Allegro MicroSystems ULN2069B

Overview

ULN2069B from STMicroelectronics is a quad NPN Darlington transistor array with integrated clamp diodes and pre-driver stage, designed for interfacing 5 V logic to high-current inductive loads such as relays, solenoids, and lamps. It delivers up to 1.5 A per channel, supports 80 V output breakdown voltage, sustains 50 V at 100 mA, and features 2.5 kΩ input resistor for reduced logic loading.

For engineers reviewing the ULN2069B datasheet, ULN2069B pinout, ULN2069B application, or ULN2069B equivalent, key selection criteria include per-channel current capability (1.5 A), integrated flyback diode configuration, input resistor value (2.5 kΩ), saturation voltage at rated current (1.5 V @ 1.5 A), and PowerDIP-16 thermal performance under ambient conditions up to +85 °C.

Technical Context

The ULN2069B integrates four independent Darlington pairs with monolithic suppression diodes connected anode-to-emitter, enabling direct drive of inductive loads without external snubbers. Each channel includes a 2.5 kΩ series input resistor and internal base resistors optimized for logic-level turn-on at VI(ON) = 2.75 V (min) with II(ON) = 0.55 mA (typ) at that voltage.

It operates with common-emitter outputs and shared emitter pins (pins 8 and 16), requiring external load connection between VCC and collector terminals. Thermal design relies on PCB copper area or heatsink attachment via GND pins (pins 1, 9, 10, 11, 12, 13, 14, 15) to maintain junction temperature below 150 °C at up to 4.3 W dissipation.

Key Specifications

Pinout & Package

ULN2069B is housed in a PowerDIP-16 package with 0.3-inch body width, 2.54 mm lead pitch, and exposed substrate for thermal conduction. GND pins (1, 9–15) are internally tied to the die substrate and must be soldered to PCB ground plane or heatsink.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2067B and ULN2065B, the ULN2069B provides the lowest input current demand for 5 V logic while retaining full 80 V/1.5 A capability - making it optimal for resource-constrained embedded controllers where GPIO loading and power efficiency are critical.

Availability

ULN2069B is available at Aetrix Electronics and suitable for industrial relay control, automotive lamp driving, printer solenoid actuation, and HVAC damper motor interfacing requiring stable component supply and long-term production continuity.

Supply support for ULN2069B 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, specializing in power management, analog, microcontrollers, and discrete devices for industrial, automotive, and consumer markets.

The ULN2069B belongs to ST's high-voltage Darlington array product line, engineered specifically for robust logic-to-load interfacing in harsh industrial environments with minimal external components.

FAQ

What is the maximum continuous output current per channel for ULN2069B?

The ULN2069B supports 1.5 A continuous DC current per channel at T_AMB = 70 °C with adequate PCB copper heatsinking. At higher ambient temperatures or without thermal enhancement, derating applies - e.g., 1.25 A at 85 °C ambient with 4.3 W total package dissipation limit.

Can ULN2069B drive inductive loads without external diodes?

Yes. ULN2069B integrates monolithic clamp diodes connected anode-to-emitter for each Darlington pair, providing complete flyback protection for relays, solenoids, and DC motors. No external diodes are required unless higher voltage clamping or faster recovery is needed.

How does the 2.5 kΩ input resistor affect logic compatibility?

The 2.5 kΩ resistor limits input current to ≤1.0 mA at 3.75 V, enabling direct connection to 5 V microcontrollers (e.g., STM32, PIC, AVR) without buffer stages. It reduces loading versus ULN2065B (350 Ω) by over 70%, preserving signal integrity in high-fan-out systems.

What thermal considerations apply when using ULN2069B at full 1.5 A per channel?

At 1.5 A and 1.5 V V_CE(SAT), each channel dissipates 2.25 W. With four active channels, total dissipation reaches 9 W - exceeding the 4.3 W package limit. Therefore, only ≤2 channels should operate at full load simultaneously, or PCB copper area ≥4 cm² per GND pin must be used to maintain T_J < 150 °C.