Microchip Technology 1N5240B

Overview

1N5240B from Microsemi is a 10 V, ±5% tolerance, 500 mW glass axial-lead Zener diode in DO-35 (DO-204AH) package, rated for 20 mA test current, 600 Ω maximum zener impedance at knee current, and operating across –65°C to +175°C. It serves as a precision voltage reference or shunt regulator in low-power analog circuits, power supply feedback paths, and overvoltage protection.

For engineers reviewing the 1N5240B datasheet, 1N5240B pinout, 1N5240B application, or 1N5240B equivalent, key selection criteria include its 10 V nominal zener voltage, 5% tolerance, 600 Ω dynamic impedance at 0.25 mA, temperature coefficient of +0.075 %/°C, and DO-35 mechanical compatibility with through-hole PCB layouts.

Technical Context

This device operates in reverse breakdown mode with cathode band indicating polarity; regulation occurs when the banded end is held positive relative to the anode. Its zener voltage is specified at 20 mA test current (IZT), and dynamic impedance is measured at both IZT and IZK = 0.25 mA to ensure stable knee characteristics.

The 1N5240B exhibits a positive temperature coefficient (+0.075 %/°C), confirming voltage increases with temperature - critical for thermal drift compensation in reference designs. Its 250 °C/W junction-to-lead thermal resistance supports reliable operation at full 500 mW dissipation only when leads are trimmed to 3/8″ (10 mm) from the glass body.

Key Specifications

Pinout & Package

Hermetically sealed DO-35 (DO-204AH) glass axial-leaded package with cathode indicated by a single black band; anode is unmarked lead. Leads are tin-lead or RoHS-compliant matte-tin plated, solderable per MIL-STD-750 Method 2026.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5240B, the 1N4740A offers higher power and lower impedance but requires PCB redesign, while the BZX55C10 matches the DO-35 form factor and improves leakage/impedance at lower test current - making it suitable for high-precision, low-current references where thermal margin is sufficient.

Availability

1N5240B is available at Aetrix Electronics and suitable for power supply feedback, overvoltage protection, temperature-compensated reference, and low-power sensor biasing requiring stable component supply across extended temperature ranges and long-lifecycle programs.

Supply support for 1N5240B 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

Microsemi (now part of Microchip Technology) is a U.S.-based semiconductor company specializing in high-reliability, radiation-hardened, and high-temperature analog and mixed-signal components.

The 1N52xxB series was designed for general-purpose, high-stability Zener regulation in military, aerospace, and industrial applications demanding wide temperature operation and JEDEC-standardized reliability.

FAQ

What is the nominal zener voltage and tolerance of the 1N5240B?

The 1N5240B has a nominal zener voltage of 10 V with a guaranteed tolerance of ±5%, as indicated by the "B" suffix per JEDEC specification. This means the actual breakdown voltage falls between 9.5 V and 10.5 V at 20 mA test current and 25°C ambient temperature. The 1N5240B is tested and binned to meet this tolerance band, ensuring consistent performance in voltage reference and regulation circuits.

What package type and mounting configuration does the 1N5240B use?

The 1N5240B uses a DO-35 (also designated DO-204AH) hermetically sealed glass axial-leaded package. It features two tinned leads - cathode marked by a single black band - intended for through-hole mounting. The 1N5240B must be mounted with ≥10 mm (3/8″) lead length from the glass body to achieve its rated 500 mW power dissipation and 250 °C/W thermal resistance.

What is the zener impedance of the 1N5240B and why does it matter?

The 1N5240B has a maximum zener impedance of 600 Ω at IZK = 0.25 mA, and is also characterized at IZT = 20 mA. This impedance reflects AC resistance in breakdown and directly impacts regulation stability under varying load or ripple conditions. A lower value improves voltage stiffness; the 1N5240B's 600 Ω value is typical for 500 mW Zeners in this voltage range and supports adequate regulation in low-current analog references.

Does the 1N5240B have a positive or negative temperature coefficient?

The 1N5240B has a positive temperature coefficient of +0.075 %/°C, meaning its zener voltage increases by approximately 7.5 mV per degree Celsius rise above 25°C. This behavior is confirmed in the datasheet Note 3 for devices from 1N5236 through 1N5242. Designers can leverage this predictable drift for temperature compensation when paired with negative-tempco elements in precision reference circuits using the 1N5240B.

Is the 1N5240B suitable for high-reliability or harsh-environment applications?

Yes - the 1N5240B is rated for operation from –65°C to +175°C, is inherently radiation-hardened per MicroNote 050, and is nonsensitive to ESD per MIL-STD-750 Method 1020. These attributes make the 1N5240B suitable for automotive engine control units, downhole oilfield electronics, and military-grade power conditioning where long-term stability and environmental resilience are mandatory. The 1N5240B meets JEDEC registration requirements for industrial and defense use.