Hi Irfan,
[quote user="Irfan Sehic"]What would be the minimal freq. considering I use the DDR3 RAM.[/quote]
Please check section 5.4 in the AM335X Datasheet Rev. G.
You can also check these wiki pages (depending on which SDK you use):
http://processors.wiki.ti.com/index.php/AM335x_Linux_Power_Management_User_Guide (SDK 6.0)
http://processors.wiki.ti.com/index.php/Linux_Core_Power_Management_User's_Guide (SDK 7.0)
http://processors.wiki.ti.com/index.php/AM335x_Power_Management_User_Guide