There are some IITs that allow outsiders to enter the college campus. Some of them include IIT Kanpur and IIT Delhi.
You can easily enter IIT Delhi and the guards will give you a visitor's pass. If you are in a vehicle, they will give you a pass card. Similarly, for IIT Kanpur if you are in a vehicle you will need to register for a pass card. However, I am not sure if IIT Tirupati has that kind of facility. I would recommend you to ask the students of IIT Tirupati or passed-out students. You can also call the college helpline to get answers to your query.