STMicroelectronics ULQ2804A

Overview

ULQ2804A from STMicroelectronics is an 8-channel Darlington transistor array with integrated clamp diodes, designed for driving inductive loads such as relays, solenoids, and stepper motor windings in industrial control systems. It features a 10.5 kΩ input resistor optimized for 6–15 V CMOS/PMOS logic interfaces, 500 mA continuous output current per channel, 50 V output voltage rating, and operates across –40 to +105 °C.

For engineers reviewing the ULQ2804A datasheet, ULQ2804A pinout, ULQ2804A application, or ULQ2804A equivalent, key selection criteria include input resistor value (10.5 kΩ), output current capability (500 mA), clamp diode integration, DIP-18 package layout, and compatibility with 6–15 V CMOS logic families.

Technical Context

The ULQ2804A integrates eight independent NPN Darlington pairs with common-emitter outputs and built-in flyback diodes-each rated for 500 mA continuous and 600 mA peak collector current. Its input stage includes a fixed 10.5 kΩ series resistor enabling direct interface to 6–15 V CMOS logic without external biasing.

It supports paralleling of outputs for higher current drive and is specified for operation up to 105 °C ambient, with thermal resistance R_thJA = 55 °C/W. The device uses a copper leadframe DIP-18 package with input pins opposite output pins to minimize PCB trace crossovers.

Key Specifications

Pinout & Package

ULQ2804A is housed in an 18-lead plastic dual in-line package (DIP-18) with copper leadframe for enhanced thermal conduction. Pin layout follows input-opposite-output configuration: inputs on one side (pins 1–8), outputs on the opposite side (pins 11–18), with common emitter (pin 9) and ground (pin 10).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2803A and TD62003APG, ULQ2804A delivers superior thermal performance (copper leadframe, R_thJA = 55 °C/W) and exact 10.5 kΩ input impedance for stable 6–15 V CMOS drive-making it optimal for high-reliability industrial controllers requiring extended temperature operation.

Availability

ULQ2804A is available at Aetrix Electronics and suitable for industrial relay drivers, stepper motor phase control, solenoid actuator interfaces, and automated test equipment load switching requiring stable component supply across long production lifecycles.

Supply support for ULQ2804A 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, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The ULQ2804A belongs to ST's high-voltage Darlington array product line, engineered specifically for ruggedized industrial interface applications demanding integrated protection, wide supply compatibility, and extended temperature reliability.

FAQ

What logic families does ULQ2804A directly interface with?

ULQ2804A is optimized for 6–15 V CMOS and PMOS logic families. Its internal 10.5 kΩ input resistor ensures proper biasing without external components when driven from CMOS outputs in that voltage range. It is not intended for 3.3 V or 5 V TTL without level translation.

Can ULQ2804A outputs be paralleled, and what is the maximum combined current?

Yes-outputs may be paralleled to increase current capacity. With proper thermal management and derating, up to four channels can be paralleled for ~2 A continuous (per group), limited by total package power dissipation (2.25 W) and junction temperature rise. Full 8-channel parallel operation requires forced-air cooling or significant derating.

Does ULQ2804A include flyback diodes, and how are they connected?

Yes-each of the eight Darlington outputs includes an integrated clamp diode connected cathode-to-V_CC and anode-to-collector. This configuration safely recirculates inductive energy during turn-off, eliminating the need for external flyback diodes in typical relay and solenoid applications.

What is the difference between ULQ2804A and ULQ2803A?

ULQ2804A uses a 10.5 kΩ input resistor for 6–15 V CMOS/PMOS logic, while ULQ2803A uses a 2.7 kΩ resistor optimized for 5 V TTL and CMOS. Their pinouts and output specs are identical, but input sensitivity and logic compatibility differ-ULQ2804A requires higher input voltage to achieve full saturation.