Texas Instruments ULN2803ADWRG4

Overview

ULN2803ADWRG4 from Texas Instruments is an 8-channel NPN Darlington transistor array optimized for high-voltage (50 V), high-current (500 mA per channel) sink switching of inductive and resistive loads. It integrates internal 2.7-kΩ base resistors and common-cathode clamp diodes, enabling direct interface with 3.3 V or 5 V TTL/CMOS logic without external components. It is widely deployed in relay drivers, LED displays, and solenoid control circuits.

For engineers reviewing the ULN2803ADWRG4 datasheet, ULN2803ADWRG4 pinout, ULN2803ADWRG4 application, or ULN2803ADWRG4 equivalent, key selection considerations include per-channel saturation voltage (1.3 V max at 200 mA), input compatibility with standard logic families, thermal derating at elevated ambient temperatures, and COM pin configuration for flyback protection in inductive switching.

Technical Context

The ULN2803ADWRG4 implements eight independent Darlington pairs-each formed by cascaded NPN transistors-to achieve current gain up to 10,000 A/A. Each channel includes a dedicated 2.7-kΩ series input resistor and integrated clamp diode tied to the COM terminal.

It operates in two primary functional modes: inductive load drive (COM connected to coil supply) and resistive load drive (COM floating, requiring external pull-up). Input logic thresholds are compatible with both 3.3 V and 5 V CMOS/TTL, with guaranteed turn-on at VI ≥ 2.7 V and off-state leakage < 65 μA at 70°C.

Key Specifications

Pinout & Package

ULN2803ADWRG4 is housed in an 18-pin SOIC (DW) package measuring 11.50 mm × 7.50 mm, with standard JEDEC MS-013 footprint and moisture sensitivity level (MSL) 2 (260°C, 1 year).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2803ADR and STMicro ULN2803A, the ULN2803ADWRG4 offers marginally lower saturation voltage and superior thermal resistance in the same SOIC-DW package, making it optimal for high-density industrial control boards requiring sustained multi-channel sinking capability.

Availability

ULN2803ADWRG4 is available at Aetrix Electronics and suitable for relay drivers, lamp drivers, LED display interfaces, and solenoid control applications requiring stable component supply across extended production lifecycles.

Supply support for ULN2803ADWRG4 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.

The ULN2803ADWRG4 belongs to TI's legacy power interface portfolio, designed specifically for robust, low-cost, high-current logic-level interfacing between microcontrollers and electromechanical loads.

FAQ

What is the maximum continuous sink current per channel for ULN2803ADWRG4?

The ULN2803ADWRG4 supports 500 mA maximum collector current per channel under recommended operating conditions (T_J ≤ 125°C). At 200 mA, V_CE(sat) is guaranteed ≤1.3 V. Derating is required above +70°C ambient; consult Figure 2 in TI's SLRS049G datasheet for thermal curves. ULN2803ADWRG4 must be used with adequate copper pour and airflow in multi-channel high-current configurations.

Can ULN2803ADWRG4 drive 24 V relays directly?

Yes - ULN2803ADWRG4 supports output voltages up to 50 V, making it fully compatible with 24 V DC relays. The COM pin must be connected to the relay coil's positive supply rail to activate internal clamp diodes. With a 24 V supply and 200 Ω coil resistance, ULN2803ADWRG4 delivers ~120 mA per channel while maintaining V_CE(sat) < 1.2 V, ensuring reliable switching without external flyback components.

Is ULN2803ADWRG4 compatible with 3.3 V microcontrollers?

Yes - ULN2803ADWRG4 features built-in 2.7-kΩ base resistors that ensure full turn-on with 3.3 V logic inputs. At V_I = 3.3 V, input current is ~1.2 mA per channel, sufficient to saturate the Darlington pair even at elevated temperatures. No level-shifter or external resistor is needed, simplifying interface design for modern low-voltage MCUs.

How should the COM pin be connected for inductive load operation?

For inductive loads (relays, solenoids, motors), connect the COM pin directly to the positive supply rail of the load. This ties the cathodes of all internal clamp diodes to the supply, allowing flyback current to recirculate safely when the Darlington turns off. Leaving COM unconnected or grounding it disables clamp functionality and risks voltage spikes exceeding 50 V, potentially damaging ULN2803ADWRG4 or upstream circuitry.

What is the thermal resistance (R_θJA) of ULN2803ADWRG4 in SOIC-DW package?

The ULN2803ADWRG4 in SOIC-DW (18-pin) package has a junction-to-ambient thermal resistance (R_θJA) of 66.4°C/W, as specified in Section 7.4 of TI's SLRS049G datasheet. This value assumes standard JEDEC 2S2P test board conditions. Real-world performance improves with ≥1 in² copper pour under the exposed pad (if present) and forced airflow; for 8-channel 200 mA operation, keep ambient below +75°C to maintain T_J < 125°C.