Hydrolysis of (1->4)-alpha-D-glucosidic linkages in polysaccharides so as to remove successive maltose units from the non-reducing ends of the chains. Binds 1 Ca(2+) ion per subunit. Optimum temperature is 75 degrees Celsius. Stable at 80 degrees Celsius. Monomer. Belongs to the glycosyl hydrolase 14 family.