Skyworks Solutions Inc. SI8401AB-B-IS

Overview

SI8401AB-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 bus frequency, 2500 VRMS isolation rating, and operation across –40 to +125 °C. It delivers 35 mA sink capability per I²C channel, uses RF-based isolation for low propagation delay (≤29 ns), and targets hot-swap I²C/SMBus interfaces in power supply monitoring systems.

For engineers reviewing the SI8401AB-B-IS datasheet, SI8401AB-B-IS pinout, SI8401AB-B-IS application, or SI8401AB-B-IS equivalent, this page provides verified functional identity, validated SOIC-8 narrow-body package mapping, confirmed bidirectional I²C timing specs, safety certification details (UL 1577, VDE 0884-2, CSA 5A), and real-world design context for isolated serial communication in high-reliability embedded systems.

Technical Context

The SI8401AB-B-IS implements RF-based on-off keying modulation across a semiconductor isolation barrier-eliminating startup initialization and enabling robust noise immunity (25 kV/µs CMTI) without external clocking. Its dual-channel architecture supports independent bidirectional SDA/SCL isolation with side-specific under-voltage lockout (UVLO+ = 2.3 V, hysteresis = 75 mV).

Each side features dedicated 3.0–5.5 V supplies (AVDD/BVDD), internal protection against unpowered insertion, and logic-level compatibility with standard I²C drivers: Side A thresholds (VIL = 0.45 V, VIH = 0.78 V), Side B output drive (≤400 mV at 35 mA), and guaranteed I²C ΔV margin (≥175 mV) to prevent bus latch-up.

Key Specifications

Pinout & Package

SI8401AB-B-IS is housed in an 8-pin narrow-body SOIC package (SOIC-8 NB) with 4.9 mm creepage/clearance, RoHS-compliant lead finish, and surface-mount land pattern per Skyworks document #27.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADUM1250ARZ and ISO1540DR, SI8401AB-B-IS uniquely combines 1.7 MHz I²C support, native open-drain topology, VDE-certified reinforced insulation, and hot-swap protection-making it the only option among the three qualified for high-speed, safety-critical SMBus implementations in PoE and motor control.

Availability

SI8401AB-B-IS is available at Aetrix Electronics and suitable for industrial motor control, Power over Ethernet (PoE), and intelligent power system designs requiring stable component supply, long-term lifecycle assurance, and certified 2500 VRMS isolation performance.

Supply support for SI8401AB-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 for communications, automotive, and industrial markets.

The Si840x family was engineered specifically for galvanic isolation of I²C and SMBus interfaces-replacing optocouplers with RF-based architecture to deliver lower power, smaller footprint, higher speed, and longer reliability in harsh environments.

FAQ

What is the maximum I²C bus frequency supported by SI8401AB-B-IS?

The SI8401AB-B-IS supports a maximum I²C bus frequency of 1.7 MHz, enabling compliance with fast-mode-plus (Fm+) specifications. This is verified across the full operating temperature range (–40 to +125 °C) and supply voltage range (3.0–5.5 V). The timing specification is measured with defined test conditions (R1 = 806 Ω, R2 = 499 Ω, no bus capacitance) and reflects worst-case propagation delay (≤29 ns A→B rising at 5 V), ensuring robust timing margin in real-world designs using SI8401AB-B-IS.

Does SI8401AB-B-IS require external pull-up resistors on the I²C bus lines?

Yes, SI8401AB-B-IS requires external pull-up resistors on both ASDA/ASCL and BSDA/BSCL lines because its I²C channels feature open-drain outputs. Standard values (e.g., 1.8 kΩ at 3.3 V) are compatible with its 35 mA sink capability on Side B. The device does not integrate pull-ups; omitting them will prevent proper I²C logic high states and cause bus failure. SI8401AB-B-IS datasheet Figure 2 confirms this configuration in the recommended test circuit.

What safety certifications apply to SI8401AB-B-IS?

SI8401AB-B-IS holds UL 1577 (2500 VRMS), VDE 0884-2 (IEC 60747-5-2), and CSA Component Acceptance Notice 5A certifications. These cover reinforced insulation for working voltages up to 560 Vpeak (VDE) and 300 VRMS (CSA/UL), with production-tested isolation at 3000 VRMS for 1 second. Certification files are E257455 (UL), 5006301-4880-0001 (VDE), and 232873 (CSA), all referencing the exact SI8401AB-B-IS variant.

Can SI8401AB-B-IS operate with different supply voltages on Side A and Side B?

Yes, SI8401AB-B-IS supports independent 3.0–5.5 V supplies on AVDD and BVDD, enabling true level-shifting between mismatched voltage domains (e.g., 3.3 V MCU ↔ 5 V power controller). Each side has its own UVLO circuit (2.3 V turn-on, 75 mV hysteresis), so asymmetric power sequencing is tolerated. This capability is explicitly validated in Table 2 (power characteristics) and Section 3.2 (Under Voltage Lockout) of the SI8401AB-B-IS datasheet.

Is SI8401AB-B-IS suitable for hot-swap applications?

Yes, SI8401AB-B-IS includes integrated protection circuits that prevent data errors when inserted into a powered system-an explicit design requirement stated in the product description. This is achieved via internal clamping and state-holding logic that maintains bus integrity during partial power-up. The feature is validated in Table 12 (Si84xx Operation Table) and referenced in the "Features" section of the SI8401AB-B-IS datasheet, confirming safe hot-swap capability without external circuitry.