Fatal error in writing Excel file

[eluser]Sudz[/eluser]
hi,
I am using PHPExcel library and writing excel file using database table records.
When i write more than 1000 records in the file
it gives me
Fatal error: Out of memory (allocated 1572864) (tried to allocate 2002945 bytes) .
What setting i need to do in php.ini.
Please anyone.