Skyworks Solutions Inc. SI8400AB-A-ISR

Overview

SI8400AB-A-ISR from Skyworks Solutions is a bidirectional I²C isolator with two unidirectional digital channels, designed for galvanic isolation of I²C/SMBus buses in high-noise or safety-critical systems. It delivers 1.7 MHz I²C clock support, 2500 VRMS isolation rating, 3.0–5.5 V dual-supply operation, and –40 to +125 °C temperature range - enabling use in motor control, PoE, and hot-swap power systems.

For engineers reviewing the SI8400AB-A-ISR datasheet, SI8400AB-A-ISR pinout, SI8400AB-A-ISR application, or SI8400AB-A-ISR equivalent, key selection criteria include its SOIC-8 narrow-body package, open-drain SDA/SCL outputs with 35 mA sink capability per side, RF-based isolation architecture, and compliance with UL 1577, CSA 5A, and VDE 0884-2 safety standards.

Technical Context

The SI8400AB-A-ISR implements Skyworks' proprietary RF-based isolation: an on-chip oscillator modulates input signals via on/off keying across a semiconductor barrier, then demodulates them on the output side - delivering superior CMTI (25 kV/µs), low propagation delay (9–29 ns), and immunity to magnetic fields versus optocouplers. It contains independent UVLO monitors on both sides (AVDD/BVDD) with 2.15–2.5 V turn-on thresholds and 45–95 mV hysteresis.

All I²C channels are bidirectional (SDA/SCL), while non-I²C channels are unidirectional CMOS-compatible interfaces with 85 Ω nominal output impedance, 10 Mbps max data rate, and 40 ns minimum pulse width. The device supports hot-swap insertion and includes protection against data corruption when one side is unpowered.

Key Specifications

Pinout & Package

SI8400AB-A-ISR is housed in an 8-pin narrow-body SOIC package (5.3 mm × 6.2 mm, 1.75 mm height) with creepage/clearance ≥4.01 mm and reinforced insulation rated to 560 V_PEAK.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADUM1250ARZ and ISO1540DR, SI8400AB-A-ISR uniquely supports 1.7 MHz I²C operation with guaranteed 25 kV/µs CMTI and full VDE 0884-2 compliance - making it the only option among the three qualified for high-speed, safety-certified industrial and PoE applications.

Availability

SI8400AB-A-ISR is available at Aetrix Electronics and suitable for industrial motor control, Power over Ethernet, and intelligent power systems requiring stable component supply, long-term lifecycle assurance, and regulatory-compliant isolation.

Supply support for SI8400AB-A-ISR 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, isolation, and power management solutions for communications, industrial, and automotive markets.

The Si840x family was engineered specifically to replace optocouplers in I²C/SMBus isolation applications - delivering higher speed, lower power, smaller footprint, and longer reliability than legacy optical solutions.

FAQ

What is the maximum I²C clock frequency supported by the SI8400AB-A-ISR?

The SI8400AB-A-ISR supports a maximum I²C clock frequency of 1.7 MHz, enabling compliance with fast-mode-plus specifications. This performance is validated across the full operating temperature range (–40 to +125 °C) and supply voltage range (3.0–5.5 V). The SI8400AB-A-ISR achieves this using low-propagation-delay RF isolation, unlike slower optocoupler-based alternatives. All timing parameters for 1.7 MHz operation are specified in Table 6 of the official Skyworks datasheet for SI8400AB-A-ISR.

Does the SI8400AB-A-ISR require external pull-up resistors on the I²C lines?

Yes, the SI8400AB-A-ISR requires external pull-up resistors on both SDA and SCL lines on each side (ASDA/ASCL and BSDA/BSCL), as its I²C outputs are open-drain. The device supports up to 35 mA sink current per channel, allowing standard 1 kΩ pull-ups at 3.3 V or 5 V. Pull-up placement must follow I²C bus topology rules - typically near the master - and resistor values should be selected based on bus capacitance and desired rise time. No internal pull-ups are present in SI8400AB-A-ISR.

Is the SI8400AB-A-ISR certified for reinforced insulation under VDE 0884-2?

Yes, the SI8400AB-A-ISR is certified to VDE 0884-2 (IEC 60747-5-2) for reinforced insulation, with a maximum working insulation voltage of 560 V_PEAK. This certification is documented in Skyworks File 5006301-4880-0001 and applies to the SOIC-8 narrow-body package. The device also carries UL 1577 (2500 VRMS) and CSA Component Notice 5A certifications, making SI8400AB-A-ISR suitable for end-equipment requiring multiple international safety approvals.

Can the SI8400AB-A-ISR operate with different supply voltages on Side A and Side B?

Yes, the SI8400AB-A-ISR supports independent supply voltages on AVDD and BVDD within the 3.0–5.5 V range, enabling level translation between 3.3 V and 5 V I²C domains. Each side has its own UVLO circuit (2.15–2.5 V threshold), so asymmetric power sequencing is supported. For example, Side A may be powered at 3.3 V while Side B operates at 5 V - a key capability for interfacing modern MCUs with legacy 5 V peripherals via SI8400AB-A-ISR.

What happens to the I²C outputs of the SI8400AB-A-ISR when one side loses power?

When either AVDD or BVDD falls below UVLO threshold, the corresponding side's I²C outputs (ASDA/ASCL or BSDA/BSCL) enter high-impedance state - preventing bus contention and ensuring safe hot-swap operation. The powered side continues normal I²C communication, and outputs resume correct logic levels within <1 µs after supply restoration. This behavior is explicitly verified in Table 12 of the SI8400AB-A-ISR datasheet and distinguishes it from non-hot-swap isolators that may latch or drive invalid states during brown-out.