How config Phalcon for PostgreSQL?

Hi!

'database' => array(
        'adapter'     => 'Postgresql',
        'host'        => 'localhost',
        'username'    => 'pgroot',
        'password'    => '*******',
        'dbname'      => 'testtop',
),

This config is not working. If I type command "phalcon model users" Phalcon-tools writing "Error: could not find driver".