Texas Instruments ULN2003ANS

Overview

ULN2003ANS from Texas Instruments is a 7-channel high-voltage, high-current NPN Darlington transistor array designed for logic-level interfacing to inductive and resistive loads. It delivers 500mA per channel, supports 50V collector-emitter voltage, integrates input base resistors (2.7kΩ), built-in clamp diodes, and operates with TTL/5V CMOS inputs. It is widely used in relay control, stepper motor driving, and LED lamp switching.

For engineers reviewing the ULN2003ANS datasheet, ULN2003ANS pinout, ULN2003ANS application, or ULN2003ANS equivalent, key selection considerations include per-channel current capability, integrated flyback diode configuration, thermal derating at elevated ambient temperatures, and compatibility with 3.3V/5V GPIO drive levels without external base resistors.

Technical Context

The ULN2003ANS implements seven independent Darlington pairs, each with a 2.7kΩ series input resistor enabling direct connection to 5V TTL or CMOS logic. Each channel features an open-collector output and shares a common cathode (COM) node for internal clamp diodes - essential for suppressing inductive kickback during relay or solenoid turn-off.

Its functional architecture relies on cascaded NPN transistors achieving current gain up to 10,000×, allowing low-input-current switching of high-current loads. The device operates across –40°C to 70°C (standard grade), with thermal performance governed by R_θJA = 95.0°C/W in its SOP-16 package.

Key Specifications

Pinout & Package

SOP-16 package (10.30mm × 5.30mm), surface-mount, gull-wing leads. Pin 1 marked by notch or dot; pin 8 is common emitter (E), pin 9 is common cathode (COM).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2003AD and ULN2003APW, the ULN2003ANS offers a balanced trade-off: moderate thermal resistance (95.0°C/W), industry-standard SOP-16 footprint, and proven reliability in long-lifecycle industrial controls - making it optimal for cost-sensitive, volume-manufactured relay and motor driver boards.

Availability

ULN2003ANS is available at Aetrix Electronics and suitable for relay control, stepper motor driving, and industrial lamp switching requiring stable component supply and long-term manufacturing continuity.

Supply support for ULN2003ANS 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 communications markets.

The ULN200x family was engineered for robust logic-to-load interfacing - specifically targeting relay, solenoid, lamp, and small-motor control in cost-sensitive, high-reliability industrial systems.

FAQ

What is the maximum continuous current per channel for ULN2003ANS?

The ULN2003ANS supports 500mA per channel under recommended operating conditions (T_A ≤ 70°C, proper PCB thermal relief). At higher ambient temperatures or with multiple channels active simultaneously, derating per Figure 5-4 is required - e.g., ~350mA per channel at 70°C with all 7 channels driven continuously in SOP-16 package.

Does ULN2003ANS require external flyback diodes when driving relays?

No. The ULN2003ANS includes integrated common-cathode clamp diodes connected between each collector output and the COM pin. When COM is tied to the positive side of the relay coil supply, these diodes provide complete flyback energy recirculation - eliminating the need for external diodes in standard relay driver configurations.

Can ULN2003ANS be used with 3.3V microcontrollers?

Yes. The ULN2003ANS has a 2.7kΩ internal base resistor per channel, resulting in ~1.2mA input current at 3.3V - well within typical GPIO sink capability. Verified VI(on) threshold is ≤3V at IC = 300mA, ensuring reliable turn-on with 3.3V logic without level-shifting circuitry.

How should the COM pin be connected in resistive load applications?

In purely resistive load applications (e.g., LED indicators with external anode pull-up), the COM pin may be left unconnected or tied to ground. It is only required to be connected to the positive supply rail when driving inductive loads to enable the internal clamp diodes - no current flows through COM in resistive-only use cases.

What is the thermal resistance (R_θJA) of ULN2003ANS and how does it affect design?

The ULN2003ANS in SOP-16 (NS) package has R_θJA = 95.0°C/W. With 700mW max power dissipation per channel (500mA × 1.4V), even one fully loaded channel raises junction temperature by ~66°C above ambient. Designers must ensure T_J ≤ 125°C - limiting simultaneous channel count or adding thermal copper pads to maintain reliability.