Allegro MicroSystems UDN2982A

Overview

UDN2982A from Allegro MicroSystems is an 8-channel high-side source driver IC designed for interfacing 5 V logic (TTL, CMOS, DTL) with inductive or resistive loads up to 50 V and –500 mA per channel. It integrates input current-limiting resistors and output clamp diodes, features active-high logic control, and operates from –20°C to +85°C ambient.

For engineers reviewing the UDN2982A datasheet, UDN2982A pinout, UDN2982A application, or UDN2982A equivalent, key selection criteria include its 20-pin SOICW package, 50 V output breakdown voltage, 1.6–2.0 V V_CE(SAT) at load currents up to –350 mA, transient-protected outputs, and compatibility with relay, solenoid, LED, and stepper motor drive circuits.

Technical Context

The UDN2982A implements eight independent NPN Darlington source drivers with integrated base resistors and output flyback diodes. Each channel delivers up to –500 mA output current with V_CE(SAT) of 1.6 V (typ.) at –100 mA and 1.8 V (typ.) at –350 mA.

It supports high-side switching with separate logic (V_IN) and load (V_S) grounds, enabling galvanic isolation between control and power domains. Input compatibility spans TTL, Schottky TTL, DTL, and 5 V CMOS, with input current ranging from 140 µA (at 2.4 V) to 1.93 mA (at 12 V).

Key Specifications

Pinout & Package

UDN2982A uses a 20-pin wide-body SOIC (SOICW) package with 100% matte-tin leadframe plating and Pb-free construction. Pinout matches discontinued 18-pin variants electrically (pins 1–9 and 12–20 correspond to pins 1–18), with NC pins 10 and 11 added for mechanical stability and thermal improvement.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-side source driver applications.

Compared with A2982SLWTR-T, UDN2982A shares identical functionality but may differ in packaging format or test screening; compared with ULN2803A, UDN2982A provides true high-side sourcing with built-in resistors and separate grounds-critical for isolated load control where load return cannot be tied to logic ground.

Availability

UDN2982A is available at Aetrix Electronics and suitable for industrial automation, electromechanical actuation, LED signage, and embedded motion control applications requiring stable component supply and long-term manufacturability.

Supply support for UDN2982A 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

Allegro MicroSystems is a U.S.-based designer and manufacturer of high-performance magnetic sensing and power IC solutions, headquartered in Worcester, Massachusetts.

The UDN2982A belongs to Allegro's high-side driver product line, engineered specifically for robust, low-component-count interface between logic-level controllers and industrial-grade inductive or resistive loads.

FAQ

What is the maximum continuous output current per channel for UDN2982A?

The UDN2982A supports –500 mA continuous output current per channel under specified thermal conditions (TA ≤ 85°C, single channel active). Derating applies when multiple channels conduct simultaneously - e.g., at 50°C ambient, maximum recommended current drops to ~350 mA per channel with all eight outputs active, per the allowable peak collector current graph in the datasheet. Always verify junction temperature using R_JA = 90°C/W.

Does UDN2982A require external flyback diodes when driving relays?

No, UDN2982A does not require external flyback diodes when driving relays. Each output includes an integrated clamp diode rated for 50 μA reverse leakage and capable of handling typical inductive kick energy from 24 V relays. The diode anode connects internally to V_S, cathode to OUTx - providing automatic suppression of negative voltage transients during turn-off.

Can UDN2982A be used with 3.3 V logic inputs?

UDN2982A is optimized for 5 V logic families (TTL, CMOS, DTL) and specifies guaranteed operation with VIN ≥ 2.4 V for turn-on. While 3.3 V logic may activate the inputs in many cases, it falls below the tested minimum threshold and risks marginal or inconsistent switching - especially over temperature or process variation. For reliable 3.3 V compatibility, use a level-shifter or select a driver explicitly characterized for 3.3 V input logic.

What is the purpose of pins 10 and 11 on the UDN2982A 20-pin SOICW package?

Pins 10 and 11 on the UDN2982A are No-Connect (NC) terminals. They were added to the 20-pin SOICW package to improve mechanical stability and thermal performance versus the legacy 18-pin SOIC version. These pins are electrically isolated and must remain unconnected; they do not affect functionality or pin compatibility with earlier variants.

How does UDN2982A handle unused inputs?

All unused inputs on UDN2982A must be connected to GND to prevent floating states that could cause unintended output activation or increased power consumption. Allegro recommends using ~10 kΩ pull-down resistors on any inputs that may float during power-up or system reset sequences. Leaving inputs open violates the Absolute Maximum Ratings and may result in unpredictable behavior or accelerated device degradation.