  In this paper, we analyze the upper critical field of four MgB2 thin films,
with different resistivity (between 5 to 50 mWcm) and critical temperature
(between 29.5 to 38.8 K), measured up to 28 Tesla. In the perpendicular
direction the critical fields vary from 13 to 24 T and we can estimate 42-57 T
range in other direction. We observe linear temperature dependence even at low
temperatures without saturation, in contrast to BCS theory. Considering the
multiband nature of the superconductivity in MgB2, we conclude that two
different scattering mechanisms influence separately resistivity and critical
field. In this framework, resistivity values have been calculated from Hc2(T)
curves and compared with the measured ones.
