3 papers relating to LDO soft-start circuit.
Hope it helps
(1) 2009_A Compact Ramp-Based Soft-Start Circuit for voltage Regulator_TCAS-II 2009
(2) 2010_A Compact Fully-Integrated Extremum-Selector-Based Soft-Start Circuit for Voltage Regulator_TCAS-II 2010
(3) 2010_A Current-Limiter-Based Soft-Start Scheme for Linear and Low-Dropout Voltage Regulators_ISCAS2010