Diodes Incorporated FZT558TA

Overview

FZT558TA from Diodes Incorporated is a 400V PNP high-voltage transistor in SOT223 package, designed for high-breakdown voltage switching and linear amplification in off-line power supplies and industrial controls. It delivers -400V V_CEO, -200mA continuous collector current, and V_CE(sat) < -200mV @ -20mA, enabling robust operation in flyback snubber circuits and HV DC-DC bias rails.

For engineers reviewing the FZT558TA datasheet, FZT558TA pinout, FZT558TA application, or FZT558TA equivalent, key selection criteria include verified -400V BV_CEO, h_FE ≥ 100 at -50mA, thermal resistance R_θJL = 19.41°C/W, and SOT223 lead-frame thermal performance under pulsed and DC conditions.

Technical Context

This PNP bipolar junction transistor operates with emitter-grounded configuration and supports high-voltage blocking up to -400V in both V_CBO and V_CEO ratings. Its low saturation voltage (≤ -500mV at -50mA) and stable h_FE across -1mA to -100mA enable precise current control in active clamp and gate drive stages.

The device uses a planar epitaxial die structure with optimized base doping and junction geometry to maintain gain linearity and reduce leakage (I_CBO, I_CES ≤ -100nA at -320V). Thermal design leverages the SOT223 collector tab for direct PCB copper conduction, achieving R_θJA = 41.7°C/W on 50mm × 50mm 2oz FR4.

Key Specifications

Pinout & Package

Package: SOT223 (Type DN), molded plastic with matte tin-plated leads, UL 94V-0 rated, 0.112g weight. Collector lead forms integral thermal pad soldered to PCB copper for enhanced heat dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX653 and MJD44H11T4G, FZT558TA uniquely balances 400V rating, SMT-compatible thermal performance (R_θJL = 19.41°C/W), and tight V_CE(sat) tolerance-making it optimal for compact, high-efficiency HV auxiliary and clamp functions where board area and thermal mass are constrained.

Availability

FZT558TA is available at Aetrix Electronics and suitable for off-line SMPS auxiliary bias, industrial HV sensor interface, and active clamp snubber applications requiring stable component supply and long-term manufacturability.

Supply support for FZT558TA 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 semiconductor company specializing in discrete, analog, and mixed-signal devices, with manufacturing certified to IATF 16949 and product qualification to AEC-Q101.

FZT558TA belongs to Diodes' high-voltage bipolar transistor family, engineered for reliability in industrial power conversion, automotive auxiliary systems, and HV sensing where breakdown voltage and thermal stability are critical.

FAQ

What is the maximum continuous power dissipation for FZT558TA on a standard PCB?

FZT558TA delivers 3W maximum continuous power dissipation when mounted on a 50mm × 50mm single-sided 2oz copper FR4 PCB under still-air conditions, corresponding to its R_θJA of 41.7°C/W and T_J(max) of +150°C. Derating begins above +25°C ambient per Figure 4 in DS33139 Rev. 6-2.

Is FZT558TA qualified for automotive applications?

FZT558TA is not pre-qualified to AEC-Q101, but Diodes Incorporated offers PPAP-capable manufacturing in IATF 16949-certified facilities and supports automotive change control upon request. Customers must initiate formal qualification engagement with Diodes for AEC-compliant versions.

How does the SOT223 package improve thermal performance versus SOT23?

The SOT223 package features an extended collector tab that provides direct thermal conduction to PCB copper, achieving R_θJL = 19.41°C/W-over 3× better than typical SOT23 R_θJL. This enables 2× higher continuous power handling without heatsinks in space-constrained layouts.

Can FZT558TA replace FZT458 in complementary pair designs?

FZT558TA is the PNP complement to the NPN FZT458, sharing identical SOT223 packaging, voltage ratings (-400V), and thermal characteristics. Pin-for-pin compatibility and matched h_FE curves allow direct use in push-pull, differential amplifier, and complementary switching topologies.