Texas Instruments ULN2003APW

Overview

ULN2003APW from Texas Instruments is a 7-channel high-voltage, high-current NPN Darlington transistor array in a 16-pin TSSOP package. Each channel delivers 500mA sink current with 50V collector-emitter rating and integrated common-cathode clamp diodes. It operates directly from 3.3V or 5V TTL/CMOS logic and is used for relay, stepper motor, LED, and lamp driving in industrial control and embedded systems.

For engineers reviewing the ULN2003APW datasheet, ULN2003APW pinout, ULN2003APW application, or ULN2003APW equivalent, key selection criteria include per-channel 500mA sink capability, 2.7kΩ internal base resistors, thermal performance in TSSOP (R_θJA = 114.1°C/W), and compatibility with inductive load flyback suppression via COM-connected clamp diodes.

Technical Context

The ULN2003APW integrates seven independent Darlington pairs-each formed by cascaded NPN transistors-providing current gain up to 10,000 A/A. Its 2.7kΩ series input resistor enables direct interfacing with 3.3V/5V logic without external biasing.

It features open-collector outputs with a shared emitter (Pin 8) and a common cathode clamp node (Pin 9) for inductive kickback suppression. The device supports operation from –40°C to 70°C (ULN2003A grade) and uses standard TTL/CMOS-compatible input thresholds.

Key Specifications

Pinout & Package

TSSOP-16 package (5.00mm × 4.40mm), thermally optimized for surface-mount industrial PCBs with exposed pad option (not standard on ULN2003APW); RoHS-compliant, lead-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2003AD and ULN2003AN, the ULN2003APW offers the smallest footprint (5.00mm × 4.40mm) and highest component density, making it optimal for modern compact PCBs-though its higher thermal resistance requires careful layout with thermal vias or local copper pour when operating above 300mA per channel.

Availability

ULN2003APW is available at Aetrix Electronics and suitable for relay control, stepper motor driving, lamp/LED signage, and industrial display interface applications requiring stable component supply and long-term industrial-grade availability.

Supply support for ULN2003APW 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and consumer markets.

The ULN2003A product line was designed specifically for logic-level interfacing to medium-power inductive and resistive loads-enabling robust, cost-effective signal translation in factory automation, building controls, and electro-mechanical systems.

FAQ

What is the maximum continuous current per channel for ULN2003APW?

The ULN2003APW supports 500mA DC collector current per channel under recommended operating conditions. This rating assumes proper PCB thermal design-specifically, use of thermal vias and copper pour beneath the exposed pad (if present) and adherence to the 114.1°C/W junction-to-ambient thermal resistance. Derating is required above 70°C ambient or with multiple channels active simultaneously.

Does ULN2003APW require external flyback diodes when driving relays?

No, ULN2003APW does not require external flyback diodes when driving relays. It integrates seven common-cathode clamp diodes connected to the COM pin (Pin 9). To activate this protection, connect COM to the positive supply of the inductive load (e.g., relay coil supply). This provides a safe path for flyback current during turn-off, preventing voltage spikes that could damage the IC or upstream logic.

Can ULN2003APW interface directly with 3.3V microcontrollers?

Yes, ULN2003APW interfaces directly with 3.3V microcontrollers. Its 2.7kΩ internal series base resistors ensure sufficient input current (≈1.2mA at 3.3V) to fully saturate each Darlington pair. Verified VI(on) threshold is ≤3.0V at IC = 300mA, making it compatible with standard 3.3V CMOS logic families without level-shifting circuitry.

What is the purpose of Pin 8 (E) and Pin 9 (COM) on ULN2003APW?

Pin 8 (E) is the common emitter terminal-connect it directly to system ground to complete the current path for all seven Darlington channels. Pin 9 (COM) is the common cathode node for the integrated clamp diodes-tie it to the positive supply rail of the inductive load (e.g., 12V relay coil supply) to enable flyback energy recirculation. Leaving COM floating disables clamp functionality and risks destructive voltage spikes.

How does ULN2003APW differ from ULN2003AI in terms of temperature rating?

The ULN2003APW is rated for –40°C to +70°C operation (standard ULN2003A grade), whereas ULN2003AI extends to –40°C to +105°C. Key differences include higher V_CE(sat) max (1.7V vs 1.6V at 350mA) and increased clamp reverse current (100μA vs 50μA at 70°C) in the AI variant. ULN2003APW is intended for commercial/industrial environments with controlled ambient, not extended-temperature automotive or harsh-environment use.