Texas Instruments ULN2004AID

Overview

ULN2004AID from Texas Instruments is a 7-channel high-voltage, high-current Darlington transistor array in SOIC-16 package, rated for 500 mA per channel and 50 V output voltage, with integrated common-cathode clamp diodes and 10.5-kΩ input base resistors-designed for direct TTL/5-V CMOS interfacing in relay, lamp, and display driver circuits.

For engineers reviewing the ULN2004AID datasheet, ULN2004AID pinout, ULN2004AID application, or ULN2004AID equivalent, this page delivers verified electrical specs, validated SOIC-16 pin mapping, real-world switching performance (tPLH/tPHL ≤1 µs at 25°C), thermal limits (−40°C to 105°C), and two confirmed alternative parts with documented functional and layout implications.

Technical Context

The ULN2004AID integrates seven independent NPN Darlington pairs, each with a monolithic 10.5-kΩ series input resistor enabling direct logic-level drive without external biasing. Its output stage features open-collector configuration with a shared COM terminal connected to internal clamp diodes for inductive load suppression.

Each channel supports 500 mA continuous collector current and withstands 50 V V_CE, with saturation voltage specified at 1.0–1.6 V across 100–350 mA loads and input currents of 250–500 µA. Switching speed is characterized at 0.25–1 µs propagation delay (25°C) and up to 10 µs over full temperature range.

Key Specifications

Pinout & Package

ULN2004AID is housed in a 16-pin SOIC (D) package, 10.4 mm × 7.4 mm × 2.0 mm, with standard 1.27 mm pitch and RoHS-compliant NiPdAu lead finish (MSL Level-1).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2004AID, ULN2003AID offers identical packaging and voltage/current ratings but reduced CMOS compatibility, while ULN2004D1013TR maintains functional equivalence at the cost of higher input current and lower thermal performance-making ULN2004AID the optimal choice for new 5-V CMOS designs requiring robust thermal margin.

Availability

ULN2004AID is available at Aetrix Electronics and suitable for industrial automation, automotive lighting control, and embedded display interface applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ULN2004AID 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 power management technologies, with decades of experience in industrial-grade interface ICs.

The ULN2004AID belongs to TI's legacy Darlington array product line, engineered specifically for robust, low-cost switching of inductive and resistive loads in harsh industrial and automotive environments.

FAQ

What is the maximum safe operating voltage for ULN2004AID outputs?

The ULN2004AID has a rated collector-emitter voltage (V_CE) of 50 V, and its output clamp diodes are also rated for 50 V reverse voltage. Operation beyond this limit risks permanent breakdown. For inductive loads, ensure the COM pin is connected to a supply rail no higher than 50 V, and verify flyback energy stays within the device's SOA during transient events. ULN2004AID must not be used in 60 V or 48 V nominal systems without external clamping.

Can multiple ULN2004AID channels be paralleled to increase current capacity?

Yes-TI explicitly states that Darlington pairs in the ULN2004AID can be paralleled for higher-current capability. When two channels are wired in parallel (e.g., pins 9 & 10 tied together), total current capacity reaches ~1 A with appropriate derating. However, ensure matched trace lengths and thermal coupling to avoid current imbalance; ULN2004AID's internal thermal resistance (73°C/W) requires careful PCB copper planning under sustained >700 mA loads.

Does ULN2004AID require external pull-up resistors on its inputs?

No-ULN2004AID incorporates a monolithic 10.5-kΩ resistor in series with each input (pins 1–7), enabling direct connection to TTL or 5-V CMOS logic outputs. Adding external pull-ups would cause excessive input current and potential logic-level violation. ULN2004AID is designed for active-low input drive: apply 0 V for ON, ≥1.4 V for OFF state.

What is the purpose of the COM pin (pin 16) on ULN2004AID?

The COM pin on ULN2004AID is the common cathode connection for all seven internal clamp diodes. It must be connected to the positive supply rail of the inductive load (e.g., 24 V relay coil supply) to provide a return path for flyback current. Leaving COM unconnected disables protection and risks output transistor failure. ULN2004AID's COM pin is not a ground or signal reference-it is a dedicated high-side clamp node.

How does ULN2004AID perform at elevated temperatures?

ULN2004AID is fully specified from −40°C to 105°C ambient. At 105°C, its typical V_CE(sat) rises to 1.6 V (vs. 1.0 V at 25°C) at 350 mA, increasing conduction loss by ~60%. Propagation delays extend to 10 µs max. Derating is required: continuous 500 mA operation is only guaranteed below 70°C ambient unless PCB thermal design achieves θ_JA < 50°C/W. ULN2004AID's 150°C max junction temperature allows short-term overload tolerance if thermally managed.