  We study a supergravity model of inflation essentially depending on one
parameter which can be identified with the slope of the potential at the
origin. In this type of models the inflaton rolls at high energy from negative
values and a positive curvature potential. At some point defined by the
equation $\eta=1$ inflation starts. The potential curvature eventually changes
to negative values and inflation ends when $\eta=-1$. No spontaneous symmetry
breaking type mechanism for inflation of the new type to occur is here
required. The model naturally gives a bounded $\it{total}$ number of e-folds
which is typically close to the required number for observable inflation and it
is independent of the initial conditions for the inflaton. The energy scale
introduced is fixed by the amplitude of the anisotropies and is of the order of
the supersymmetry breaking scale. The model can also accommodate an spectral
index bigger or smaller than one without extreme fine tuning. We show that it
is possible to obtain reasonable numbers for cosmological parameters and, as an
example, we reproduce values obtained recently by Tegmark $\it{et. al.}$, from
WMAP and SDSS data alone.
