor can vary a wide range like 10mn to Ion which
inherently produces a zero in the system and makes the stability requirements more
complex and challenging. Normally most of the regulators are designed to be stable
either with high ESR or with low ESR but not with both. The novelty of the LDO
regulator proposed in this thesis is its system architecture which makes it stable with
ESR value of the output capacitor as low as 10mn to as high as Ion which gives the
user to choose any type of capacitor in output and even with the absence of output
capacitor itself which can save the very valuable space in the application board. This
LDO regulator is desigued in a pseudo BiCMOS process which includes few more
layers like deep N-Well, P-welliayers with the vanilla CMOS process and hence has
much lower cost than BiCMOS process. Along with the output capacitor and ESR
independent improved stability, the other remarkable features of this proposed LDO
regulator are ultra low line regulation, very low drop out voltage, high power supply
rejection ration (PSRR), short circuit current limit, over temperature sensing and
thermal shutdown, no shut down leakage current, under voltage lock out (UVLO)
mode, low operating current, ultra low output voltage drift with temperature, quick
start up time and low operating noise etc. Simulation results are presented in this
thesis to support all these claims. The full layout of this proposed regulator has been
implemented in 0.5!U Utechnology and the implementation issues and challenges with
applied methods to overcome those in this particular layout are also discussed in this
thesis.
