NXP Semiconductors BUK9508-55A,127

Overview

BUK9508-55A from NXP Semiconductors (formerly Philips) is an N-channel TrenchMOS™ logic-level power MOSFET in SOT78 (TO-220AB) package, designed for high-current 12 V/24 V automotive and industrial switching. It delivers 125 A DC drain current at V_GS = 5 V, 55 V V_DS, 6.8 mΩ R_DS(on) at 25 °C, 175 °C junction rating, and Q_g(tot) = 92 nC - enabling robust, low-loss control of motors, lamps, and solenoids.

For engineers reviewing the BUK9508-55A datasheet, BUK9508-55A pinout, BUK9508-55A application, or BUK9508-55A equivalent, this page provides verified thermal resistance (R_th(j-mb) = 0.59 K/W), avalanche energy (670 mJ), gate threshold (1.5 V typ), diode forward voltage (0.85 V), and SOA curves - all critical for automotive load-switch reliability and thermal design validation.

Technical Context

This discrete MOSFET uses trench-gate silicon technology to achieve ultra-low on-resistance while maintaining logic-level gate drive compatibility (V_GS(th) = 1–2 V, operational down to 4.5 V). Its mounting base is internally connected to the drain, enabling direct heatsink coupling and efficient thermal management in high-power linear or switching modes.

The device features integrated source-drain diode with 70 ns reverse recovery time and 170 nC recovered charge, supporting inductive load commutation. Avalanche ruggedness is specified at 670 mJ under unclamped inductive conditions (I_D = 75 A, V_DS ≤ 55 V), confirming suitability for automotive transient-tolerant designs without external snubbers.

Key Specifications

Pinout & Package

SOT78 (TO-220AB) plastic package with isolated mounting base electrically connected to drain terminal; requires insulating washer when mounted to grounded heatsink. Pin 1 = Gate, Pin 2 = Drain, Pin 3 = Source; mounting base (MB) is internal drain connection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with STP120N55F6 and IRF1405ZLPBF, the BUK9508-55A offers superior combination of low R_DS(on), low Q_g, and TO-220 packaging - delivering higher efficiency, faster switching, and direct drop-in replacement in space-constrained automotive modules.

Availability

BUK9508-55A is available at Aetrix Electronics and suitable for automotive starter systems, industrial HVAC actuation, and commercial vehicle lighting requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for BUK9508-55A 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 is a global semiconductor leader focused on automotive, industrial, and IoT applications, with heritage in Philips Semiconductors' high-reliability power devices.

The BUK95xx series was developed specifically for automotive power distribution and load switching, emphasizing AEC-Q101 compliance, avalanche ruggedness, and logic-level drivability in harsh environments.

FAQ

What is the maximum continuous drain current for BUK9508-55A at 100 °C mounting base temperature?

The BUK9508-55A supports 75 A continuous drain current at T_mb = 100 °C and V_GS = 5 V, as limited by package thermal constraints (not silicon). This value is confirmed in Table 3 "Limiting values" and Figure 2 of the official datasheet, where the curve caps at 75 A above 75 °C mounting temperature due to SOT78 package limitations.

Is BUK9508-55A pin-compatible with BUK9608-55A?

No, BUK9508-55A (SOT78/TO-220AB) and BUK9608-55A (SOT404/D2-PAK) have different pinouts and mechanical footprints. While both share identical electrical specifications, the SOT404 package omits pin 2 connectivity per datasheet note [1], and their mounting base geometries differ significantly - requiring separate PCB layouts and thermal interface designs.

Does BUK9508-55A include an integrated body diode, and what are its key parameters?

Yes, BUK9508-55A integrates a source-drain diode with V_SD = 0.85 V typical at I_S = 25 A and T_j = 25 °C, t_rr = 70 ns, and Q_r = 170 nC. These values are measured under specified conditions (V_GS = −10 V, V_DS = 25 V, dI_S/dt = −100 A/µs) and enable reliable freewheeling in inductive motor and solenoid loads without external diodes.

What is the gate-source voltage limit for BUK9508-55A, and why does it matter for MCU interfacing?

The BUK9508-55A has a ±15 V absolute maximum V_GS, exceeding standard ±10 V ratings. This allows safe operation with 5 V microcontrollers even under transient overvoltage conditions (e.g., ESD events), and supports robust gate drive design without clamping diodes - critical for automotive ECUs where supply rail instability is common.

How does the 0.59 K/W R_th(j-mb) of BUK9508-55A impact heatsink selection?

With R_th(j-mb) = 0.59 K/W max, total thermal resistance from junction to ambient depends primarily on heatsink performance. For example, pairing BUK9508-55A with a 5 K/W heatsink yields ~5.6 K/W total, enabling ~45 W continuous dissipation at ΔT = 250 K (175 °C − 25 °C). This simplifies thermal design versus higher-R_th alternatives requiring active cooling.