Microchip Technology 1N972A

Overview

1N972A from Microsemi is a silicon 500 mW axial-lead Zener diode with nominal Zener voltage 30 V, ±10% tolerance (A suffix), 49 Ω dynamic impedance at 4.2 mA test current, and maximum reverse leakage of 5 μA at 22.8 V. It operates from –65 °C to +175 °C and is used for precision voltage reference and overvoltage protection in low-power analog circuits.

For engineers reviewing the 1N972A datasheet, 1N972A pinout, 1N972A application, or 1N972A equivalent, key selection criteria include its DO-35 glass package, 30 V regulation point, thermal resistance of 250 °C/W (junction-to-lead), JEDEC-registered construction, and compatibility with through-hole PCB assembly requiring stable low-power voltage clamping.

Technical Context

The 1N972A functions as a two-terminal voltage reference device operating in reverse breakdown mode. Its Zener voltage is specified at 4.2 mA test current with 49 Ω dynamic impedance, and it exhibits a +0.091 %/°C temperature coefficient - typical for mid-voltage Zeners in the 24–36 V range.

It is rated for 500 mW steady-state power dissipation at lead temperature <50 °C (3/8″ from body), derates linearly above that, and supports surge currents up to 65 mA (1/120 sec pulse). Polarity is marked by cathode band; operation requires cathode positive relative to anode.

Key Specifications

Pinout & Package

DO-35 (DO-204AH) glass axial-leaded package: hermetically sealed, cathode indicated by colored band, tin-lead solderable terminals per MIL-STD-750 Method 2026, weight 0.2 g.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N972B and MMBZ5256BLT1G, the 1N972A offers the lowest-cost through-hole solution for non-critical 30 V clamping, with superior power handling (500 mW) and proven reliability in high-temperature and radiation environments - but requires manual or wave-solder assembly.

Availability

1N972A is available at Aetrix Electronics and suitable for industrial sensor signal conditioning, legacy power supply overvoltage clamp, and aerospace avionics bias reference requiring stable component supply across extended temperature and radiation-exposed deployments.

Supply support for 1N972A 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 analog and mixed-signal components for aerospace, defense, and industrial markets.

The 1N957B–1N992B series was designed specifically for ruggedized voltage regulation in mission-critical systems where long-term stability, radiation tolerance, and wide-temperature operation are mandatory.

FAQ

What is the Zener voltage tolerance for 1N972A?

The 1N972A has a nominal Zener voltage of 30 V with ±10% tolerance, as indicated by the "A" suffix per JEDEC standard. This means the actual measured V_Z at 4.2 mA test current falls between 27 V and 33 V at 25 °C. The tolerance reflects manufacturing spread and is verified per Microsemi's qualification testing on the 1N972A production lot.

Can 1N972A be used in surface-mount designs?

No - the 1N972A is packaged exclusively in the axial-leaded DO-35 (DO-204AH) glass case and is not compatible with SMT reflow or pick-and-place processes. For surface-mount equivalents, consider Microsemi's MLL972B in DO-213AA (MELF) or ON Semiconductor's MMBZ5256BLT1G in SOT-23 - neither is a drop-in replacement for the 1N972A.

What is the maximum surge current rating for 1N972A?

The 1N972A supports a maximum surge current (I_ZSM) of 65 mA for a 1/120 second duration, defined as a square-wave or equivalent half-sine pulse. This rating applies under specified test conditions and assumes proper PCB thermal relief; exceeding this value risks irreversible junction damage in the 1N972A.

Does 1N972A require heatsinking in standard operation?

No additional heatsink is required for the 1N972A when operated ≤500 mW at lead temperature ≤50 °C (measured 3/8″ from body). Its thermal resistance is 250 °C/W junction-to-lead, so at 500 mW dissipation, junction temperature rises ~125 °C above lead temperature - remaining within the –65 °C to +175 °C rating if leads are adequately copper-traced per Microsemi's FR4 mounting guidance.

Is 1N972A RoHS compliant?

The base 1N972A is not RoHS compliant; it uses standard tin-lead (Sn/Pb) plating. To obtain RoHS-compliant versions, Microsemi specifies the "e3" suffix (e.g., 1N972Ae3), which denotes annealed matte-tin plating meeting EU Directive 2011/65/EU. Always verify suffix configuration before ordering, as 1N972A and 1N972Ae3 are distinct orderable parts.