onsemi 1N5370B

Overview

1N5370B from onsemi is a 5 W axial-lead Zener diode with nominal zener voltage of 56 V, ±5% tolerance, maximum zener impedance of 20 Ω at 35 mA test current, and surge rating of 280 A at 8.3 ms. It operates as a precision voltage reference or overvoltage clamp in DC power supply regulation circuits.

For engineers reviewing the 1N5370B datasheet, pinout, applications, or equivalent options, key selection criteria include its 56 V nominal breakdown, 20 Ω dynamic impedance at IZT, 1.0 μA leakage at 42.6 V, 2.3 W power derating above 25°C, and axial CASE 017AA package compatibility with through-hole PCB layouts.

Technical Context

The 1N5370B uses silicon-oxide passivated junction technology to achieve tight voltage tolerance (±5%) and stable regulation across temperature. Its thermal design relies on junction-to-lead resistance (θ_JL = 25 °C/W) and lead-length-dependent derating-power dissipation drops 40 mW/°C above 25°C ambient.

It exhibits a positive temperature coefficient typical for 56 V Zeners (~0.085 %/°C), enabling predictable drift in voltage reference designs. The device supports non-repetitive surge currents up to 280 A (8.3 ms square wave), validated per JEDEC standards using specified mounting conditions (3/8″ lead length).

Key Specifications

Pinout & Package

Package: Axial-lead, transfer-molded plastic (CASE 017AA), cathode indicated by band. Dimensions: 8.38–8.89 mm body length × 3.30–3.68 mm diameter; leads 25.4–31.75 mm long, 0.94–1.09 mm diameter.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5370B, the 1N5370BRLG offers identical regulation performance with logistics advantages for automated assembly, while the MMBZ5255BLT1G trades power handling and impedance for miniaturization-making it viable only in sub-100 mW applications where board space outweighs thermal and surge requirements.

Availability

1N5370B is available at Aetrix Electronics and suitable for industrial power supply regulation, overvoltage protection circuits, and precision reference source applications requiring stable component supply and long-term obsolescence management.

Supply support for 1N5370B 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

onsemi (Semiconductor Components Industries, LLC) is a global semiconductor supplier focused on energy-efficient technologies for automotive, industrial, cloud, and IoT applications.

The 1N53 Series belongs to onsemi's Surmetic™ 40 Zener regulator family, engineered for high-reliability DC voltage stabilization in harsh environments where thermal stability, surge resilience, and long-term parametric consistency are critical.

FAQ

What is the nominal zener voltage and tolerance of the 1N5370B?

The 1N5370B has a nominal zener voltage of 56 V with a guaranteed tolerance of ±5%, meaning its actual breakdown voltage falls between 53.2 V and 58.8 V at the specified test current of 35 mA. This tight tolerance is achieved via silicon-oxide passivated junction technology and is validated per JEDEC standards. The 1N5370B maintains this specification across its rated operating temperature range of −65°C to +200°C.

How much power can the 1N5370B dissipate continuously, and how does temperature affect it?

The 1N5370B is rated for 5 W steady-state power dissipation at lead temperature (T_L) = 25°C with 3/8″ lead length. Above 25°C, it must be derated at 40 mW/°C-so at 75°C lead temperature, maximum allowable power drops to 3 W. This derating is based on measured junction-to-lead thermal resistance (θ_JL = 25 °C/W). The 1N5370B's thermal performance assumes proper lead-to-heatsink contact per datasheet mounting guidelines.

What is the maximum surge current rating for the 1N5370B, and under what conditions is it specified?

The 1N5370B is rated for a maximum non-repetitive surge current of 280 A at a pulse width of 8.3 ms, tested per JEDEC standard conditions. This rating assumes a square-wave waveform, mounting contact located 3/8″ to 1/2″ from the diode body, and ambient temperature of 25°C ±8°C. The 1N5370B sustains this surge without parametric shift or physical damage, making it suitable for industrial transient suppression where short-duration overcurrent events occur.

Does the 1N5370B have RoHS-compliant packaging, and what does the "G" suffix indicate?

Yes, the 1N5370B is offered in Pb-free (RoHS-compliant) packaging, indicated by the "G" suffix in part numbers like 1N5370BG or 1N5370BRLG. The "G" explicitly denotes compliance with lead-free soldering requirements and environmental directives. All 1N5370B variants shipped by onsemi meet J-STD-609 Category 1 marking standards, and the 1N5370B's plastic case contains no intentionally added lead, cadmium, mercury, hexavalent chromium, or polybrominated flame retardants.

What is the zener impedance of the 1N5370B, and why does it matter in circuit design?

The 1N5370B has a maximum zener impedance (Z_ZT) of 20 Ω at its test current (I_ZT = 35 mA). This low dynamic impedance means the 1N5370B exhibits minimal voltage change under varying load currents-critical for maintaining regulation accuracy in power supply feedback loops or reference circuits. For example, a 10 mA load step results in only ~200 mV deviation in output voltage. This value is measured with 40 ±10 ms current application per datasheet methodology and applies directly to the 1N5370B's performance in real-world regulation tasks.