The deal, which would allow Medtronic to be domiciled in Ireland, where Covidien is based, and thus take advantage of lower tax rates, could come as soon as Monday, one person said, asking not to be named because the matter is not public. Minneapolis-based Medtronic, the world’s largest stand-alone medical device maker, with an array of products ranging from heart defibrillators and stents to insulin pumps and spinal implants, has a market value of about $61 billion. Covidien, a maker of devices used in surgery, is valued at about $32 billion.