1N4991US

Single Zener Diodes Overview

The Microchip Technology 1N4991US is a surface mount Zener voltage regulator with a nominal breakdown voltage of 240 V and a maximum power dissipation of 5 Watts. It operates within a junction temperature range of -65°C to +175°C. The device features a standard voltage tolerance of ±5% and a maximum reverse leakage current of 2 µA at 182 V. Electrical characteristics include a dynamic impedance (ZZT) of 650 Ohms at the test current of 5 mA, a forward voltage of 1.50 V at 1.0 A, and a thermal resistance of 7 °C/W from junction to end cap.

Single Zener Diodes Feature Summary

• Hermetically sealed voidless-glass construction with internal metallurgical bonds for high reliability
• Military qualified to MIL-PRF-19500/356 standards
• Inherently radiation hard and non-sensitive to electrostatic discharge

Single Zener Diodes Applications

• High-reliability applications where failure cannot be tolerated
• Voltage regulation over broad operating current and temperature ranges
• Harsh environment electronics requiring robust construction

Single Zener Diodes Procurement Notes

Verify that the specific part number matches the required military qualification level and package style. Confirm compliance with environmental directives such as RoHS if applicable to the project requirements. Ensure the ordering suffix aligns with the desired tolerance or packaging format. Cross-reference the datasheet revision date to ensure the most current electrical specifications are utilized during design validation.

Single Zener Diodes Selection Notes

Select this component when a high-voltage surface mount Zener diode with 5 Watt power handling is required. The 1N4991US provides a 240 V regulation point suitable for industrial or aerospace circuits. Consider the 650 Ohm dynamic impedance for noise sensitivity in the application. Verify that the thermal management strategy accommodates the 7 °C/W junction-to-end-cap thermal resistance under expected load conditions.

Single Zener Diodes Part Context

This device belongs to the 1N4954US through 1N4996US series of surface mount Zener regulators manufactured by Microsemi, now part of Microchip Technology. These components utilize an E-package (also identified as D-5B) designed for surface mounting on printed circuit boards. The series offers a wide selection of voltage ratings from 3.3 V to 390 V, all sharing the same hermetically sealed glass package construction.

Single Zener Diodes Replacement Considerations

Axial-leaded equivalents are available by removing the US suffix, specifically the 1N4991. Other variants within the same series may offer different voltage ratings but share identical mechanical and thermal characteristics.