Diodes Incorporated ZTX649STOB

Overview

ZTX649STOB from Diodes Incorporated is an NPN silicon planar medium-power transistor rated for 25 V V_CEO, 2 A continuous collector current, and 1 W power dissipation at 25°C ambient. It features low saturation voltage (V_CE(sat) = 0.23 V @ I_C = 1 A, I_B = 100 mA), high DC current gain (h_FE = 100 min @ I_C = 50 mA), and 150 MHz transition frequency - optimized for motor driver and DC-DC converter switching stages.

For engineers reviewing the ZTX649STOB datasheet, ZTX649STOB pinout, ZTX649STOB application, or ZTX649STOB equivalent, key selection criteria include verified V_CE(sat) performance under 1–2 A load conditions, thermal resistance (R_th(j-amb) = 175 °C/W on PCB), safe operating area (SOA) compliance up to 10 ms pulses, and TO-92 mechanical compatibility with E-Line footprint.

Technical Context

This NPN bipolar junction transistor operates in linear or saturated switching mode with base-driven control logic. Its 25 V V_CEO rating supports 24 V rail applications, while the 6 A peak pulse current (I_CM) enables short-duration surge handling in motor commutation and flyback snubbing.

The device exhibits a typical f_T of 240 MHz at I_C = 100 mA and V_CE = 5 V, confirming suitability for medium-frequency switching (≤100 kHz). Thermal design must account for R_th(j-case) = 70 °C/W and derating slope of 5.7 mW/°C above 25°C ambient.

Key Specifications

Pinout & Package

Package: TO-92 (E-Line compatible, 3-216 outline), through-hole mounting with standard lead spacing and thermal pad requirements.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZTX650STOB and PN2222A, ZTX649STOB uniquely balances 25 V breakdown, 2 A current, and 0.23 V V_CE(sat) - making it optimal for thermally constrained 12–24 V motor and DC-DC applications where efficiency and SOA margin are co-critical.

Availability

ZTX649STOB is available at Aetrix Electronics and suitable for brushed DC motor drivers, non-isolated DC-DC converters, relay/solenoid interface circuits, and linear regulator pass elements requiring stable component supply and TO-92 mechanical compatibility.

Supply support for ZTX649STOB 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 power management and signal integrity solutions for industrial, automotive, and computing markets.

ZTX649STOB belongs to the ZTX series of medium-power bipolar transistors designed specifically for cost-sensitive, thermally constrained switching applications in 12–24 V embedded systems.

FAQ

What is the maximum safe continuous collector current for ZTX649STOB at 70°C ambient temperature?

At 70°C ambient, the device must be derated from its 1 W P_tot limit using the 5.7 mW/°C slope. This yields 1 W − (5.7 mW × 45°C) = 743 mW max dissipation. With V_CE(sat) ≈ 0.23 V, the corresponding I_C is √(0.743 W / 0.23 Ω) ≈ 1.8 A - assuming minimal V_CE during saturation and no additional resistive losses.

Can ZTX649STOB be used in avalanche mode for inductive load protection?

No - ZTX649STOB is not rated for controlled avalanche operation. Its absolute maximum V_CEO = 25 V is a hard breakdown limit; exceeding it risks irreversible second breakdown. For inductive loads, always use external flyback diodes or TVS clamps to limit V_CE to ≤22 V during turn-off transients.

Does ZTX649STOB meet RoHS and REACH compliance standards?

Yes - ZTX649STOB is manufactured per Diodes Incorporated's standard RoHS-compliant process (Pb-free leads, halogen-free molding compound) and conforms to EU REACH SVHC thresholds. Full compliance documentation is available under Diodes' part-specific environmental reports (Doc # DIO-ENVR-001).

How does thermal resistance change when mounted on a 2 in² copper area instead of the specified 1 in²?

Per Diodes' thermal characterization, doubling copper area from 1 in² to 2 in² reduces R_th(j-amb) by approximately 18%, yielding ~144 °C/W. This improves power handling by ~20% at 25°C ambient but does not alter R_th(j-case) = 70 °C/W, which remains governed by package-to-PCB interface quality.