Diodes Incorporated FCX558TA

Overview

FCX558TA from Diodes Incorporated is a 400V PNP high-voltage transistor in SOT89 package, rated for -400V V_CEO, -200mA continuous collector current, and -500mA peak pulse current. It delivers low saturation voltage (V_CE(sat) < -200mV @ -20mA) and stable h_FE up to -100mA, making it suitable for high-voltage switching in industrial power supplies and flyback converters.

For engineers reviewing the FCX558TA datasheet, FCX558TA pinout, FCX558TA application, or FCX558TA equivalent, key selection criteria include verified high-voltage blocking capability (-400V), thermal performance on 15mm × 15mm copper (R_θJA = 125°C/W), complementary pairing with FCX458, and AEC-Q101 qualification for automotive-grade reliability.

Technical Context

This PNP bipolar junction transistor operates in linear or saturated switching mode with guaranteed breakdown at -400V across collector–emitter and collector–base terminals. Its h_FE remains ≥100 at -1mA and ≥30 at -100mA, supporting stable gain in high-impedance bias networks.

V_CE(sat) ≤ -0.5V at -50mA/-6mA drive enables efficient low-loss switching in high-side configurations. The exposed collector pad in SOT89 provides direct thermal path to PCB copper, enabling 1.5W power dissipation with 25mm × 25mm 1oz copper layout.

Key Specifications

Pinout & Package

Package: SOT89 - Surface-mount plastic package with exposed collector pad for enhanced thermal transfer. Molded "Green" compound (UL 94V-0), matte tin-plated leads, 0.05g weight.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX653 and BCP56-16, FCX558TA uniquely balances -400V blocking, AEC-Q101 compliance, and SOT89 thermal efficiency-making it optimal for space-constrained, high-reliability 200–400V DC applications where both voltage margin and qualification matter.

Availability

FCX558TA is available at Aetrix Electronics and suitable for industrial power supplies, automotive lighting control, AC-DC adapter protection, and telecom line interface applications requiring stable component supply and long-term lifecycle support.

Supply support for FCX558TA 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, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and North America.

The FCX558TA belongs to Diodes' high-voltage bipolar transistor product line, engineered specifically for robust switching in automotive, industrial, and telecom power systems where voltage margin, thermal reliability, and qualification compliance are critical.

FAQ

What is the maximum safe operating voltage for FCX558TA in continuous DC applications?

The FCX558TA is rated for -400V V_CEO and -400V V_CBO at T_A = +25°C. For continuous DC operation, design voltage must remain ≤80% of rated value (≤-320V) to ensure margin against temperature derating, PCB creepage, and long-term reliability per IEC 62368-1. Derating curves in the datasheet show 20% reduction at +100°C junction temperature.

Can FCX558TA replace an NPN transistor in the same circuit?

No - FCX558TA is a PNP device and cannot directly substitute for an NPN transistor without reversing bias polarity, swapping supply rails, and redesigning base drive logic. Its complementary NPN counterpart is FCX458, which shares identical SOT89 footprint, voltage/current ratings, and thermal characteristics for matched push-pull or differential pair implementations.

How does the exposed collector pad affect PCB layout and thermal performance?

The exposed collector pad in the SOT89 package must be soldered to a minimum 15mm × 15mm area of 1oz copper to achieve the specified R_θJA = 125°C/W. Smaller copper areas increase thermal resistance linearly - e.g., 10mm × 10mm raises R_θJA to ~160°C/W. Thermal vias under the pad (≥4 × 0.3mm diameter) further reduce R_θJL to 22°C/W as measured to the solder point.

Is FCX558TA suitable for use in life support equipment?

No - Diodes Incorporated explicitly prohibits use of FCX558TA in life support devices or systems without express written approval from its CEO. The device is not certified to ISO 13485 or IEC 62304, lacks failure-in-time (FIT) data for safety-critical analysis, and has no functional safety documentation (e.g., FMEDA, ASIL rating). Customers must obtain formal authorization before deployment in such applications.