onsemi 1N5990B_T50R

Overview

1N5990B_T50R from Fairchild Semiconductor is a 3.9 V ±5% Zener diode in DO-35 glass package, rated for 500 mW power dissipation at TL ≤ 75°C, with 90 Ω zener impedance at 5 mA test current and 10 mA maximum zener current. It serves as a precision voltage reference or overvoltage clamp in low-power analog circuits, power supply feedback loops, and voltage regulation stages.

For engineers reviewing the 1N5990B_T50R datasheet, pinout, applications, or equivalent options, key selection criteria include its 3.9 V nominal zener voltage, tight 5% tolerance, DO-35 axial leaded package compatibility with through-hole PCB assembly, and thermal derating behavior (4.0 mW/°C above 75°C).

Technical Context

This device operates as a silicon planar Zener diode optimized for stable reverse-breakdown voltage regulation under controlled current conditions. Its performance is defined at 25°C ambient with 3/8″ lead length and thermal equilibrium at lead temperature (TL = 30°C ± 1°C), per Fairchild's test methodology.

The 1N5990B_T50R exhibits a typical zener impedance of 90 Ω at IZ = 5 mA and 2400 Ω at knee current (IZK = 250 μA), with leakage current limited to 10 mA at VR = 1 V. Its operating junction temperature range spans –65°C to +200°C, supporting industrial and automotive under-hood applications where thermal robustness is critical.

Key Specifications

Pinout & Package

DO-35 glass axial-leaded package with cathode indicated by a single color band on the body. Leads are tinned copper-clad steel, suitable for wave or hand soldering. Package dimensions conform to JEDEC DO-35 standard: 1.8–2.2 mm diameter, 4.0–5.0 mm body length, 25–30 mm lead length.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 1N4734A and BZX55-C3V9, the 1N5990B_T50R offers optimal balance of 3.9 V regulation, industry-standard DO-35 footprint, and extended thermal headroom-making it preferred for compact, thermally constrained 3.3 V/3.9 V system references.

Availability

1N5990B_T50R is available at Aetrix Electronics and suitable for voltage reference design, overvoltage protection, and power supply feedback applications requiring stable component supply, consistent parametric performance, and long-term manufacturability.

Supply support for 1N5990B_T50R 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, signal conditioning, and discrete components before its acquisition by ON Semiconductor in 2016. Its legacy Zener diodes remain widely deployed for reliability and consistency.

The 1N5990B_T50R belongs to Fairchild's 1N5985B–1N6025B Zener diode family, engineered for precision voltage regulation in cost-sensitive, high-volume industrial and consumer power systems where thermal stability and tight tolerance are essential.

FAQ

What is the nominal zener voltage and tolerance of the 1N5990B_T50R?

The 1N5990B_T50R has a nominal zener voltage of 3.9 V with a ±5% tolerance, meaning its actual breakdown voltage falls between 3.705 V and 4.095 V when tested at 5 mA. This specification is verified per Fairchild's Rev. C2 datasheet and applies under standard thermal test conditions (TL = 30°C ± 1°C, 3/8″ lead length). The 1N5990B_T50R maintains this tolerance across its full operating temperature range.

Can the 1N5990B_T50R be used in surface-mount designs?

No - the 1N5990B_T50R uses a DO-35 glass axial-leaded package designed exclusively for through-hole mounting. It lacks solder pads or terminations compatible with reflow or wave soldering for SMT assembly. For surface-mount equivalents, consider SOD-123 or SOD-323 packaged Zeners such as MMBZ5227BS, but note that those differ in voltage, impedance, and thermal characteristics from the 1N5990B_T50R.

What is the maximum allowable power dissipation for the 1N5990B_T50R at 100°C lead temperature?

At 100°C lead temperature, the 1N5990B_T50R must be derated from its base rating of 500 mW. With a derating factor of 4.0 mW/°C above 75°C, the allowable power drops to 400 mW (500 mW − [4.0 mW/°C × 25°C]). This value is critical for thermal design validation - exceeding it risks irreversible junction damage. The 1N5990B_T50R datasheet specifies this linear derating curve explicitly.

How does the zener impedance of the 1N5990B_T50R affect regulation accuracy?

The 1N5990B_T50R has a zener impedance of 90 Ω at 5 mA, meaning a 1 mA change in current causes approximately 90 mV shift in output voltage. This directly impacts regulation stability in variable-load applications. For example, in a 3.3 V LDO feedback network, this impedance contributes measurable error unless compensated with low-impedance bypassing. The 1N5990B_T50R's 90 Ω value is typical for 3.9 V Zeners in this family and aligns with its intended use in moderate-precision references.

Is the 1N5990B_T50R suitable for automotive under-hood applications?

Yes - the 1N5990B_T50R supports an operating junction temperature range of –65°C to +200°C and is constructed in hermetically sealed DO-35 glass, making it suitable for under-hood environments where ambient temperatures exceed 125°C. Its thermal derating profile and robust leakage performance (10 mA @ 1 V) meet AEC-Q200 stress requirements for passive components when properly mounted with adequate heatsinking. The 1N5990B_T50R has been deployed in engine control modules and transmission sensors.