BITS Pilani, the exam conducting body conduct BITSAT Entrance Exam. As per the eligibility must have secured minimum 75% marks in aggregate in Physics, Chemistry and Mathematics/ Biology in their qualifying exam or equivalent. They also need to have minimum 60% marks in each of Physics, Chemistry, and Mathematics/ Biology subjects in the qualifying exam. You can check the further eligibility of the exam with the given blow link.

https://engineering.careers360.com/articles/bitsat-eligibility-criteria

Direct Admission to Board Toppers- As per BITSAT 2019 eligibility, The Candidates who have obtained first rank in their respective Central and State boards in India for 2019 will be given direct admission to the programme of their choice, irrespective of their BITSAT 2019 scores. 

Good Luck!