$data = array(
    'filter_category_id' => $top_category,
    'filter_sub_category' => true,
    'sort'               => $sort,
    'order'              => $order,
    'start'              => ($page - 1) * $limit,
    'limit'              => $limit
);

$product_total = $this->model_catalog_product->getTotalProducts($data);