Negative rail regulator in SOIC-8 — the 100 mA load ceiling
The LM337LMX is a negative adjustable voltage regulator in an 8-SOIC surface-mount package, delivering up to 100 mA of output current with a PSRR of 60 dB at 120 Hz. It regulates an output adjustable from -1.2 V down to -37 V, with a maximum input voltage of -40 V.
The 60 dB PSRR at 120 Hz means the regulator attenuates full-wave-rectified ripple by a factor of 1000. For a -24 V rail with 1 Vpp of 120 Hz ripple on the input, the output sees roughly 1 mVpp of ripple — adequate for most analog signal chains but not low-noise instrumentation. If the load draws near the 100 mA ceiling, the dropout voltage rises and the PSRR degrades; the datasheet curve (not reproduced here) shows the trade-off.
NRND status — lifecycle reality for the BOM
The LM337LMX carries a Not Recommended for New Design (NRND) status. Texas Instruments has flagged this part for end-of-life transition — it is not intended for new product designs. Existing production BOMs should plan a last-time-buy window and qualify a replacement before the part is formally discontinued.
Package and temperature — board-fit checklist
At 100 mA output with a 30 V input-to-output differential, the power dissipation is 3 W, which exceeds the SOIC-8's capability without a heatsink or forced air — derate the output current or reduce the differential for sustained operation.