Depends how the DB crashed.
If the log is still accessible and SQL's still running, then you back up the tail of the log (no truncate, no recovery options), and restore that as the last log backup when you restore the database.
If the log is not accessible (say the log drive failed), then you cannot retrieve that last 15 min of data.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability