The 21-year-old has made one substitute appearance for the Tractor Boys this campaign but has not featured under Mick McCarthy.
He is expected to go straight into John Sheridan's side as the Pilgrims face Morecambe this season.
And it was Sheridan's presence that led McCarthy to agree to the deal.
"Ronan is going there and he's going to go and play some games," McCarthy told the club's official website.
"John Sheridan is somebody I know personally and he plays the game in the right way.
"He likes to play football and I think Ronan will enjoy it."