Texas Instruments ULN2803ADW

Overview

ULN2803ADW from Texas Instruments is an 8-channel NPN Darlington transistor array designed for high-voltage, high-current sink switching in industrial and embedded control interfaces. Each channel delivers 500 mA collector current with 50 V output voltage rating, integrated clamp diodes, and 2.7 kΩ input base resistors enabling direct TTL/CMOS logic compatibility. It serves as a robust interface between microcontrollers and inductive loads such as relays, solenoids, and stepper motor windings.

For engineers reviewing the ULN2803ADW datasheet, ULN2803ADW pinout, ULN2803ADW application, or ULN2803ADW equivalent, key selection criteria include verified 500 mA per-channel sink capability, SOIC-18 package thermal performance (RθJA = 66.4°C/W), COM-pin–referenced flyback protection, and confirmed operation across –40°C to +85°C ambient range.

Technical Context

The ULN2803ADW implements eight independent Darlington pairs-each formed by cascaded NPN transistors-to achieve β² current gain up to 10,000, enabling 250 µA input current to drive 250 mA output load. Its internal 2.7 kΩ series base resistor and dual-stage emitter pull-down network (7.2 kΩ & 3.0 kΩ) ensure stable turn-on/turn-off behavior with 3.3 V or 5 V GPIO sources.

Operation requires external connection of the COM pin to the inductive load supply rail to activate internal cathode-common clamp diodes, suppressing flyback voltages up to 50 V. For resistive loads, COM may float while GND remains tied to system ground-enabling flexible sink-only logic-level translation without external biasing components.

Key Specifications

Pinout & Package

ULN2803ADW uses a 18-pin SOIC (DW) package measuring 11.50 mm × 7.50 mm with standard 1.27 mm pitch. The exposed pad is not thermally enhanced; thermal performance relies on PCB copper area connected to GND and COM pins.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Darlington array applications.

Compared with ULN2803AN and STMicroelectronics ULN2803A, the ULN2803ADW offers superior thermal performance in surface-mount applications, tighter V_CE(sat) control for reduced power loss, and RoHS-compliant green packaging-making it optimal for volume SMT manufacturing and thermally constrained enclosures.

Availability

ULN2803ADW is available at Aetrix Electronics and suitable for industrial control systems, factory automation interfaces, and embedded HMI backlight drivers requiring stable component supply across extended product lifecycles.

Supply support for ULN2803ADW 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and high-reliability ICs for industrial, automotive, and communications markets.

The ULN2803ADW belongs to TI's legacy power interface portfolio, engineered specifically for robust, low-cost, high-current logic-level translation in electromechanical control systems.

FAQ

What is the maximum continuous current per channel for ULN2803ADW?

The ULN2803ADW supports 500 mA continuous collector current per channel under recommended operating conditions (T_A ≤ 85°C, proper PCB thermal design). This rating assumes single-channel operation; simultaneous activation of multiple channels requires derating based on total power dissipation and thermal resistance (RθJA = 66.4°C/W for SOIC-18). Always verify junction temperature remains below 125°C using Equation 3 from the datasheet.

Can ULN2803ADW drive inductive loads without external diodes?

Yes-the ULN2803ADW includes integrated common-cathode clamp diodes connected between each output and the COM pin. When COM is tied to the inductive load's positive supply rail, these diodes provide flyback voltage suppression during turn-off. No external diodes are needed for standard relay, solenoid, or motor winding applications-reducing component count and layout complexity.

Is ULN2803ADW compatible with 3.3 V microcontrollers?

Yes-the ULN2803ADW features internal 2.7 kΩ base resistors that allow direct interfacing with both 3.3 V and 5 V logic families. With VI(on) specified at 2.4–3.0 V (typical 2.7 V), the device reliably activates at standard 3.3 V GPIO high levels. Input current remains within safe limits (~1.1 mA typical), eliminating need for external level shifters or current-limiting resistors.

What is the purpose of the GND pin on ULN2803ADW?

The GND pin (Pin 9) serves as the common emitter reference for all eight Darlington pairs. It must be connected to the system ground plane with low impedance-especially critical when sinking high currents-since all channel emitter currents return through this single node. Failure to properly route GND can cause voltage rise, inconsistent switching, or thermal runaway. Do not confuse GND with COM: GND is emitter return; COM is cathode node for clamp diodes.

Does ULN2803ADW support parallel channel operation for higher current?

Yes-the ULN2803ADW datasheet explicitly states outputs may be paralleled to increase current capability beyond 500 mA per channel. When paralleling, ensure matched trace lengths and thermal coupling to avoid current imbalance. Total current is limited by package thermal resistance and PCB copper area; for example, two channels in parallel can safely deliver ~900 mA with appropriate thermal design, leveraging the SOIC-18's RθJA = 66.4°C/W.