How to include the ramp up time of step input in the RC circuit design?

[electrowhiz]

Hi All,

I wished to design the RC circuit with a delay of 5ms to reach 5V. In actual case, if the 5V is supplied by the DC-DC converter, it will not be step input i.e DC-DC converter will take some time to reach the 5V. Suppose it takes 0.2ms (assumption) as a ramp up time to reach the 5V, how to include the effect of ramp up voltage in this equation Vc=V(1-e^(-t/RC)

Thanks