1N4957US

Overview

The Microchip Technology 1N4957US is a surface mount Zener voltage regulator with a nominal breakdown voltage of 9.1 V at a test current of 150 mA. It features a maximum dynamic impedance of 2.0 Ohms and a maximum reverse leakage current of 25 µA. The device dissipates 5 Watts of power within an operating temperature range of -65°C to +175°C. It utilizes a D-5B (E) package with a thermal resistance of 7°C/W from junction to end cap.

Feature Summary

• Hermetically sealed voidless glass construction with internal metallurgical bonds for high reliability
• Triple-layer passivation provides robust protection against environmental stressors
• Inherently radiation hard and non-sensitive to electrostatic discharge events

Applications

• High-reliability military circuits requiring MIL-PRF-19500/356 qualification
• Voltage regulation in aerospace systems where failure is not tolerated
• Power supply reference stages in harsh environment electronics

Procurement Notes

Verify the specific revision level and manufacturing origin when sourcing this component, as historical inventory may contain variations such as solid silver end caps instead of tin/lead finishes. Confirm that the supplier provides documentation attesting to the voidless hermetic seal and metallurgical bond integrity required for qualified applications.

Selection Notes

Select this component for designs requiring a 5 Watt surface mount Zener diode with strict tolerance requirements. Ensure the circuit layout accommodates the D-5B package dimensions and allows for adequate heat dissipation to maintain the junction temperature below 175°C under maximum load conditions.

Part Context

This part belongs to the 1N4954US through 1N4996US series of industry-recognized Zener regulators. These devices are designed to replace axial-leaded versions by deleting the US suffix, offering equivalent performance in a compact surface mount form factor suitable for modern PCB assembly techniques.

Replacement Considerations

Direct replacements include JAN1N4957CUS or JANTX1N4957US/TR variants which share identical electrical specifications and package outlines while adhering to stricter military screening standards.