Diodes Incorporated FCX458QTA

Overview

FCX458QTA from Diodes Incorporated is a 400V NPN high-voltage transistor in SOT89 package, rated for 225mA continuous collector current and featuring V_CE(sat) < 200mV at 20mA/2mA drive. It delivers high breakdown voltage (BV_CEO = 400V), AEC-Q101 qualification, and low thermal resistance (R_θJL = 22°C/W), enabling use in automotive ignition drivers and industrial flyback snubber circuits.

For engineers reviewing the FCX458QTA datasheet, FCX458QTA pinout, FCX458QTA application, or FCX458QTA equivalent, key selection criteria include verified 400V BV_CEO, SOT89 thermal performance with exposed collector pad, AEC-Q101 compliance for automotive systems, and complementary PNP pairing with FCX558Q.

Technical Context

This NPN bipolar junction transistor operates in linear or switching mode with guaranteed BV_CEO ≥ 400V and V_CE(sat) ≤ 500mV at IC = 50mA/IB = 6mA. Its f_T = 50MHz supports medium-frequency switching, while h_FE = 100–300 across IC = 1–100mA enables stable current amplification in feedback-controlled HV stages.

The device uses an exposed-collector SOT89 thermally optimized for PCB copper area derating: R_θJA drops from 178°C/W (1oz, minimal pad) to 60°C/W (1oz, 50mm×50mm), and R_θJL = 22°C/W confirms direct heat path from die to solder joint - critical for sustained 0.7W dissipation in compact layouts.

Key Specifications

Pinout & Package

SOT89 package with exposed collector pad for thermal management; molded green compound (UL 94V-0), moisture sensitivity level 1, weight ≈ 0.055g.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN transistor applications.

Compared with FCX558Q and ZTX653, FCX458QTA uniquely combines AEC-Q101 qualification, 400V rating, SOT89 thermal efficiency, and low V_CE(sat) - making it optimal for automotive and industrial HV switching where reliability and thermal density are critical.

Availability

FCX458QTA is available at Aetrix Electronics and suitable for automotive ignition systems, industrial flyback snubbers, LED streetlight auxiliary supplies, and DC-DC converter start-up circuits requiring stable component supply with automotive-grade traceability.

Supply support for FCX458QTA 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability components for automotive, industrial, and power management markets.

The FCX458Q belongs to Diodes' high-voltage bipolar transistor product line, engineered specifically for automotive and industrial applications demanding robust 400V operation, AEC-Q101 compliance, and thermally efficient SOT89 packaging.

FAQ

What is the maximum allowable continuous collector current for FCX458QTA?

The FCX458QTA is rated for 225mA continuous collector current (I_C) at T_A = +25°C with proper PCB thermal layout. Derating applies above 25°C ambient: power dissipation drops linearly to zero at +150°C junction temperature, governed by R_θJA values dependent on copper area (e.g., 178°C/W for minimal pad, 60°C/W for 50mm×50mm).

Is FCX458QTA suitable for automotive applications?

Yes - FCX458QTA is AEC-Q101 qualified, PPAP capable, and manufactured in IATF 16949 certified facilities. It meets automotive requirements for temperature cycling (-55°C to +150°C), HBM ESD (4kV), and long-term reliability in under-hood environments such as ignition coil drivers and body control modules.

How should the exposed collector pad of the SOT89 package be handled in PCB layout?

The exposed collector pad must be soldered to a dedicated copper pour connected to the collector net. Recommended minimum pad size is 1.5mm × 1.5mm (2.25mm²); larger areas (e.g., 25mm × 25mm) reduce R_θJA to 83°C/W. Avoid thermal relief spokes - solid copper connection ensures optimal R_θJL = 22°C/W performance and mechanical stability.

What is the significance of the 'N58' marking on FCX458QTA devices?

'N58' is the product type marking code laser-etched on the device top surface. It identifies the part as FCX458Q within Diodes' SOT89 transistor family. The adjacent date code 'YWW' (e.g., '623') indicates year 2026, week 23 - used for traceability, lot control, and quality assurance in automotive and industrial supply chains.