Nexperia USA Inc. BAS321,135

Overview

BAS321 from Nexperia is a general-purpose silicon switching diode fabricated in planar technology and housed in an SOD323 (SC-76) surface-mount package. It delivers 250 mA continuous forward current, 200 V reverse voltage rating, 1.25 V forward voltage at 200 mA, 50 ns reverse recovery time, and 300 mW power dissipation - optimized for compact, high-density PCB layouts in consumer and industrial signal routing.

For engineers reviewing the BAS321 datasheet, BAS321 pinout, BAS321 application, or BAS321 equivalent, key selection criteria include its 50 ns switching speed, 250 V peak reverse voltage capability, thermal resistance of 366 K/W (junction-to-ambient), cathode/anode polarity marking (A7), and compatibility with standard FR4 reflow soldering footprints.

Technical Context

The BAS321 operates as a unidirectional PN junction rectifier with defined forward conduction and reverse blocking behavior. Its 50 ns trr and 2 pF capacitance support moderate-speed digital and analog signal switching up to ~10 MHz, while its 150 °C maximum junction temperature enables operation in thermally constrained environments.

Thermal performance is characterized by Rth(j-a) = 366 K/W on single-sided FR4 and Rth(j-sp) = 130 K/W to the cathode solder point. The device adheres to IEC 60134 absolute maximum ratings, with non-repetitive surge capability up to 9 A for 1 µs pulses and 3 A for 100 µs pulses.

Key Specifications

Pinout & Package

The BAS321 is packaged in a 2-pin SOD323 (SC-76) plastic surface-mount case measuring 1.7 mm × 1.25 mm × 0.95 mm with 1.3 mm lead pitch. The package features a molded body with visible cathode band and laser-marked "A7" identification.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar general-purpose switching diode applications.

Compared with MMBD301LT1G and BAV99W-7-F, the BAS321 uniquely balances 250 V blocking, 50 ns switching, and 250 mA current in a single-diode SOD323 form - making it optimal for cost-sensitive, space-constrained 12–24 V industrial control interfaces requiring robust transient handling.

Availability

BAS321 is available at Aetrix Electronics and suitable for USB interface protection, DC-DC snubbing, logic-level translation, and reverse-polarity input protection requiring stable component supply and consistent SOD323 packaging.

Supply support for BAS321 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

Nexperia is a global semiconductor expert focused on high-volume, high-reliability discrete and logic devices, with leadership in automotive-qualified and industrial-grade components.

The BAS321 belongs to Nexperia's general-purpose diode product line, engineered for broad applicability in consumer, industrial, and computing systems where small size, predictable switching, and thermal resilience are prioritized over ultra-high-speed or ultra-low VF.

FAQ

What is the maximum ambient temperature at which BAS321 can sustain 250 mA continuous forward current?

Per Figure 1 in the datasheet, the BAS321 supports 250 mA continuous forward current up to approximately 75 °C ambient temperature on a standard FR4 PCB with single-sided copper. Above this, derating is required - e.g., at 100 °C ambient, maximum IF drops to ~150 mA to maintain Tj ≤ 150 °C.

Does BAS321 have automotive qualification?

No. The revision history explicitly states that BAS321 was changed to non-automotive qualification in v.4 (2024). It is not AEC-Q101 qualified, and Nexperia directs users to dedicated -Q variants for automotive applications. Use in safety-critical or vehicle subsystems is not supported.

How is the cathode identified on the BAS321 package?

The cathode is marked by a visible band near pin 1 and the alphanumeric code "A7" laser-etched on the top surface of the SOD323 body. Pin 1 is the cathode (K), and pin 2 is the anode (A), as confirmed in Table 2 (Pinning information) and the simplified outline diagram.

Can BAS321 be used in place of a 1N4148 in SOD323 footprint designs?

Yes, but with trade-offs: BAS321 offers higher VRRM (250 V vs. 100 V), higher IF (250 mA vs. 300 mA), and faster trr (50 ns vs. 4 ns), yet its VF is higher (1.25 V vs. 0.72 V). It is pin-compatible in SOD323, but system-level validation is required where low forward drop or nanosecond-speed switching is critical.