STMicroelectronics E-L6221AD

Overview

E-L6221AD from STMicroelectronics is a monolithic quad Darlington switch IC with four non-inverting logic-controlled outputs, common enable input, and integral fast recirculation diodes. It delivers up to 1.8 A per channel, supports 50 V output voltage, features TTL-compatible inputs, and exhibits ≤1.6 V collector-emitter saturation voltage at 1.8 A - enabling direct drive of solenoids, relays, and stepper motor windings in industrial control modules.

For engineers reviewing the E-L6221AD datasheet, E-L6221AD pinout, E-L6221AD application, or E-L6221AD equivalent, key selection criteria include per-channel current capability (1.8 A continuous), clamp diode forward voltage (≤2.0 V at 1.8 A), thermal resistance (R_{th j-amb} = 80 °C/W in SO16+2+2), and enable-controlled quad switching architecture for synchronized high-voltage load control.

Technical Context

The E-L6221AD integrates four independent Darlington transistor stages sharing a common emitter node and dual clamp diode networks (CLAMP A for channels 1–2, CLAMP B for channels 3–4). Each stage operates as an open-collector switch with TTL-level input thresholds (V_INL ≤ 0.8 V, V_INH ≥ 2.0 V) and enables simultaneous or selective activation via a single ENABLE pin.

Its electrical behavior is defined by low-saturation operation (V_CE(sat) = 1.0 V typ. at 0.6 A), fast switching (t_d(on) ≤ 2 μs, t_d(off) ≤ 5 μs into 10 Ω), and robust inductive load handling via integrated clamping - eliminating external flyback diodes for basic solenoid/relay driving.

Key Specifications

Pinout & Package

Package: SO16+2+2 (16-pin small outline with two additional exposed thermal pads - pin 17 and 18 are GND-connected thermal tabs).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ULN2803A and TBD62083AFG, the E-L6221AD uniquely combines 1.8 A per channel, 50 V rating, and dual-group clamp diodes in a thermally optimized SO16+2+2 - making it the only option among the three capable of driving 24 V solenoids at full rated current without external components or derating.

Availability

E-L6221AD is available at Aetrix Electronics and suitable for industrial PLC output modules, HVAC actuator controllers, and automated valve positioning systems requiring stable component supply and long-term obsolescence management.

Supply support for E-L6221AD 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, MEMS, and microcontroller technologies for industrial, automotive, and consumer markets.

The L6221 series belongs to ST's high-voltage power driver product line, designed specifically for ruggedized industrial switching applications where reliability, integrated protection, and simplified board layout are critical.

FAQ

What is the maximum safe operating temperature for the E-L6221AD junction?

The absolute maximum junction temperature is +150 °C, and the device is characterized over –40 to +150 °C. For continuous 1.8 A operation in SO16+2+2, ambient temperature must be limited to ≤70 °C with adequate PCB copper thermal relief (≥4 cm² 35 µm copper per GND pad) to maintain junction temperature within specification.

Can multiple E-L6221AD outputs be paralleled to increase current capacity?

Yes - the datasheet explicitly permits paralleling any number of inputs and outputs on the same device. Channels 1 & 4 or 2 & 3 are recommended due to closely matched turn-on/off delays and saturation voltages, enabling up to 3.6 A per pair while maintaining thermal balance and timing coherence.

Is an external Zener diode required when driving inductive loads?

A Zener diode in series with the internal clamp diodes is optional but recommended for faster current decay in high-energy inductive loads (e.g., large solenoids). The datasheet specifies V_Z + V_P < 35 V to avoid reverse second breakdown; typical implementation uses a 24 V Zener for 24 V systems.

Does the E-L6221AD support PWM operation, and what is its maximum frequency?

Yes - the E-L6221AD supports PWM with verified performance up to 50 kHz. At 1.8 A load, turn-on/turn-off delays (≤2 µs / ≤5 µs) and low V_CE(sat) ensure minimal switching loss; however, thermal management becomes critical above 20 kHz due to increased average power dissipation in the Darlington structure.