Skyworks Solutions Inc. SI8401AA-B-IS

Overview

SI8401AA-B-IS from Skyworks Solutions is a bidirectional I²C isolator with two galvanically isolated, open-drain SDA and SCL channels, supporting up to 1.7 MHz I²C clock rates, 35 mA sink capability per channel, and 2500 VRMS isolation rating in an SOIC-8 narrow-body package. It enables safe, low-latency communication between isolated power domains in industrial SMBus systems.

For engineers reviewing the SI8401AA-B-IS datasheet, SI8401AA-B-IS pinout, SI8401AA-B-IS application, or SI8401AA-B-IS equivalent, this device delivers verified bidirectional I²C isolation with hot-swap support, −40 to +125 °C operation, and UL/CSA/VDE safety certifications - critical for power supply monitoring, motor control interfaces, and PoE subsystems requiring robust data integrity across isolation barriers.

Technical Context

The SI8401AA-B-IS implements RF-based galvanic isolation using on/off keying modulation across a semiconductor barrier, eliminating startup initialization and enabling deterministic timing behavior. Its dual bidirectional I²C channels operate independently with side-specific under-voltage lockout (UVLO) thresholds (2.15–2.5 V) and fast start-up time (15–40 µs).

Each I²C channel features open-drain outputs with 35 mA sink current, logic-level compatibility across 3.0–5.5 V supplies, and differential input threshold margins (I²CΔV ≥ 135 mV on Side A) to prevent bus latch-up. Propagation delay is 9.0–29 ns (rising/falling, 3.3/5 V), with pulse width distortion ≤15 ns.

Key Specifications

Pinout & Package

SI8401AA-B-IS is housed in an 8-pin narrow-body SOIC package (SOIC-8 NB) with creepage/clearance of 4.01 mm / 4.9 mm and 2.54 mm pitch. Pin 1 is marked with a dot; pins 1–4 connect to Side A (primary domain), pins 5–8 to Side B (isolated domain).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADUM1250ARZ and ISO1540DR, SI8401AA-B-IS uniquely supports 1.7 MHz I²C operation with side-specific UVLO, lower propagation delay (9–29 ns), and guaranteed hot-swap resilience - making it optimal for high-speed, safety-critical industrial and PoE applications where timing margin and power sequencing robustness are non-negotiable.

Availability

SI8401AA-B-IS is available at Aetrix Electronics and suitable for industrial motor control, isolated power supply monitoring, and Power over Ethernet applications requiring stable component supply, long-term lifecycle assurance, and certified 2500 VRMS isolation.

Supply support for SI8401AA-B-IS 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

Skyworks Solutions is a global semiconductor company specializing in analog and mixed-signal connectivity solutions, with leadership in RF, timing, and isolation technologies.

The Si840x family was designed specifically for robust, high-speed I²C and SMBus isolation in harsh industrial, automotive, and power infrastructure environments - replacing optocouplers with RF-based reliability and precision.

FAQ

What is the maximum I²C clock frequency supported by the SI8401AA-B-IS?

The SI8401AA-B-IS supports I²C clock frequencies up to 1.7 MHz, as confirmed in Table 6 of the Skyworks datasheet Rev. 1.6. This enables fast-mode plus operation and reduces transaction time for sensor polling or power telemetry in systems like motor drives and PoE controllers. The SI8401AA-B-IS achieves this with propagation delays as low as 9.0 ns (falling edge, 3.3 V), ensuring timing compliance even with bus capacitance up to 400 pF.

Does the SI8401AA-B-IS require external components for basic I²C isolation functionality?

Yes, the SI8401AA-B-IS requires external 0.1 µF and 1 µF bypass capacitors on both VDDA and VDDB pins, placed as close as possible to the package per Section 3.3.1 of the datasheet. Pull-up resistors on SDA/SCL lines are also mandatory per I²C specification. No external level shifters or termination resistors are needed for standard I²C operation, but series resistors (50–300 Ω) are recommended in noisy environments to protect inputs/outputs from voltage spikes exceeding 6 V absolute maximum rating.

How does the SI8401AA-B-IS handle power loss on one side during operation?

When power is lost on one side (e.g., VDDA = 0 V), the SI8401AA-B-IS places the corresponding I²C outputs (SDAA, SCLA) into high-impedance state to prevent back-powering or bus contention, as specified in Table 12. Side B remains fully operational if VDDB is valid. Independent UVLO circuits monitor each supply, and outputs resume normal operation within 1 µs after power restoration - preserving system-level hot-swap capability without firmware intervention.

Is the SI8401AA-B-IS certified for reinforced insulation in safety-critical systems?

Yes, the SI8401AA-B-IS is certified for reinforced insulation per UL 1577 (2500 VRMS), CSA Component Notice 5A (IEC 60950-1/61010-1), and VDE 0884-2 (IEC 60747-5-2). These certifications cover working voltages up to 560 Vpeak (basic) and 300 VRMS (reinforced), validated by production testing at 3000 VRMS for 1 second. The SOIC-8 narrow-body package provides 4.9 mm clearance and 4.01 mm creepage, satisfying end-equipment standards including IEC 61000-4-5 and EN 61800-5-1.

Can the SI8401AA-B-IS replace optocoupler-based I²C isolators without PCB layout changes?

Yes, the SI8401AA-B-IS uses a standard SOIC-8 narrow-body footprint (5.0 × 6.2 mm, 2.54 mm pitch) identical to many optocoupler-based I²C isolators. However, layout best practices differ: the SI8401AA-B-IS requires separate ground planes for AGND and BGND with no copper bridges across the isolation barrier, and minimum 8 mm spacing between high-voltage and SELV traces per IEC 60664-1. Thermal vias under exposed pads are not applicable, as the package has no thermal pad.