CodeIgniter - Syntax error with select and where

In a precise project that shows only the active publications on the main page I am using Codeigniter, I have used the following lines of code:

Model:

$this->db->select('*');
$this->db->from("publicacoes");
$this->db->where('ativacao' == '1');
$data = $this->db->get()->result_array();

return $data;

But when I leave this line "uncommented" the application "breaks"

$this->db->where('ativacao' == '1');