STMicroelectronics ULN2004A

Overview

ULN2004A from STMicroelectronics is a 7-channel high-voltage, high-current Darlington array IC with open-collector outputs, integrated clamp diodes, 50 V output voltage rating, 500 mA continuous per channel, and CMOS/PMOS input compatibility (6–15 V). It drives inductive loads such as relays and solenoids in industrial control interfaces.

For engineers reviewing the ULN2004A datasheet, ULN2004A pinout, ULN2004A application, or ULN2004A equivalent, this device is selected for robust 7-channel low-side switching where logic-level inputs must drive 50 V/500 mA inductive loads without external flyback protection.

Technical Context

The ULN2004A integrates seven independent Darlington transistor pairs with common-emitter configuration and on-chip suppression diodes connected anode-to-V_CC, enabling direct inductive load connection without external components. Each channel operates with TTL/CMOS-compatible input thresholds optimized for 6–15 V logic families.

It uses a copper leadframe DIP-16 package to reduce thermal resistance (R_thJA = 70 °C/W), supports paralleling of outputs for up to 3.5 A total current, and maintains safe operation across –40 °C to +85 °C ambient with junction temperature limited to 150 °C.

Key Specifications

Pinout & Package

ULN2004A is supplied in a 16-pin dual in-line package (DIP-16L) with 2.54 mm pitch, copper leadframe for improved thermal performance, and industry-standard footprint compatible with through-hole PCB assembly.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2003A, ULN2004A offers higher input voltage tolerance and better noise immunity in noisy 12 V environments; compared with TBD7200A, it provides 7-channel integration and passive protection at lower system cost, though without fault feedback.

Availability

ULN2004A is available at Aetrix Electronics and suitable for industrial relay control, thermal printhead driving, solenoid valve actuation, and LED filament lamp switching requiring stable component supply across long-lifecycle embedded programs.

Supply support for ULN2004A 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The ULN2004A belongs to ST's legacy high-voltage Darlington array product line, engineered specifically for ruggedized, multi-channel low-side switching in industrial control, factory automation, and electro-mechanical interface applications.

FAQ

Can ULN2004A drive 24 V relays directly?

Yes. With its 50 V output voltage rating and integrated clamp diodes, ULN2004A safely switches 24 V DC relays by connecting the relay coil between V_CC (e.g., +24 V) and an OUT pin, and tying COM to +24 V. No external diode is required, and the 500 mA rating covers typical relay coil currents (10–200 mA).

What is the maximum ambient temperature for continuous 500 mA operation per channel?

At 85 °C ambient, the DIP-16 package's R_thJA of 70 °C/W limits total power dissipation to 0.7 W. With V_CE(SAT) ≈ 1.1 V at 500 mA, each channel dissipates 0.55 W - allowing full 500 mA per channel at 85 °C only if ≤1 channel is active. For 7-channel operation, derate to ≤200 mA per channel at 85 °C.

How does ULN2004A differ from ULN2003A in input compatibility?

ULN2004A is specified for 6–15 V CMOS/PMOS inputs, with VI(ON) ≥ 5 V (min), making it ideal for 12 V control buses. ULN2003A targets 5 V TTL/CMOS, with VI(ON) ≥ 2.4 V (min), enabling direct connection to 5 V MCUs. Input current at 12 V is 0.35–1.45 mA for ULN2004A vs. 0.93–1.35 mA for ULN2003A at 3.85 V.

Is parallel output operation supported, and what precautions apply?

Yes - outputs can be paralleled to increase current capacity. ST confirms safe paralleling of up to three channels (1.5 A total). Ensure matched PCB trace lengths and identical load connections to avoid current imbalance. Do not exceed 600 mA peak per channel even when paralleled, and verify thermal margin using R_thJA and total power.