Texas Instruments ULQ2003AD

Overview

ULQ2003AD from Texas Instruments is a high-voltage, high-current 7-channel NPN Darlington transistor array designed for inductive load switching. It delivers 500mA per channel, supports 50V collector-emitter voltage, integrates common-cathode clamp diodes, features 2.7kΩ input base resistors for direct TTL/5V CMOS compatibility, and operates across –40°C to +85°C ambient temperature - widely used in relay and stepper motor control circuits.

For engineers reviewing the ULQ2003AD datasheet, ULQ2003AD pinout, ULQ2003AD application, or ULQ2003AD equivalent, key selection considerations include per-channel saturation voltage (≤1.7V @ 350mA), input current requirements (0.35–1.45mA at 5–12V), flyback diode integration, thermal derating in SOIC-16 package, and functional distinction from ULN2003A (wider temp range) and ULQ2004A (higher input resistor).

Technical Context

The ULQ2003AD implements seven independent Darlington pairs with integrated 2.7kΩ series base resistors and shared COM cathode for inductive kickback suppression. Each channel functions as a grounded-emitter, open-collector switch capable of sinking up to 500mA while clamping reverse voltage to 50V via internal diodes.

It operates within a –40°C to +85°C ambient range and exhibits propagation delays of 1–10μs (tPLH/tPHL) under recommended conditions. Its electrical behavior is defined by VCE(sat) ≤1.7V at IC = 350mA and II = 500μA, and VI(on) ≤3V at IC = 300mA - confirming robust low-input-drive capability for microcontroller interfacing.

Key Specifications

Pinout & Package

ULQ2003AD is housed in a 16-pin SOIC (Small Outline Integrated Circuit) package measuring 9.90mm × 3.91mm, optimized for automated assembly and moderate-power PCB applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2003AD and ULQ2004AD, ULQ2003AD provides the widest operating temperature range (–40°C to +85°C) while retaining 3.3V/5V logic compatibility - making it optimal for industrial edge controllers where thermal margin and GPIO flexibility are both required.

Availability

ULQ2003AD is available at Aetrix Electronics and suitable for relay control, stepper motor actuation, and industrial display driver applications requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for ULQ2003AD 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 specializing in analog, embedded processing, and connectivity technologies, with decades of experience in industrial interface solutions.

The ULQ2003AD belongs to TI's ULx200x Darlington array product line, engineered specifically for robust, low-complexity interfacing between low-voltage logic and high-voltage/high-current loads in factory automation, building controls, and instrumentation systems.

FAQ

What is the maximum ambient temperature rating for ULQ2003AD?

The ULQ2003AD is rated for operation from –40°C to +85°C ambient temperature, exceeding the +70°C limit of the ULN2003AD variant. This extended range supports deployment in sealed industrial enclosures or outdoor control cabinets where passive heat buildup occurs. The ULQ2003AD maintains specified VCE(sat), propagation delay, and leakage parameters across this full range - confirmed in Section 5.1 of the SLRS027T datasheet.

Does ULQ2003AD require external flyback diodes when driving relays?

No, ULQ2003AD does not require external flyback diodes when driving relays. It integrates seven common-cathode clamp diodes connected between each collector output (Pins 10–16) and the COM pin (Pin 9). To enable flyback protection, the COM pin must be connected to the positive side of the relay coil supply. This internal structure eliminates seven discrete diodes, reducing BOM cost and PCB area - a key feature documented in Section 3 and Figure 7-2 of the datasheet.

Can ULQ2003AD interface directly with 3.3V microcontroller GPIOs?

Yes, ULQ2003AD can interface directly with 3.3V microcontroller GPIOs. Its 2.7kΩ internal input base resistors ensure sufficient base drive at 3.3V logic levels - verified by VI(on) ≤3V at IC = 300mA (Section 5.9). Unlike ULQ2004AD (10.5kΩ), ULQ2003AD avoids marginal turn-on behavior at 3.3V, making it ideal for modern low-voltage MCUs without level-shifting circuitry.

How many channels can be operated simultaneously at full 500mA load?

The number of simultaneously active channels at 500mA depends on thermal limits. In the SOIC-16 package (RθJA = 88.6°C/W), dissipating 0.6W per channel (500mA × 1.2V VCE(sat)) yields ~4.2W total - raising junction temperature by ~373°C above ambient. Therefore, continuous 500mA on all 7 channels is not feasible. Derating curves (Figure 5-4) show ≤2 channels at 100% duty cycle in SOIC at TA = 70°C. For full 7-channel use, reduce duty cycle or add heatsinking.

What is the purpose of the E pin (Pin 8) on ULQ2003AD?

The E pin (Pin 8) is the common emitter terminal for all seven Darlington pairs and must be connected to system ground. It serves as the reference node for input logic thresholds, output saturation voltage measurement, and internal current paths. Unlike the COM pin (which connects to clamp diode cathodes), E is electrically isolated from the diode network and forms the low-side return path for all switched loads - a requirement explicitly stated in Table 4-1 and Section 7.4.2 of the datasheet.