Process for the preparation of a catalyst system suitable for olefin polymerization, said process comprising the steps of: providing a magnesium-based support; optionally activating said magnesium-based support; contacting said magnesium-based support with a Ziegler-Natta catalytic species, and one or more internal electron donors to yield a procatalyst, and contacting said procatalyst with a co-catalyst and at least one external donor; wherein the at least one external electron donor is n-propyltriethoxysilane and wherein the internal electron donor is selected from aminobenzoates represented by Formula XI: wherein: R 80, R 81, R 82, R 83, R 84, R 85, and R 86 are independently selected from a group consisting of hydrogen, C 1 -C 10 straight and branched alkyl; C 3 -C 10 cycloalkyl; C 6 -C 10 aryl; and C 7 -C 10 alkaryl and aralkyl group; wherein R 81 and R 82 is each a hydrogen atom and R 83, R 84, R 85 and R 86 are independently selected from a group consisting of C 1 -C 10 straight and branched alkyl; C 3 -C 10 cycloalkyl; C 6 -C 10 aryl; and C 7 -C 10 alkaryl and aralkyl group, preferably from C 1 -C 10 straight and branched alkyl and more preferably from methyl, ethyl, propyl, isopropyl, butyl, t-butyl, phenyl group; wherein when one of R 83 and R 84 and one of R 85 and R 86 has at least one carbon atom, then the other one of R 83 and R 84 and of R 85 and R 86 is each a hydrogen atom; wherein R 87 is selected from a group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, t-butyl, phenyl, benzyl, substituted benzyl and halophenyl group; and wherein R 80 is selected from the group consisting of C 6 -C 10 aryl; and C 7 -C 10 alkaryl and aralkyl group; preferably, R 80 is substituted or unsubstituted phenyl, benzyl, naphthyl, ortho-tolyl, para-tolyl or anisol group, and more preferably R 80 is phenyl. providing a magnesium-based support; optionally activating said magnesium-based support; contacting said magnesium-based support with a Ziegler-Natta catalytic species, and one or more internal electron donors to yield a procatalyst, and contacting said procatalyst with a co-catalyst and at least one external donor; wherein the at least one external electron donor is n-propyltriethoxysilane and wherein the internal electron donor is selected from aminobenzoates represented by Formula XI: R 80, R 81, R 82, R 83, R 84, R 85, and R 86 are independently selected from a group consisting of hydrogen, C 1 -C 10 straight and branched alkyl; C 3 -C 10 cycloalkyl; C 6 -C 10 aryl; and C 7 -C 10 alkaryl and aralkyl group; wherein R 81 and R 82 is each a hydrogen atom and R 83, R 84, R 85 and R 86 are independently selected from a group consisting of C 1 -C 10 straight and branched alkyl; C 3 -C 10 cycloalkyl; C 6 -C 10 aryl; and C 7 -C 10 alkaryl and aralkyl group, preferably from C 1 -C 10 straight and branched alkyl and more preferably from methyl, ethyl, propyl, isopropyl, butyl, t-butyl, phenyl group; wherein when one of R 83 and R 84 and one of R 85 and R 86 has at least one carbon atom, then the other one of R 83 and R 84 and of R 85 and R 86 is each a hydrogen atom; wherein R 87 is selected from a group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, t-butyl, phenyl, benzyl, substituted benzyl and halophenyl group; and wherein R 80 is selected from the group consisting of C 6 -C 10 aryl; and C 7 -C 10 alkaryl and aralkyl group; preferably, R 80 is substituted or unsubstituted phenyl, benzyl, naphthyl, ortho-tolyl, para-tolyl or anisol group, and more preferably R 80 is phenyl.