  We extend the so-called singlet doublet dark matter model, where the dark
matter is an admixture of a Standard Model singlet and a pair of electroweak
doublet fermions, by a singlet scalar field. The new portal coupling of it with
the dark sector not only contributes to the dark matter phenomenology
(involving relic density and direct detection limits), but also becomes
important for generation of dark matter mass through its vacuum expectation
value. While the presence of dark sector fermions affects the stability of the
electroweak vacuum adversely, we find this additional singlet is capable of
making the electroweak vacuum absolutely stable upto the Planck scale. A
combined study of dark matter phenomenology and Higgs vacuum stability issue
reflects that the scalar sector mixing angle can be significantly constrained
in this scenario.
