that is a very common misconception that stems from the fact that a "bitcoin ASIC" doesn't work for mining litecoin but ASIC only means Application-specific integrated circuits in simple terms it is a hardware that is designed to perform specific hashing algorithms. this algo can be SHA256 to mine bitcoin or other coins based on it or it can be some other thing so it can be used for litecoin or any other different coin.
here is an LTC ASIC miner by Bitmain which has been in use for many many years by the way: https://shop.bitmain.com/promote/antminer_l3_litecoin_asic_scrypt_miner/overview