STMicroelectronics LM337SP

Overview

LM337SP from STMicroelectronics is an adjustable three-terminal negative voltage regulator in TO-220 package, delivering up to −1.5 A over an output range of −1.2 V to −37 V with 0.01%/V line regulation, 0.3%/V load regulation, and 77 dB ripple rejection. It integrates current limiting, thermal overload protection, and safe-area protection-fully functional even if the adjustment pin is disconnected-and is used in lab power supplies, industrial bias rails, and programmable negative DC sources.

For engineers reviewing the LM337SP datasheet, LM337SP pinout, LM337SP application, or LM337SP equivalent, key selection criteria include guaranteed −1.5 A output current, reference voltage of −1.25 V (±3%), thermal regulation of 0.003%/W, operating junction temperature up to 125 °C, and TO-220 mechanical compatibility with standard heatsinks.

Technical Context

The LM337SP implements a bandgap-referenced error amplifier driving a PNP pass transistor, with internal current-sense circuitry enabling constant-current limiting across temperature. Its adjustment pin draws only 65–100 µA, minimizing resistor-divider loading errors in precision output setting.

Thermal regulation is specified at 0.003%/W (typical) within 10 ms of a power step, independent of line/load regulation or temperature coefficient. Ripple rejection remains ≥60 dB from 120 Hz up to 10 kHz when using recommended 10 µF output capacitance.

Key Specifications

Pinout & Package

LM337SP uses the standard TO-220 package (3-lead, vertical mounting), with metal tab electrically connected to the output terminal and designed for direct heatsink attachment. Thermal resistance is 3 °C/W junction-to-case and 70 °C/W junction-to-ambient (unmounted).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar adjustable negative voltage regulator applications.

Compared with LM337SP, LM337KTP offers tighter thermal resistance and broader temperature rating but identical regulation performance, while LD1085V trades adjustability for higher current and fixed output-making it unsuitable for variable-voltage designs despite shared TO-220 packaging.

Availability

LM337SP is available at Aetrix Electronics and suitable for laboratory power supplies, industrial analog bias rails, and programmable audio amplifier supplies requiring stable component supply, long-lifecycle availability, and consistent TO-220 mechanical fit.

Supply support for LM337SP includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power management ICs, analog chips, and MEMS sensors for industrial, automotive, and consumer markets.

The LM337 series belongs to ST's linear voltage regulator product line, engineered specifically for robust, low-noise negative rail generation in environments demanding high reliability, integrated protection, and ease of external component design.

FAQ

What is the minimum input-to-output voltage differential required for regulation?

The LM337SP requires a minimum input-to-output voltage differential of 3 V to maintain regulation across its full output range and load current. At −1.5 A output, dropout increases slightly due to pass transistor saturation; datasheet specifies 3 V as the guaranteed minimum for all conditions including temperature extremes and line/load variations.

Can the LM337SP be used in parallel for higher current output?

No-parallel operation is not supported. The LM337SP lacks built-in current-sharing circuitry, and mismatched reference voltages or thermal gradients between units cause unequal current distribution, risking thermal runaway. For higher current, use a single higher-rated regulator or a discrete pass transistor configuration with external current sensing.

Is a heat sink mandatory for continuous 1.5 A operation?

Yes. With a junction-to-ambient thermal resistance of 70 °C/W and power dissipation exceeding 10 W at typical −15 V output, the junction temperature will exceed 125 °C without heatsinking. A heatsink with ≤10 °C/W thermal resistance is required to maintain safe operation at full load and ambient temperatures up to 50 °C.

What capacitor values are mandatory for stability?

A minimum 1 µF solid tantalum or 10 µF aluminum electrolytic capacitor is required at the input pin. An output capacitor is not strictly mandatory but strongly recommended: 1 µF solid tantalum if the regulator is >10 cm from bulk filter capacitors, or 10 µF for optimal ripple rejection. Larger output capacitance (>20 µF) requires protection diodes per Figure 18 in the datasheet.