I am using PL3150 controller IC whose Vmin=4.75.and has active low RESET
My reset controller IC has a maximum threshold of 4.64V and typical value of 4.55V
according to this specification when the power supply is building the micro-controller will not be active before 4.75V, but the reset signal will be deasserted once the supply voltage exceeds a value of 4.64V, so whether this gap will have some negative effect or my selection of reset controller IC fine.
For a circuit that's operating reliable by design you should use a different reset controller.
Do you have any indications, that the micro-controller will not be active before 4.75V. That's very unlikely unless the controller has an internal supply voltage monitor. In this case, the external reset controller won't be needed at all. Otherwise, the controller can be expected to operate at a much lower voltage, but possibly unreliablelly.