That means Texas Instruments still manufactures the part for existing designs, but it is not targeted for new socket wins. For a new design, a pin-compatible alternative within the DS90LV047 family should be evaluated before the layout is frozen.
400 Mbps per channel — the so-what on signal integrity
At 400 Mbps the DS90LV047ATMTC handles 200 MHz clock rates or 400 Mbps serial data streams on each of its four outputs. The LVDS swing (~350 mV differential) keeps EMI low, but the edge rates are fast enough that PCB trace impedance matching (100 Ω differential) and stub length matter. Expect to keep the driver within an inch of the connector or cable launch point to avoid reflections that eat into the receiver's input threshold margin.
Sourcing reality for the DS90LV047ATMTC
For a production BOM line that already uses this order code, the supply posture is stable for the near term — but locking in a second-source or a forward-looking replacement is prudent if the design has a multi-year production horizon.