SQLSTATE[08006] [7] invalid connection option "charset"

Hello 

I'm trying to connect with PDO to my database. 

Here is the error message : 
A Database Error Occurred
SQLSTATE[08006] [7] invalid connection option "charset"
Filename: controllers/HomeController.php
Line Number: 10

The HomeController : 

PHP Code:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class HomeController extends CI_Controller {

  

    public function __construct()
    {
        parent::__construct(); 


And the data base : 

PHP Code:

$active_group = 'default';
$query_builder = TRUE;

$db['default'] = array(
    'dsn'    => 'pgsql:host=localhost; dbname=xxx; charset=utf8;',
    'hostname' => 'localhost',
    'username' => 'root',
    'password' => 'root',
    'database' => '',
    'dbdriver' => 'pdo', 
    'dbprefix' => '',
    'pconnect' => FALSE,
    'db_debug' => (ENVIRONMENT !== 'production'),
    'cache_on' => FALSE,
    'cachedir' => '',
    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',
    'swap_pre' => '',
    'encrypt' => FALSE,
    'compress' => FALSE,
    'stricton' => FALSE,
    'failover' => array(),
    'save_queries' => TRUE
); 


It worked with mysql but I'd like to be able to use PDO. 

Any help ? 

Thank you, 
Martin.