Using External DB with Views isn't working correct

I'm using external DB in my Drupal 7 installation. I have configured my settings.php for it and now I writing module to integrate external data with Views. I'm using parameter "database" in "base" array for external table

$data['exttable']['table']['base'] = array(
'field' => 'id',
'title' => 'External data',
'weight' => 10,
'database' => 'extdb',
);

After adding field to my Views display and trying preview it I have message
...
StatusText: Service unavailable (with message)
ResponseText: PDOException: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'drupal7.exttable' doesn't exist ...

"drupal7" is my default database for my drupal installation. It is working only if I copy my "exttable" to default database of my drupal installation.