Analog Devices Inc./Maxim Integrated ADUM1255ASA+T

Overview

ADUM1255ASA+T from Analog Devices is a dual-channel I²C isolator with unidirectional SCL and bidirectional SDA, designed for galvanically isolated I²C/SMBus interfaces in harsh environments. It supports 2.25V–5.5V supplies on both sides, operates up to 2 MHz, delivers side-1 VOL ≤ 0.69 V and side-2 VOL ≤ 0.4 V, and enables hot-swap connection on side 2 during bus idle or STOP condition - critical for battery management and PoE systems.

For engineers reviewing the ADUM1255ASA+T datasheet, ADUM1255ASA+T pinout, ADUM1255ASA+T application, or ADUM1255ASA+T equivalent, key selection criteria include its open-drain SDA/SCL channel architecture, side-specific logic-low regulation (0.64 V on side 1), 8-pin narrow SOIC package with 4 mm creepage/clearance, and reinforced isolation ratings (445 VRMS working voltage, 3000 VRMS withstand).

Technical Context

The ADUM1255ASA+T implements two independent isolation channels: SCL1→SCL2 is strictly unidirectional (input on side 1, open-drain output on side 2), while SDA1↔SDA2 is fully bidirectional using internal encode/decode logic to prevent bus latch-up. Side 1 employs regulated low-voltage buffers (VOL = 0.64 V) with ≥50 mV margin below VIH to avoid false triggering; side 2 uses conventional open-drain drivers with higher sink capability (50 mA).

Hot-swap operation is enabled by precharging side-2 bus pins to 0.3×VDD2 via 140 kΩ Thevenin impedance, followed by idle-bus detection (75 µs timeout) and controlled connection only after STOP or sustained high state. This prevents data corruption during live insertion of isolated peripherals in motor control or BMS subsystems.

Key Specifications

Pinout & Package

ADUM1255ASA+T is housed in an 8-pin narrow-body SOIC package (Outline 21-0041) with 4 mm creepage and clearance, RoHS-compliant, moisture sensitivity level 3.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I²C isolator applications.

Compared with ADUM1250ARZ and ISO1540DR, ADUM1255ASA+T uniquely combines side-1 logic-low regulation (0.64 V), integrated hot-swap precharge, and narrow-SOIC footprint - making it the only option that simultaneously satisfies stringent VOL compliance, live-insertion safety, and board-space constraints in high-density industrial designs.

Availability

ADUM1255ASA+T is available at Aetrix Electronics and suitable for battery management systems, industrial motor control, and Power over Ethernet (PoE) applications requiring stable component supply, long-term lifecycle assurance, and guaranteed traceable sourcing.

Supply support for ADUM1255ASA+T 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, Inc. 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 ADUM1255ASA+T belongs to Analog Devices' iCoupler® digital isolation product line, engineered specifically for robust, low-latency, and standards-compliant isolation of I²C, SMBus, and other bidirectional serial buses in safety-critical and noise-prone systems.

FAQ

What is the maximum SCL frequency supported by the ADUM1255ASA+T?

The ADUM1255ASA+T supports a maximum SCL clock frequency of 2 MHz, meeting I²C fast-mode Plus specifications. This is verified across the full operating temperature range (−40°C to +125°C) and supply range (2.25 V to 5.5 V on both sides), with propagation delays (tPLH12/tPHL12) specified up to 133.3 ns at 5.5 V.

Does the ADUM1255ASA+T support clock stretching on side 2?

No, the ADUM1255ASA+T does not support clock stretching on side 2. SCL1 is a unidirectional input, and SCL2 is a strictly open-drain output driven only by SCL1. Any clock stretching must originate on side 1; side-2 peripherals cannot hold SCL2 low to extend the clock cycle.

What is the purpose of the regulated 0.64 V output low voltage on side 1 of the ADUM1255ASA+T?

The regulated 0.64 V VOL on side 1 ensures ≥45 mV margin below the minimum VIH1 threshold (0.52 V), preventing bus latch-up when interfacing with I²C slaves that have tight input threshold tolerances. This design eliminates false ACK/NACK generation and guarantees interoperability across diverse I²C device families.

Can the ADUM1255ASA+T be used with different supply voltages on side 1 and side 2?

Yes, ADUM1255ASA+T supports independent supplies: VDD1 and VDD2 each operate from 2.25 V to 5.5 V. This enables true level-shifting - for example, 3.3 V MCU (side 1) communicating with 5 V sensor (side 2) - without external level translators or shared supply rails.

What isolation certifications apply to the ADUM1255ASA+T in its narrow SOIC package?

The ADUM1255ASA+T in narrow SOIC (21-0041) is pending UL 1577 (3000 VRMS, 1 min), IEC 60747-17 (reinforced, 630 VPEAK VIORM), IEC/EN/CSA 62368-1, and IEC/EN/CSA 61010-1 certification. Its 445 VRMS working voltage and 4 mm creepage meet basic insulation requirements for industrial and PoE applications up to 300 VRMS mains.