Texas Instruments ULN2003AIDG4

Overview

ULN2003AIDG4 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. It is widely used in relay drivers, stepper motor control, and LED display interfaces.

For engineers reviewing the ULN2003AIDG4 datasheet, ULN2003AIDG4 pinout, ULN2003AIDG4 application, or ULN2003AIDG4 equivalent, key selection criteria include per-channel sink current (500mA), V_CE(sat) at defined I_C/I_B, thermal derating across duty cycle, COM pin connection requirements for inductive loads, and compatibility with 3.3V/5V logic inputs without external biasing.

Technical Context

The ULN2003AIDG4 integrates seven independent Darlington pairs-each comprising two cascaded NPN transistors-delivering β² current gain up to 10,000. Its internal 2.7kΩ series base resistor sets input current for TTL/CMOS compatibility, while 7.2kΩ and 3kΩ on-chip pulldown resistors suppress leakage and ensure reliable turn-off.

Each channel operates as an open-collector, common-emitter switch with a dedicated collector output and shared emitter (pin 8). The COM pin (pin 9) connects to the cathode of all seven integrated flyback diodes, enabling safe energy dissipation when driving relays, solenoids, or motors.

Key Specifications

Pinout & Package

ULN2003AIDG4 is packaged in a 16-pin SOIC (Small Outline Integrated Circuit) with dimensions 9.90mm × 3.91mm and standard 1.27mm pitch. The package is RoHS-compliant and rated for surface-mount reflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2003ADR, ULN2003AIDG4 offers identical functionality in a TI-specified SOIC package with documented thermal metrics (R_θJA = 88.6°C/W); versus ULN2003APG, it trades 100mA extra current capacity and extended temp range for tighter V_CE(sat) and TI's long-term supply assurance.

Availability

ULN2003AIDG4 is available at Aetrix Electronics and suitable for relay control, stepper motor interfacing, and industrial LED driving requiring stable component supply across production lifecycles.

Supply support for ULN2003AIDG4 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 technologies with over 90 years of innovation in industrial, automotive, and communications markets.

The ULN200x family was engineered for robust, cost-effective interface between low-voltage logic and high-power electromechanical loads - emphasizing reliability, integration, and ease of use in factory automation and control systems.

FAQ

What is the maximum continuous current per channel for ULN2003AIDG4?

The ULN2003AIDG4 supports 500mA continuous collector current per channel under recommended operating conditions. This rating assumes proper PCB copper area, ambient temperature ≤70°C, and appropriate duty cycle derating - for example, Figure 5-4 shows maximum current drops to ~0.45A at 50% duty cycle in SOIC package at 70°C ambient.

Can ULN2003AIDG4 drive 3.3V logic inputs directly?

Yes, ULN2003AIDG4 can interface directly with 3.3V logic. Its 2.7kΩ input resistor draws ~1.2mA at 3.3V, well within typical MCU GPIO sink capability. The device's VI(on) threshold is specified down to 2.4V at IC = 200mA, ensuring reliable turn-on with 3.3V CMOS outputs.

Is a pull-up resistor required on the output side of ULN2003AIDG4?

A pull-up resistor is required only when driving resistive loads (e.g., LEDs, lamps) to establish a logic-high voltage when the Darlington is off. For inductive loads like relays, the COM pin connects to the load's positive supply, making the pull-up unnecessary - the output floats high when inactive and sinks current when active.

How should the COM pin be connected for relay driving with ULN2003AIDG4?

For relay driving, the COM pin (pin 9) must be connected to the same positive voltage rail as the relay coil supply. This ties the cathodes of all internal clamp diodes to the coil's high-side node, allowing stored inductive energy to recirculate safely through the diode when the Darlington turns off - preventing damaging voltage spikes.

Does ULN2003AIDG4 support paralleling multiple channels for higher current?

Yes, ULN2003AIDG4 channels can be paralleled to increase sink current capacity. When two channels are paralleled, total current capability approaches 900mA (accounting for V_CE(sat) matching and thermal sharing). Derating is required - Figure 5-2 shows V_CE(sat) increases slightly with total collector current, and thermal resistance must be recalculated for combined power dissipation.