Negative rail regulator — 1.5 A adjustable down to -37 V
The Texas Instruments LM337KTPRG3 is a negative adjustable linear voltage regulator in a TO-252-3 DPAK surface-mount package. It delivers up to 1.5 A output current with an adjustable output range from -1.2 V down to -37 V, from a maximum input voltage of -40 V. This part is the negative complement to the LM317 positive regulator family, intended for generating clean negative supply rails in dual-supply analog circuits, audio preamplifiers, and industrial control boards where PSRR matters.
The 77 dB power-supply rejection ratio at 120 Hz is the headline analog spec. It tells the designer how much of the full-wave-rectified line ripple (100/120 Hz) gets attenuated before reaching the output. For a -15 V rail feeding an op-amp front end, 77 dB rejection means the 120 Hz ripple on the unregulated input is attenuated by a factor of ~7000, keeping the supply noise floor low enough for 16-bit precision circuits. This is a genuine advantage over a three-terminal fixed regulator or a switching converter running open-loop.
DPAK footprint and thermal path
The TO-252-3 DPAK package has a large exposed copper tab on the bottom — the tab is the output pin and the primary thermal path. Without that copper area, the junction temperature rises above the 125°C maximum quickly. The 0°C lower operating limit means this part is suited for indoor, temperature-controlled equipment, not cold-start automotive or outdoor telecom cabinets.
Over-temperature and short-circuit protection
Built-in over-temperature shutdown and output short-circuit protection are included on-chip. These are thermal-foldback type protections: the die temperature sensor triggers shutdown around 165°C (typical), and the output current limiter holds the short-circuit current to a safe level. No external protection diodes are needed for most loads, though a 1 µF tantalum output capacitor is recommended for stability per the LM337 application note.
Obsolete — no official successor listed
No direct replacement order code or successor part number is provided by the manufacturer. For new designs, TI recommends evaluating the LM337 series in alternate packages (e.g., TO-220 or DDPAK) if a through-hole or larger SMD is acceptable, or migrating to a newer negative regulator family such as the TPS7A30 series for higher PSRR and lower dropout.