The Infineon BSS138NL6327HTSA1 is a 60 V, 230 mA N-channel enhancement-mode MOSFET from the SIPMOS® family, housed in a PG-SOT23 package. The 1.4 nC typical gate charge keeps switching losses low in low-frequency or signal-level switching roles.
Infineon lists the BSS138NL6327HTSA1 as obsolete. If your design can tolerate a pin-compatible alternative, the standard BSS138 (without the NL6327HTSA1 suffix) is a common cross-shop candidate, but its lifecycle should be verified independently.
Rds(on) and gate drive — sizing the load switch
The 3.5 ohm maximum on-resistance at 230 mA and 10 V gate bias is the headline spec for voltage drop and self-heating. At 230 mA continuous, the dissipation is I²R = 0.23² × 3.5 ≈ 185 mW, which sits inside the 360 mW package limit at 25 °C ambient. If the gate drive is only 4.5 V, expect Rds(on) to roughly double — the datasheet's drive voltage column lists both 4.5 V and 10 V thresholds. For a 3.3 V logic gate, the part may not fully enhance; check the Vgs(th) max of 1.4 V at 250 µA, but the on-resistance at Vgs below 4.5 V is not characterised in the record.