ISM-band RF transmitter IC (no RX capability). Bare bones with minimal modulation etc support.

Package

8-pin DFN.

Markings:

  NR3
  XF
  138

Die

Size is approximately x μm ( mm²)

Mask rev markings (focus stack of several images). Looks like 6 metal layers total.

Random logic showing classic UMC 180nm CMP fill pattern