The product name rules for the BD9x family of buck converters are as follows.
The number "9" following "BD" indicates step-down, the following letter indicates the maximum rated input voltage, and the next number indicates the output current.

The next letter indicates the package.
・FJ: SOP-J8
・MUV: VQFN016V3030

- (hyphen) and later indicate the product rank, packaging, forming specifications, etc.
・LB: Industrial temperature grade (-40~85℃)
・H2/E2: Reel-shaped embossed taping

For details, refer to "Ordering information" in the datasheet.