STMicroelectronics LM237K

Overview

LM237K from STMicroelectronics is a three-terminal adjustable negative voltage regulator delivering up to −1.5 A across an output range of −1.2 V to −37 V. It features 0.01%/V typical line regulation, 0.3%/V typical load regulation, and 77 dB ripple rejection at 120 Hz with 10 µF output capacitance. Used in lab power supplies and industrial bias rails where precision, thermal stability (0.002%/W), and full on-chip protection are required.

For engineers reviewing the LM237K datasheet, LM237K pinout, LM237K application, or LM237K equivalent, key selection criteria include guaranteed −1.5 A output current, TO-220 package thermal resistance (R_thJC = 3 °C/W), adjustment pin current (65–100 µA), minimum load current (1.5–6 mA), and safe-area protection independent of ADJ terminal connection.

Technical Context

The LM237K implements an internally compensated bandgap reference and error amplifier driving a PNP pass transistor, enabling precise negative voltage regulation without external compensation. Its current-limit circuit remains active over temperature, and thermal overload protection triggers before junction damage occurs.

All protection functions-including current limit, thermal shutdown, and safe-area control-operate independently of the adjustment terminal. This ensures fail-safe behavior even if the ADJ pin is open-circuited or miswired in high-reliability systems.

Key Specifications

Pinout & Package

LM237K is housed in a TO-220 package with exposed metal tab electrically connected to the output (pin 2). The case serves as the primary heat path and must be isolated from chassis ground unless output is referenced to system ground.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM337T and LM137H, the LM237K uniquely bridges industrial reliability and extended low-temperature operation (−25°C), offering tighter thermal regulation (0.002%/W) than LM337T and lower cost than LM137H while retaining full protection functionality.

Availability

LM237K is available at Aetrix Electronics and suitable for industrial sensor bias rails, audio preamp power supplies, programmable current sinks, and lab bench power supplies requiring stable component supply and long-lifecycle support.

Supply support for LM237K 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The LM237K belongs to ST's legacy linear regulator product line, engineered specifically for high-reliability negative voltage regulation in environments demanding robust thermal performance and intrinsic fault protection without external circuitry.

FAQ

What is the minimum load current required for stable regulation with LM237K?

The LM237K requires a minimum load current of 1.5 mA at |V_I−V_O| ≤ 10 V and 2.5 mA at |V_I−V_O| ≤ 40 V to maintain regulation. This is achieved by connecting a resistor from ADJ to OUT to draw sufficient current through the internal reference, preventing output voltage rise during light-load or no-load conditions.

Can LM237K be used in parallel for higher output current?

No-LM237K is not designed for direct parallel operation due to mismatched reference voltages and thermal gradients causing current hogging. For higher current, use a single higher-rated regulator or implement external current-sharing circuitry with ballast resistors and matched thermal mounting.

What capacitor values are mandatory for stability?

A minimum 1 µF solid tantalum or 10 µF aluminum electrolytic capacitor is required on the input (C_IN) for stability. An output capacitor (C_OUT) ≥ 1 µF solid tantalum is recommended if the regulator is located >10 cm from bulk filter capacitors; larger values improve ripple rejection but require protection diodes for fault conditions.

Does LM237K require a heatsink in all applications?

A heatsink is required whenever power dissipation exceeds ~1.5 W at ambient temperatures >50°C. With R_thJC = 3 °C/W and R_thJA = 70 °C/W, junction temperature rise is calculated as P_D × (R_thJC + R_thCA + R_thA). For −1.5 A output at −15 V with −18 V input, P_D ≈ 4.5 W-necessitating a heatsink with ≤ 10 °C/W thermal resistance to stay within 125°C T_J.