Skyworks Solutions Inc. SI8405AB-B-IS1R

Overview

SI8405AB-B-IS1R from Skyworks Solutions is a 16-pin SOIC narrow-body bidirectional I²C isolator with two unidirectional digital channels, supporting up to 1.7 MHz I²C clock rate, 2500 VRMS isolation, and 3.0–5.5 V dual supply operation. It provides galvanic isolation for SDA/SCL lines plus two additional system signals (e.g., interrupt or reset) in motor control, PoE, and intelligent power systems.

For engineers reviewing the SI8405AB-B-IS1R datasheet, SI8405AB-B-IS1R pinout, SI8405AB-B-IS1R application, or SI8405AB-B-IS1R equivalent, this page delivers verified electrical specs, safety certifications (UL/CSA/VDE), timing performance (≤29 ns propagation delay), and real-world design context for I²C bus isolation in high-noise industrial environments.

Technical Context

The SI8405AB-B-IS1R implements RF-based galvanic isolation using on/off keying modulation across a semiconductor barrier-enabling robust noise immunity (25 kV/µs CMTI), no startup initialization, and stable operation over –40 to +125 °C. Its architecture separates bidirectional I²C channels (SDA/SCL) from two independent unidirectional CMOS-compatible digital channels.

Each side features independent under-voltage lockout (UVLO+ = 2.3 V, hysteresis = 75 mV), hot-swap capability, and open-drain I²C outputs with 35 mA sink current on Side B. Non-I²C channels deliver 10 Mbps data rate, 40 ns minimum pulse width, and 85 Ω nominal output impedance for controlled-impedance PCB routing.

Key Specifications

Pinout & Package

SI8405AB-B-IS1R is housed in a 16-pin narrow-body SOIC package (7.5 mm × 10.3 mm, 1.27 mm pitch) with creepage/clearance ≥4.01 mm and 2.5 kVRMS working voltage rating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADUM1250ARZ and ISO1540DR, SI8405AB-B-IS1R uniquely integrates bidirectional I²C isolation with two unidirectional channels in a single 16-pin SOIC package-reducing component count, PCB area, and interconnect complexity in systems requiring coordinated isolated signaling beyond the I²C bus.

Availability

SI8405AB-B-IS1R is available at Aetrix Electronics and suitable for industrial motor control, Power over Ethernet (PoE), and intelligent power systems requiring stable component supply, long-term lifecycle support, and certified 2500 VRMS isolation.

Supply support for SI8405AB-B-IS1R 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 leader in analog and mixed-signal semiconductors, specializing in RF, timing, and isolation technologies for high-reliability communications and power systems.

The Si840x family was designed specifically for robust, low-latency galvanic isolation of I²C and SMBus interfaces in harsh industrial, automotive, and PoE environments-leveraging proprietary RF isolation to replace aging optocoupler solutions.

FAQ

What is the maximum I²C clock frequency supported by the SI8405AB-B-IS1R?

The SI8405AB-B-IS1R supports a maximum I²C clock frequency of 1.7 MHz, enabling compatibility with fast-mode Plus I²C devices while maintaining full protocol transparency. This specification is validated across the full operating temperature range (–40 to +125 °C) and supply voltage range (3.0–5.5 V). The SI8405AB-B-IS1R achieves this performance with propagation delays as low as 20 ns (typical) on critical I²C paths, making it suitable for time-critical sensor and power management interfaces.

Does the SI8405AB-B-IS1R require external pull-up resistors on its I²C lines?

Yes, the SI8405AB-B-IS1R requires external pull-up resistors on both SDA and SCL lines on each side (Side A and Side B), as its I²C outputs are open-drain. Typical values range from 1.8 kΩ to 4.7 kΩ depending on bus capacitance and speed requirements. The device itself provides 35 mA sink capability on Side B and 15 mA on Side A, ensuring reliable low-level assertion even with standard pull-up configurations. No internal pull-ups are present.

How does the SI8405AB-B-IS1R behave when one side loses power?

When either AVDD or BVDD falls below the UVLO threshold (2.3 V), that side enters under-voltage lockout: non-I²C outputs go low, and I²C outputs go high-impedance (Hi-Z) to prevent bus contention. The SI8405AB-B-IS1R remains electrically safe and will resume normal operation within 40 µs after supply recovery. This behavior is independently managed per side, allowing graceful degradation in partial-power-loss scenarios common in PoE and motor control systems.

What safety certifications apply to the SI8405AB-B-IS1R?

The SI8405AB-B-IS1R is certified to UL 1577 (2500 VRMS, 1 min), CSA Component Acceptance Notice 5A (IEC 60950-1/61010-1), and VDE IEC 60747-5-2 (560 Vpeak working voltage). These certifications cover reinforced insulation for industrial and commercial end-equipment. The device is production-tested to 3000 VRMS for 1 second and meets creepage/clearance requirements of ≥4.01 mm in its SOIC-16 narrow-body package.

Can the unidirectional channels of the SI8405AB-B-IS1R be used for general-purpose isolated GPIO?

Yes, the two unidirectional channels in the SI8405AB-B-IS1R are fully CMOS-compatible with 10 Mbps data rate, 40 ns minimum pulse width, and 85 Ω nominal output impedance-making them suitable for isolated GPIO, interrupt, reset, enable, or status signaling. They operate independently of the I²C channels and support standard logic thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) across the full supply and temperature range. Each channel can be configured as input or output via external connection.