Querying for an exact match on a Matrix block field with multiple types
When I understand Brandon correctly in this answer Query for blocks across Block Types using the new field parameter?, it's not possible to set up what you want with a criteria model.

What you can do though is to add additional custom query conditions to the dbCommand after running the criteria model through the buildElementsQuery function.

public function getMatrixBlocks($matrixFieldId, $fieldValue)
{
    $criteria = craft()-&gt;elements-&gt;getCriteria(ElementType::MatrixBlock);
    $criteria-&gt;fieldId = $matrixFieldId;

    $dbCommand = craft()-&gt;elements-&gt;buildElementsQuery($criteria);

    $params = array(
        ':myFieldHandle' =&gt; $fieldValue,
    );

    $conditions = array('or',
        'content.field_myBlockTypeA_myFieldHandle=:myFieldHandle',
        'content.field_myBlockTypeB_myFieldHandle=:myFieldHandle',
    );

    $dbCommand-&gt;andWhere($conditions, $params);

    return $dbCommand-&gt;queryAll();
}