Model for St. Peter's
This is a drawing by Michelangelo detailing the reconstruction of St. Peter's basilica, originally built by Constantine in 323 A.D.
Notice that Michelangelo implemented an ovoid shaped dome and it is slightly, but definitely larger that Brunelleschi's, with a height of 448 feet.
Michelangelo used Brunelleschi's dome as a starting point, you can see that the dome for St. Peter's has a similar structure, using two brick shells and 16 stone ribs. The inner shell is more hemispherical while the outer is vertical. Like Brunelleschi's it is held together with a lantern topper.