I'm afraid we don't have any kind of setting like that, and a different IP address might not necessarily indicate a different person.
For example, if someone's download was interrupted and they had to completely restart their internet connection or retry from a different location they would be downloading from a different IP address. Blocking those would be blocking legitimate downloads.
Each download link only works a set amount of times anyway, if you are offering a simple and small file you can probably safely limit the number of attempts you allow per link to as little as 3 without creating any other problems for your buyers.