NXP Semiconductors BSN254A,126

Overview

BSN254A,126 from NXP Semiconductors (formerly Philips) is an N-channel enhancement-mode vertical D-MOS transistor in SOT54 (TO-92) package, rated for 250 V drain-source voltage, 310 mA DC drain current, and 1 W total power dissipation at 25 °C ambient. It features low R_DS(on) of 2.8 Ω (typ.) at V_GS = 10 V and I_D = 300 mA, gate threshold voltage up to 2 V, and is optimized for line current interruption in telephone sets.

For engineers reviewing the BSN254A,126 datasheet, BSN254A,126 pinout, BSN254A,126 application, or BSN254A,126 equivalent, key selection criteria include verified R_DS(on) performance at low gate drive (2.4 V), fast switching times (6 ns turn-on, 47 ns turn-off), thermal resistance (125 K/W), and SOT54 pinout compatibility with legacy telephony driver circuits.

Technical Context

This device implements a vertical double-diffused MOS structure enabling high-voltage blocking (250 V) while maintaining low on-resistance and no secondary breakdown-critical for reliable relay and transformer driver operation. Its gate-source threshold voltage range (0.8–2 V) ensures direct interface with CMOS and TTL logic without level-shifting.

Switching behavior is characterized by C_iss = 100 pF (typ.), C_oss = 21 pF (typ.), and Cr_ss = 10 pF (typ.) at V_DS = 25 V, supporting high-speed digital control in line-powered telecom interfaces. Junction temperature is rated to 150 °C with storage range from −55 °C to +150 °C.

Key Specifications

Pinout & Package

SOT54 (TO-92 variant) plastic through-hole package with 3 leads; lead length ≤4 mm; mounting pad for drain (pin 2) must be ≥10 × 10 mm for thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar N-channel MOSFET switching applications.

Compared with BSN254A,126, the BSN10,112 offers better conduction efficiency below 60 V but sacrifices critical high-voltage line integrity, while the 2N7002,215 trades voltage capability and through-hole assembly for compactness-neither serves as a drop-in replacement in telephone line interruptor roles.

Availability

BSN254A,126 is available at Aetrix Electronics and suitable for telephone line interface design, relay driver development, and line transformer switching applications requiring stable component supply and long-lifecycle support.

Supply support for BSN254A,126 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

NXP Semiconductors, formerly Philips Semiconductors, is a global leader in high-reliability discrete semiconductors and automotive ICs, with deep heritage in telecom and industrial power devices.

The BSN254A,126 belongs to NXP's legacy vertical D-MOS transistor family designed specifically for robust, high-voltage switching in analog telephony infrastructure and electromechanical interface circuits.

FAQ

What is the maximum drain-source voltage rating for BSN254A,126?

The BSN254A,126 has a maximum drain-source voltage (V_DS) rating of 250 V DC, validated per IEC 60134 absolute maximum ratings. This rating allows safe operation in telephone line applications with 48 V nominal supply plus 170 V ringing surges, providing 30 V design margin. The BSN254A,126 maintains this rating across its full operating temperature range up to 150 °C junction temperature.

Can BSN254A,126 be driven directly by a 3.3 V microcontroller GPIO?

Yes, the BSN254A,126 can be driven directly by a 3.3 V microcontroller GPIO because its gate-source threshold voltage (V_GS(th)) is specified from 0.8 V to 2.0 V, and R_DS(on) remains low (≤7.5 Ω) even at V_GS = 2.4 V. At 3.3 V, the device achieves strong enhancement, delivering near-spec I_D and R_DS(on). The BSN254A,126 exhibits minimal gate leakage (±100 nA), ensuring stable logic-level control without external pull-downs.

What is the thermal resistance of BSN254A,126 and how does it affect PCB layout?

The BSN254A,126 has a junction-to-ambient thermal resistance (R_{th j-a}) of 125 K/W when mounted on a PCB with a minimum 10 × 10 mm copper pad under the drain lead (pin 2), and maximum lead length of 4 mm. This value means that at 1 W power dissipation, junction temperature rises 125 °C above ambient-so ambient must stay ≤25 °C for T_j ≤150 °C. The BSN254A,126 requires this specific pad layout to achieve its rated 1 W power dissipation.

How does the pinout of BSN254A,126 differ from the BSN254 version?

The BSN254A,126 uses a SOT54 variant pinout where pin 1 = source, pin 2 = drain, pin 3 = gate-whereas the BSN254 has pin 1 = gate, pin 2 = drain, pin 3 = source. This inversion is explicitly documented in the Philips datasheet and affects PCB layout compatibility: using BSN254A,126 in a BSN254 footprint will reverse gate and source connections, causing malfunction. The BSN254A,126 pinout is optimized for low-side switching configurations in telecom line drivers.

Is BSN254A,126 suitable for switching inductive loads like relays?

Yes, the BSN254A,126 is explicitly qualified for relay driver applications due to its "no secondary breakdown" characteristic-a result of its vertical D-MOS construction. This allows safe switching of inductive loads without SOA derating, even under worst-case conditions like V_DD = 50 V and I_D = 250 mA. The BSN254A,126 also features fast turn-off (47 ns typ.), reducing contact arcing and extending relay life in telecom systems.