Diodes Incorporated ZDT749TC

Overview

ZDT749TC from Diodes Incorporated is a dual PNP medium-power transistor in SM-8 (SOT-223-8) package, configured as two independent high-gain switching transistors with V_CEO = −25 V, I_C = −2 A continuous per die, and f_T = 100–160 MHz. It serves in compact DC-DC converter output stages and dual-channel load switching for industrial power management systems.

For engineers reviewing the ZDT749TC datasheet, ZDT749TC pinout, ZDT749TC application, or ZDT749TC equivalent, key selection criteria include verified dual-die thermal derating (22 mW/°C when both die active), low V_CE(sat) (−0.23 V @ I_C = −1 A, I_B = −100 mA), and guaranteed h_FE ≥ 70 at −50 mA, making it suitable for space-constrained, medium-current bipolar switching designs.

Technical Context

The ZDT749TC integrates two electrically isolated PNP transistors on a single SM-8 substrate, sharing no internal connection between dies. Each die supports independent biasing with separate base, emitter, and collector terminals-enabling true dual-channel operation without crosstalk.

Its design targets medium-speed switching (t_on = 40 ns, t_off = 450 ns) under pulsed conditions (300 µs width, ≤2% duty cycle), with thermal resistance θ_JA = 45.5 °C/W when both dies operate simultaneously on a 2-inch² copper PCB-critical for thermally dense power stage layouts.

Key Specifications

Pinout & Package

Package: SM-8 (8-lead SOT-223 variant), surface-mount, thermally enhanced with exposed die pad. Dual independent PNP structure with fully separated terminal sets.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual PNP switching applications.

Compared with ZDT749TC, ZXTD749N shifts implementation to low-side control with better f_T, while DMT3005LPS trades integration for higher per-device current and simpler thermal modeling-neither replicates the ZDT749TC's dual-die thermal synergy or high-side sourcing convenience.

Availability

ZDT749TC is available at Aetrix Electronics and suitable for industrial power supplies, PLC I/O modules, and HVAC actuator control requiring stable component supply with long-term manufacturability and consistent parametric performance.

Supply support for ZDT749TC 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 solutions for power management, signal integrity, and connectivity applications.

The ZDT749TC belongs to Diodes' high-reliability bipolar transistor product line, engineered specifically for thermally dense, dual-channel medium-power switching in industrial and automotive-qualified systems.

FAQ

What is the maximum allowable junction temperature for continuous dual-die operation?

The ZDT749TC has a T_j rating of −55 to +150 °C. Under continuous dual-die operation at 25 °C ambient, the 2.75 W total power limit and 45.5 °C/W θ_JA yield a theoretical ΔT of 125 °C, resulting in a max safe T_j of 150 °C-matching the absolute maximum rating. Derating is required above 25 °C ambient.

Can the two transistors be paralleled to increase current capacity?

No-ZDT749TC's two dies are electrically isolated with no internal connection. Paralleling would require external matching of h_FE, V_BE(sat), and thermal paths, which is not supported by the device architecture or characterization. Each die must be used independently per its rated I_C = −2 A limit.

Is the SM-8 package lead-free and RoHS compliant?

Yes-the ZDT749TC is manufactured with lead-free terminations and complies with EU RoHS Directive 2011/65/EU and JEDEC JS-001 ESD standards. The SM-8 package uses matte tin plating over copper alloy leads and meets IPC/JEDEC J-STD-020 moisture sensitivity level 1 (MSL1) for unlimited floor life at ≤30 °C/85% RH.

What is the recommended PCB layout for optimal thermal performance?

For best thermal performance, use ≥2 inch² of 2-oz copper connected to the exposed die pad via ≥4 thermal vias (0.3 mm diameter, filled or capped). Keep traces to C1/C2/E1/E2 ≥0.5 mm wide. Avoid placing components or ground planes directly under the die pad to maintain thermal path efficiency to the board's inner layers.