These are the same chip other than the 3 version features an upgraded 1GHz operating frequency with a higher 1.4 amperage rating per first paragraph in the datasheet.
Product Page Comparison:
Click here for TPS65950A2 | TPS65950A3
Applicable Part Numbers
296-24015-ND
TPS65950A2ZXN
296-24015
-296-24015-ND
-TPS65950A2ZXN-NDR
296-24015-NDR
296-24096
TPS65950A2ZXNR
296-24096-6
296-24096-1
296-24096-2
296-28190-ND
TPS65950A3ZXN
296-28190
-TPS65950A3ZXN-NDR
-296-28190-ND
296-37687
TPS65950A3ZXNR
TPS65950A3ZXNR-ND
296-37687-1
296-37687-6
296-37687-2