Squares Upon Squares

A square of side length $l$ can be constructed out of $n$ smaller squares with integer side lengths.

If $n$ is a square number but $l$ is not and $n < l^2,$ what is the smallest possible value of $l?$

Note: Squares may be of different sizes and squares of a given size may be used more than once.

$l = 8,n = 16$