How to set separator for csv row using phpoffice/phpspreadsheet?

Using in my laravel 5.7 app I installed "phpoffice/phpspreadsheet": "^1.6" and reading csv file with method

$filename = public_path('/upload/csv/clients.csv');

$reader = new \PhpOffice\PhpSpreadsheet\Reader\Csv();
$spreadsheet = $reader->load($filename);

I got invalid data : looks like any row is splitted by backspace, not by comma,which is usually valid separator for csv. How to set separator for csv file lines for this lib ?

Thanks!

via Chebli Mohamed