LM137K

Overview

The LM137K is a three-terminal adjustable negative voltage regulator from the LM137 series, manufactured by STMicroelectronics. It operates within an extended temperature range of -55 °C to 150 °C and is housed in a TO-3 package. The device provides a guaranteed output current of 1.5 A with an adjustable output voltage range extending down to the internal reference voltage level. Key electrical specifications include a typical line regulation of 0.01%/V, load regulation of 0.3%/V, and ripple rejection of 77 dB. It features a temperature coefficient of 50 ppm/°C and includes comprehensive protection mechanisms such as thermal overload shutdown and constant current limiting.

Feature Summary

• Adjustable output voltage capability utilizing only two external resistors for configuration
• Integrated safety protections including thermal overload shutdown and short-circuit current limiting
• High performance regulation characteristics with low line and load regulation errors
• Robust construction suitable for high power dissipation environments

Applications

• Adjustable laboratory power supplies requiring stable negative rails
• Industrial equipment needing reliable negative voltage regulation
• Electronic systems utilizing electronic shutdown circuits
• Current regulator designs requiring precise negative control

Procurement Notes

Verify component authenticity through authorized distribution channels due to the prevalence of counterfeit integrated circuits. Confirm that the specific ordering code matches the required temperature grade and package style. Ensure that the procurement documentation explicitly states compliance with the manufacturer's original technical specifications. Check for any specific environmental compliance markings if required by the end application standards.

Selection Notes

Select this component when a negative voltage rail is required with an output current exceeding standard fixed regulator capabilities. The wide operating temperature range makes it suitable for harsh industrial environments where standard commercial grade parts would fail. Consider the thermal resistance characteristics of the TO-3 package during heat sink design to ensure junction temperatures remain within safe operational limits under maximum load conditions.

Part Context

This part belongs to the LM137/LM337 family of three-terminal adjustable negative regulators. While functionally similar to the LM337, the LM137 variant offers an extended military-grade temperature range compared to the commercial LM337. Both share identical pinouts and electrical performance profiles, differing primarily in their specified operating temperature ranges and qualification standards.

Replacement Considerations

Direct functional replacements include the LM337K for commercial temperature applications or generic equivalents from other manufacturers that match the TO-3 package and 1.5A current rating. Verify that substitute devices maintain the same pinout configuration and electrical parameters to ensure circuit compatibility without redesign.