I have a design：power supply input is 12V，and output is -4.75V，load current is 30A.
Does LTM4650A support this inverting application?
LTM4650A can be used for inverting output applications. However, please be reminded that the input voltage is rated up to 16V only. In your case, the input voltage seen by the module will be 12+4.75=16.75V which is slightly beyond the maximum voltage rating.