Analog Devices Inc. AD261BND-2

Overview

AD261BND-2 from Analog Devices is a high-speed logic isolator with 2 input / 3 output unidirectional channel configuration, 3.5 kV_rms isolation rating, 20 MHz minimum signal bandwidth, and 14 ns typical propagation delay. It replaces up to five optocouplers in industrial I/O modules requiring precise PWM signal isolation and field/system side decoupling.

For engineers reviewing the AD261BND-2 datasheet, AD261BND-2 pinout, AD261BND-2 application, or AD261BND-2 equivalent, this page delivers verified specifications, exact pin functions for the ND-22A DIP-22 package, real-world use cases in PLC analog I/O and motor drive controls, and two validated alternative isolators with documented functional trade-offs.

Technical Context

The AD261BND-2 implements five isolated HCMOS-compatible logic channels using capacitive isolation with set-hi/set-lo data encoding across a 3.5 kV_rms tested barrier. Each channel features a Schmitt-trigger input (2.0–4.2 V threshold range) and three-state output controlled by ENABLESYS/ENABLEFLD pins.

It supports continuous background update (every ~5 µs) to guarantee valid output states within 12 µs after power-up or fault recovery, and maintains ±1 ns edge symmetry error between rising/falling transitions - critical for accurate time-based signal isolation such as PWM and encoder timing.

Key Specifications

Pinout & Package

AD261BND-2 uses the 22-pin plastic DIP package (ND-22A) with 18 mm creepage spacing between system and field sides, supporting CSA/IS and IEC 750 V mains isolation requirements. Pin 1 is marked with a notch; pins 9–14 are not present.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-speed logic isolation applications.

Compared with Si8623BD-B-IS and ISO6721DR, the AD261BND-2 uniquely combines dual independent enable pins, guaranteed 12 µs output validity after power-up, and fixed 2-in/3-out topology in a through-hole DIP package - making it optimal for legacy industrial designs requiring robust, maintenance-friendly isolation with deterministic timing behavior.

Availability

AD261BND-2 is available at Aetrix Electronics and suitable for PLC analog input cards, IGBT motor drive interfaces, and industrial data acquisition hubs requiring stable component supply, long-term lifecycle support, and traceable sourcing for safety-critical deployments.

Supply support for AD261BND-2 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

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets since 1965.

The AD261 product line was designed specifically for high-reliability industrial digital isolation - delivering optocoupler replacement with superior speed, timing accuracy, and transient immunity in harsh electromagnetic environments.

FAQ

What is the isolation voltage rating of the AD261BND-2?

The AD261BND-2 is rated for 3.5 kV_rms isolation test voltage and has an operating isolation voltage of 1.25 kV_rms. This rating is 100% production-tested per Analog Devices' standard method and supports UL1950, IEC950, and EN60950 certification. The AD261BND-2 achieves this with >18 mm creepage distance in its ND-22A package, enabling safe operation in 750 V mains-referenced field circuits.

How does the AD261BND-2 handle power-up and fault recovery?

The AD261BND-2 guarantees valid output states within 12 µs after power-up or fault recovery due to its continuous background update circuit, which interrogates inputs every ~5 µs. Unlike optocouplers or basic digital isolators, the AD261BND-2 does not require external reset signals - its internal logic ensures F0–F2 reflect true S0–S1 states without delay or ambiguity, critical for fail-safe I/O in industrial controllers.

Can unused pins on the AD261BND-2 be left floating?

No - unused pins on the AD261BND-2 (S2–S4 and F3–F4) must be tied either high or low and never left floating. The datasheet explicitly warns that floating inputs can cause unpredictable behavior, increased power consumption, or susceptibility to noise. This requirement applies regardless of whether the pin is physically present (pins 1–5 and 18–22) or absent (pins 9–14).

What is the function of ENABLESYS and ENABLEFLD on the AD261BND-2?

ENABLESYS (pin 6) and ENABLEFLD (pin 17) are active-low enable pins that place all outputs on their respective sides into high-impedance three-state mode. For AD261BND-2, ENABLEFLD controls F0–F2 outputs, allowing presetting of logic levels via pull-up/down resistors at power-up; ENABLESYS is reserved for future expansion or multiplexing but has no effect on outputs in this variant.

Does the AD261BND-2 support bidirectional communication?

No - the AD261BND-2 implements strictly unidirectional logic channels: S0 and S1 are inputs only, F0–F2 are outputs only. Directionality is hardwired per model; there is no software or hardware mechanism to reverse signal flow. For bidirectional isolation, multiple AD261 devices or alternate solutions like the ADuM1201 would be required.