STMicroelectronics ULN2065B

Overview

ULN2065B from STMicroelectronics is a quad NPN Darlington transistor array in PowerDIP-16 package, designed for high-voltage, high-current logic-to-load interfacing. Each channel delivers 1.5 A output current with 80 V breakdown voltage, 35 V sustaining voltage, and integrated clamp diodes-enabling direct drive of relays, solenoids, and lamps in industrial control systems.

For engineers reviewing the ULN2065B datasheet, ULN2065B pinout, ULN2065B application, or ULN2065B equivalent, key selection criteria include output current capability per channel, input compatibility with 5 V TTL/CMOS logic, thermal derating at elevated ambient temperatures, and clamp diode forward voltage under 1.5 A load current.

Technical Context

The ULN2065B integrates four independent Darlington pairs with base resistors (R_IN = 350 Ω) and built-in flyback diodes connected anode-to-emitter. It operates with input logic referenced to ground and requires no external biasing-simplifying interface design for microcontroller GPIOs driving inductive loads.

Each Darlington stage exhibits low saturation voltage (1.3 V at I_C = 1 A), enabling efficient power delivery while maintaining thermal stability up to 85 °C ambient. The device's 4.3 W power dissipation rating at T_PINS = 90 °C supports PCB copper-area heatsinking per Figure 14 of the datasheet.

Key Specifications

Pinout & Package

ULN2065B uses a 16-pin PowerDIP (dual in-line package) with 0.3-inch body width, 2.54 mm pin pitch, and GND pins (pins 8 and 16) thermally optimized for PCB copper-area heatsinking per ST's mounting instructions.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2067B and ULN2069B, the ULN2065B offers optimal balance of 5 V logic compatibility, thermal robustness via dual GND pins, and cost efficiency for mainstream industrial control-making it the default choice unless higher input voltage or ultra-low input loading is required.

Availability

ULN2065B is available at Aetrix Electronics and suitable for industrial relay control, stepper motor phase driving, LED signage array switching, and automated test equipment load switching requiring stable component supply across extended production lifecycles.

Supply support for ULN2065B 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, mixed-signal, power, and microcontroller products for industrial, automotive, and consumer markets.

The ULN2065B belongs to ST's high-voltage Darlington array product line, engineered specifically for robust logic-to-load interfacing in harsh industrial environments where reliability, thermal resilience, and integrated protection are critical.

FAQ

What is the maximum continuous output current per channel for ULN2065B?

The ULN2065B is rated for 1.5 A continuous output current per channel at T_AMB ≤ 70 °C with proper PCB heatsinking. At 85 °C ambient, derating applies-maximum current drops to approximately 1.1 A based on its 4.3 W power dissipation limit and thermal resistance profile.

Does ULN2065B require external flyback diodes when driving relays?

No. The ULN2065B includes integral clamp diodes connected from each output to the common emitter (GND), which suppress inductive kickback from relay coils and solenoids. External diodes are unnecessary unless extreme dv/dt or EMI requirements demand additional filtering.

Can ULN2065B be used with 3.3 V logic microcontrollers?

Yes-its input threshold is compatible with 3.3 V logic when driven with sufficient current. At V_I = 2.4 V, input current is ~3.3 mA (per datasheet Table 3), well within typical MCU GPIO sink capability. For marginal cases, verify that the MCU can sustain ≥3 mA per channel at 2.4 V.

How should the GND pins be connected for optimal thermal performance?

Both GND pins (pins 8 and 16) must be soldered to a large, low-thermal-resistance copper area on the PCB, as shown in Figure 14 of the datasheet. This reduces R_thJA significantly-enabling full 1.5 A per channel operation at 70 °C ambient. Connecting only one GND pin compromises thermal safety margin.