Diodes Incorporated ZX5T851ASTZ

Overview

ZX5T851ASTZ from Zetex (now Diodes Incorporated) is a 60V NPN medium-power bipolar junction transistor in E-line (TO-92 variant) package, designed for low-loss switching in DC-DC converters and power drivers. Confirmed parameters: BV_CEO = 60 V, I_C = 4.5 A continuous, R_SAT = 34 mΩ at 5 A, V_CE(SAT) = 45 mV at I_C = 5 A / I_B = 200 mA, and f_T = 130 MHz. It is used in solenoid/relay drivers and backlight inverters.

For engineers reviewing the ZX5T851ASTZ datasheet, ZX5T851ASTZ pinout, ZX5T851ASTZ application, or ZX5T851ASTZ equivalent, key selection criteria include saturation voltage under high-current drive, thermal resistance (R_JA = 125 °C/W on FR4), peak pulse current capability (15 A), and E-line mechanical compatibility with through-hole PCB layouts.

Technical Context

This NPN BJT operates as a saturated switch in medium-power linear and switching applications. Its low V_CE(SAT) (≤45 mV at 5 A) and high h_FE (105 min at 5 A) enable efficient current control without external gate drivers. The device supports fast switching with t_ON = 42 ns and t_OFF = 760 ns under 1 A load conditions.

Thermal design relies on its defined R_JA values: 125 °C/W on 25 mm × 25 mm × 1.6 mm FR4 with 1 oz copper, and 175 °C/W in socket mounting. Absolute max ratings include BVCBO = 150 V, BVEBO = 7 V, and T_j range of –55 to +150 °C.

Key Specifications

Pinout & Package

E-line (TO-92 variant) package with axial leads; standardized for through-hole mounting on FR4 PCBs. Dimensions: L = 13.0–13.97 mm, D = 4.37–4.77 mm, body width = 2.16–2.41 mm. Lead pitch matches legacy TO-92 footprints.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN medium-power switching applications.

Compared with ZX5T851ASTZ, ZX5T851ASTOA differs only in packaging format (reel vs. carton), while ZX5T851A is electrically and mechanically identical - all three share the same E-line footprint, 60 V/4.5 A rating, and 45 mV saturation voltage, making them fully substitutable in design and procurement.

Availability

ZX5T851ASTZ is available at Aetrix Electronics and suitable for motor driving, solenoid control, backlight inverters, and emergency lighting circuits requiring stable component supply across industrial and embedded OEM programs.

Supply support for ZX5T851ASTZ 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

Zetex Semiconductors (acquired by Diodes Incorporated in 2008) specialized in high-performance analog and discrete semiconductors, with engineering centers in the UK, Germany, and US.

The ZX5T851A series belongs to Zetex's E-line low-saturation BJT product line, developed specifically for high-efficiency DC-DC conversion and electromechanical actuation where minimal conduction loss and robust thermal behavior are critical.

FAQ

What is the maximum safe operating temperature for ZX5T851ASTZ?

The junction temperature (T_j) must not exceed +150 °C, and storage temperature range is identical. Derating begins at 25 °C ambient: power dissipation drops linearly at 8 mW/°C above 25 °C when mounted on a 25 mm × 25 mm FR4 board with 1 oz copper.

Can ZX5T851ASTZ be driven directly by a 3.3 V microcontroller GPIO?

No - base drive requires ≥200 mA for full saturation at 5 A collector current. A 3.3 V GPIO cannot source this; a dedicated base driver stage (e.g., small-signal BJT or logic-level MOSFET buffer) is mandatory to achieve specified V_CE(SAT) and avoid thermal overstress.

Is ZX5T851ASTZ RoHS compliant?

Yes - as a post-2006 production part under Diodes Incorporated, ZX5T851ASTZ meets RoHS Directive 2011/65/EU with lead-free terminations and halogen-free molding compound, verified per JESD22-A112 and IPC-J-STD-020 standards.

Does ZX5T851ASTZ require a heatsink in typical 4.5 A applications?

Not under standard conditions: with R_JA = 125 °C/W and P_D ≈ 0.2 W (at 4.5 A × 45 mV), junction-to-ambient rise is only ~25 °C - well within limits. Heatsinking becomes necessary only if ambient exceeds 100 °C or PCB copper area is reduced below 25 mm × 25 mm.