about UC3843A, UCC3803, UCC38C43A

The above three pwm controllers have the same pin definitions and pin functions. It troubles me so long that what the main differences between these controllers. And who can tell me the developing aim about these controllers?

Thanks a lot! 

we do not have UCC38C43A part.

The differences between UC3843A and UCC3803 is :

http://www.ti.com/lit/ds/symlink/ucc3803.pdf 

UC3803 has the same pin configuration as the UC3843A, and also offer the added features of internal full-cycle soft start and internal leading- edge blanking of the current -sense input.

sorry, it's my mistake. the right part number should be ucc38c43.

if it can be understood like this: the ucc3803a and the ucc38C43 are the advanced versions of uc3843a.

right