Texas Instruments ULN2003AN

Product Overview

The Texas Instruments ULN2003AN is a 7-channel high-voltage, high-current Darlington transistor array designed for driving inductive, resistive, and switching loads in embedded and industrial electronic systems.

The device integrates seven NPN Darlington pairs with common-cathode clamp diodes, allowing direct control of loads such as relays, solenoids, stepper motors, lamps, LEDs, and other high-current devices from low-voltage logic signals. 

The ULN2003AN is one of the most widely adopted transistor driver ICs in the electronics industry due to its simple interface, low cost, high reliability, and long product lifecycle. It is commonly paired with MCUs such as 8051, AVR, PIC, STM32, Arduino-compatible controllers, and industrial control processors. 

The ULN2003AN uses a 16-pin PDIP through-hole package, making it especially popular in industrial prototypes, control boards, legacy equipment maintenance, and educational electronics.

Part Number Breakdown

ULN2003AN

Package:

• N → Plastic PDIP package, 16 pins Texas Instruments

Competitive Advantages

Comparison With Alternative Driver ICs

Key Features

1. Seven-Channel High-Current Driver

The ULN2003AN integrates seven independent Darlington transistor channels, allowing a single IC to replace multiple discrete transistor driver circuits.

Each channel supports:

• Up to 500 mA collector current
• Up to 50 V output voltage
• Parallel connection for higher current capability

This simplifies PCB design and reduces component count. Texas Instruments

Typical loads:

• Relays
• Solenoid valves
• Motors
• Lamps
• LEDs
• Electromagnetic actuators

2. Integrated Flyback Clamp Diodes

Inductive loads such as relays and motors generate reverse voltage spikes when switched off.

The ULN2003AN includes internal common-cathode clamp diodes to suppress these voltage transients.

Advantages:

• Protects the driver circuit
• Improves system reliability
• Eliminates external flyback diode requirements
• Reduces PCB complexity 

3. Direct Logic-Level Interface

The device inputs are compatible with standard TTL and CMOS logic signals.

It can be directly controlled by:

• Microcontrollers
• PLC controllers
• Digital logic circuits
• Embedded processors

Typical control voltage:

• 3.3 V logic systems (depending on current requirements)
• 5 V TTL systems

This makes it suitable as an interface between low-power logic circuits and high-current loads. 

4. Low-Side Switching Architecture

The ULN2003AN operates as a low-side driver, where the load connects to the positive supply and the IC switches the load current to ground.

Benefits:

• Simple circuit design
• High reliability
• Easy MCU control
• Suitable for industrial loads

Common applications:

• Relay control boards
• Motor driver modules
• Automation controllers

5. Mature and Long-Life Industrial Component

The ULN2003 family has been widely used for decades and remains active due to:

• Large installed base
• Simple replacement compatibility
• Stable supply chain
• Extensive design references

It is frequently used in maintenance and replacement markets where redesigning the control board is costly.

Applications

Industrial Automation

• PLC output drivers
• Industrial relay modules
• Factory control equipment
• Automation controllers

Motor Control

• Stepper motor drivers
• Small DC motor control
• Printer mechanisms
• Robotics actuators

Relay & Solenoid Driving

• Electromagnetic relays
• Solenoid valves
• Locking mechanisms
• Industrial switches

Consumer Electronics

• Display drivers
• Appliance control boards
• Smart home devices

Embedded Systems

• MCU output expansion
• GPIO current amplification
• Hardware interface circuits