Texas Instruments ULN2003APWG4

Overview

ULN2003APWG4 from Texas Instruments is a 7-channel high-voltage, high-current NPN Darlington transistor array designed for low-side switching of inductive and resistive loads. It features 500mA per channel collector current rating, 50V output voltage capability, integrated common-cathode clamp diodes, and 2.7kΩ input base resistors enabling direct TTL/5V CMOS interface - used in relay control, stepper motor phase drivers, and LED display sink arrays.

For engineers reviewing the ULN2003APWG4 datasheet, ULN2003APWG4 pinout, ULN2003APWG4 application, or ULN2003APWG4 equivalent, key selection considerations include per-channel saturation voltage (≤1.6V at 350mA), input compatibility with 3.3V/5V logic, thermal derating in TSSOP-16 package, and COM pin routing for inductive flyback suppression.

Technical Context

The ULN2003APWG4 integrates seven independent Darlington pairs, each with cascaded NPN transistors delivering current gain up to 10,000 A/A. Its 2.7kΩ series input resistor sets nominal input current to ~1.35mA at 5V, while internal 7.2kΩ/3kΩ base-emitter pull-downs minimize leakage-induced false triggering.

Operation requires tying the COM pin to the inductive load supply rail to enable clamping of flyback voltage via integrated diodes; for resistive loads, COM may float and external pull-ups are required. The device operates across –40°C to 70°C ambient temperature with junction limit of 125°C and supports parallel channel operation for higher current delivery.

Key Specifications

Pinout & Package

TSSOP-16 package (5.00mm × 4.40mm), thermally enhanced for surface-mount applications; pin 1 marked by dot or bevelled corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2003APWG4, ULN2003AD offers superior thermal performance in a larger SOIC package, while ULN2003AN provides through-hole reliability and easier rework - neither is pin-compatible with the TSSOP variant due to differing land patterns and thermal pad requirements.

Availability

ULN2003APWG4 is available at Aetrix Electronics and suitable for relay control, stepper motor interfacing, and LED display sink applications requiring stable component supply, long-term industrial lifecycle support, and RoHS-compliant packaging.

Supply support for ULN2003APWG4 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 connectivity solutions for industrial, automotive, and consumer markets.

The ULN200x family was engineered for robust, cost-effective interface between low-voltage logic and high-voltage/high-current electromechanical loads - targeting relay drivers, motor controls, and display systems since 1976.

FAQ

What is the maximum continuous current per channel for ULN2003APWG4?

The ULN2003APWG4 supports 500mA collector current per Darlington channel under recommended operating conditions. This rating assumes proper PCB thermal design - for continuous 500mA operation across multiple channels, the TSSOP-16 package requires adequate copper pour or airflow due to its 114.1°C/W junction-to-ambient thermal resistance. Derating applies above 25°C ambient.

Can ULN2003APWG4 drive 3.3V microcontroller GPIO directly?

Yes, ULN2003APWG4 can be driven directly by 3.3V GPIO. Its 2.7kΩ internal input resistor draws ~1.2mA at 3.3V, well within standard MCU output capability. The device's VI(on) threshold is ≤2.4V at 200mA load, ensuring reliable turn-on with 3.3V logic. No external level-shifting or current-limiting resistors are needed.

How must the COM pin be connected when driving relays with ULN2003APWG4?

When driving relays or other inductive loads, the COM pin of ULN2003APWG4 must be connected to the same positive supply rail as the relay coil. This enables the internal common-cathode clamp diodes to conduct flyback current safely during turn-off. Failure to connect COM results in unclamped voltage spikes that may damage the ULN2003APWG4 or upstream logic.

Is ULN2003APWG4 suitable for driving resistive loads like incandescent lamps?

Yes, ULN2003APWG4 drives resistive loads such as 12V incandescent lamps, but requires external pull-up resistors on the output pins (1C–7C) to establish a logic-high state when the Darlington is off. Unlike inductive loads, the COM pin may remain unconnected in pure resistive applications, as no flyback suppression is needed.

What is the propagation delay of ULN2003APWG4?

The ULN2003APWG4 exhibits typical propagation delays of 0.25μs to 1μs (t_PLH and t_PHL) at 25°C, as specified in the TI SLRS027T datasheet. These values apply across the full operating temperature range (–40°C to 70°C) with minor variation. The fast switching supports multiplexed LED displays and moderate-speed relay sequencing without timing bottlenecks.