Microchip Technology 1N5370B/TR8

Overview

1N5370B/TR8 from Microsemi is a 5 W axial-leaded silicon Zener diode with nominal regulation voltage of 56 V, ±5% tolerance (B suffix), 20 mA test current, 35 Ω dynamic impedance at I_ZT, and maximum reverse current of 0.5 µA at 42.6 V. It operates from –65 °C to +150 °C and is used for precision voltage reference and overvoltage protection in industrial power supplies.

For engineers reviewing the 1N5370B/TR8 datasheet, 1N5370B/TR8 pinout, 1N5370B/TR8 application, or 1N5370B/TR8 equivalent, key selection criteria include Zener voltage accuracy, thermal resistance (25 °C/W junction-to-lead), surge current rating (280 A), voltage regulation (ΔV_Z = 2.3 V), and RoHS-compliant matte-tin plating per MIL-STD-750.

Technical Context

This device functions as a two-terminal voltage regulator operating in reverse breakdown mode. Its 56 V nominal Zener voltage is specified at 20 mA DC test current (I_ZT) with ±5% tolerance, and it maintains regulation across a wide current range (1–280 mA) due to low dynamic impedance (35 Ω at I_ZT) and tight knee impedance (86 Ω at 1 mA).

Thermal design relies on junction-to-lead thermal resistance of 25 °C/W at 10 mm lead length, enabling 5 W steady-state dissipation at T_L ≤ 25 °C. Reverse leakage is limited to 0.5 µA at 42.6 V (95% of V_Z), supporting stable reference performance in low-power bias networks.

Key Specifications

Pinout & Package

Package: Axial-leaded T-18 plastic case (void-free UL94V-0 epoxy), cathode indicated by band; leads are tin-lead or RoHS-compliant matte-tin plated per MIL-STD-750 Method 2026.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N5370B/TR8, the bulk-packaged 1N5370B offers identical regulation performance but lacks automated assembly support, while MMSZ5255B-TP trades power handling and impedance for miniaturization-making 1N5370B/TR8 optimal for high-reliability, high-power axial-leaded applications.

Availability

1N5370B/TR8 is available at Aetrix Electronics and suitable for industrial power supply clamping, automotive ECU protection, and battery management system sensing requiring stable component supply and long-term lifecycle continuity.

Supply support for 1N5370B/TR8 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 1N53xxB series was designed specifically for robust, high-power voltage regulation in harsh-environment applications where thermal stability, surge resilience, and JEDEC-standard interchangeability are critical.

FAQ

What is the Zener voltage tolerance of the 1N5370B/TR8?

The 1N5370B/TR8 has a Zener voltage tolerance of ±5%, as indicated by the "B" suffix in its part number. This means its actual breakdown voltage falls between 53.2 V and 58.8 V at 20 mA test current and 25 °C. The tolerance is guaranteed per JEDEC specification and verified during 100% testing. This level of accuracy supports mid-tier precision applications without requiring tighter (and more expensive) ±1% or ±2% variants like those with D or C suffixes.

Can the 1N5370B/TR8 be used in surface-mount designs?

No, the 1N5370B/TR8 is an axial-leaded T-18 package device and is not compatible with surface-mount assembly processes. For SMT equivalents, Microsemi offers the SMBJ5370B or SMBG5370B in DO-214AA (SMB) packages. These share the same 56 V ±5% regulation and 5 W rating but require different PCB layout, thermal pad design, and reflow profiles. Using 1N5370B/TR8 in SMT lines would necessitate through-hole insertion or adapter carriers, compromising reliability and process efficiency.

What is the maximum continuous power dissipation of the 1N5370B/TR8?

The 1N5370B/TR8 is rated for 5.0 W steady-state power dissipation at a lead temperature (T_L) of 25 °C with 10 mm lead length from the body. Derating is required above 25 °C at 40 mW/°C, per Figure 1 in the datasheet. When mounted on FR4 with 4 mm² copper pads, its ambient-rated power drops to 1.47 W at 25 °C due to higher junction-to-ambient thermal resistance (85 °C/W). Full 5 W operation requires direct thermal coupling to a heatsink or chassis via the leads.

Does the 1N5370B/TR8 meet RoHS requirements?

Yes, the 1N5370B/TR8 is RoHS compliant, as confirmed by the "e3" suffix in its full manufacturer designation (1N5370B/TR8, e3). This indicates lead-free matte-tin plating on the leads and compliance with Directive 2011/65/EU. The device uses void-free UL94V-0 epoxy encapsulation and meets IPC/JEDEC J-STD-020B moisture sensitivity Level 1, eliminating dry-pack requirements. No exemptions apply-the entire construction is fully RoHS-3 compliant.

How does the 1N5370B/TR8 perform under surge conditions?

The 1N5370B/TR8 is rated for a peak non-recurrent surge current (I_ZSM) of 280 A, defined as a single 8.3 ms half-sine waveform. This rating reflects its ability to absorb transient energy without parametric shift or catastrophic failure. Its low dynamic impedance (35 Ω) and robust thermal design (25 °C/W junction-to-lead) enable rapid heat dissipation during surges. Real-world validation includes MIL-STD-750 Method 5005 surge testing, confirming suitability for automotive load-dump and industrial lightning-induced transients.