Diodes Incorporated ZDT705TC

Overview

ZDT705TC from Diodes Incorporated is a dual PNP medium-power Darlington transistor in SM-8 (SOT-223-8) package, featuring two independent high-gain, high-voltage switching elements with V_CEO = −120 V, I_C = −1 A per die, and h_FE ≥ 3000 at I_C = −10 mA. It is used in industrial relay drivers, solid-state output modules, and high-side load switches requiring robust negative-rail amplification.

For engineers reviewing the ZDT705TC datasheet, ZDT705TC pinout, ZDT705TC application, or ZDT705TC equivalent, key selection criteria include guaranteed h_FE ≥ 3k at low base drive, dual-die thermal derating behavior (22 mW/°C when both active), V_CE(sat) ≤ −2.5 V at I_C = −2 A, and −140 V V_CBO rating for transient overvoltage resilience.

Technical Context

The ZDT705TC integrates two discrete PNP Darlington pairs on a single SM-8 substrate, each with cascaded emitter-follower gain stages delivering h_FE up to 30k at I_C = −2 A. Its V_CE(sat) remains ≤ −2.5 V under pulsed −2 A loads with −2 mA base drive, enabling efficient switching in DC-controlled power rails.

Thermal design requires attention to dual-die power sharing: total dissipation reaches 2.75 W only when both transistors operate equally, while single-die operation is limited to 2.25 W with 18 mW/°C derating. Junction-to-ambient thermal resistance is 45.5 °C/W under balanced dual-die conditions on a 2-inch² copper PCB.

Key Specifications

Pinout & Package

Package: SM-8 (8-lead SOT-223 variant), surface-mount, thermally enhanced with exposed thermal pad. Pin assignment verified per Diodes Inc. datasheet ZDT705 Rev. 1 (Nov 1995).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZXTP2012Z and MBT3906DW1T1G, ZDT705TC uniquely delivers dual Darlington gain, −120 V blocking, and 2.75 W dual-die dissipation-making it irreplaceable for industrial −100 V bus switching where base drive efficiency and thermal headroom are design constraints.

Availability

ZDT705TC is available at Aetrix Electronics and suitable for industrial relay drivers, solid-state output modules, and high-side load switches requiring stable component supply across extended temperature and high-voltage operating conditions.

Supply support for ZDT705TC 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 and manufacturing operations across Asia and the Americas.

ZDT705TC belongs to Diodes' high-voltage bipolar transistor product line, engineered specifically for industrial control, programmable logic controller (PLC) output stages, and ruggedized power interface applications demanding reliability at −55 °C to +150 °C.

FAQ

What is the maximum continuous current per channel for ZDT705TC?

The ZDT705TC supports −1 A continuous collector current per Darlington channel at T_amb = 25 °C. Derating applies above 25 °C: 18 mW/°C per active die. At 100 °C ambient, max continuous current drops to approximately −0.6 A per channel based on thermal limits and V_CE(sat) stability.

Can ZDT705TC be used in parallel configurations for higher current?

No-ZDT705TC is not designed for paralleling. Its Darlington structure exhibits negative temperature coefficient in V_BE(sat), causing current hogging if multiple units share a common load. For >−1 A per channel, use a single higher-rated device or redesign with external current-sharing resistors and matched thermal mounting.

Does ZDT705TC include built-in base-emitter resistors?

No. ZDT705TC has no internal base-emitter resistors. External base resistors must be used to limit I_B and ensure proper saturation. Typical designs use 1–10 kΩ series resistors between MCU GPIO and B1/B2 pins to deliver −1 mA to −10 mA base current depending on load current and required h_FE margin.

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

Yes. Per Diodes Incorporated's official product change notice (PCN-2018-003), all ZDT705TC devices manufactured after Q2 2018 are fully RoHS-compliant and feature lead-free matte tin plating on all terminals, including the exposed thermal pad. Legacy lots may carry SnPb finish but are clearly marked and discontinued.